Merge remote-tracking branch 'upstream/master' into usermarksusermarks

23 files changed, 1068 insertions, 742 deletions

diff --git a/src/nvim/api/autocmd.c b/src/nvim/api/autocmd.c
index 79ae7994f7..931363e199 100644
--- a/src/nvim/api/autocmd.c
+++ b/src/nvim/api/autocmd.c
@@ -1,8 +1,12 @@
 // This is an open source non-commercial project. Dear PVS-Studio, please check
 // it. PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
 
+#include <assert.h>
 #include <stdbool.h>
+#include <stdint.h>
 #include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
 
 #include "lauxlib.h"
 #include "nvim/api/autocmd.h"
@@ -12,7 +16,12 @@
 #include "nvim/autocmd.h"
 #include "nvim/buffer.h"
 #include "nvim/eval/typval.h"
+#include "nvim/eval/typval_defs.h"
+#include "nvim/ex_cmds_defs.h"
+#include "nvim/globals.h"
 #include "nvim/lua/executor.h"
+#include "nvim/memory.h"
+#include "nvim/vim.h"
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "api/autocmd.c.generated.h"
@@ -38,7 +47,7 @@ static int64_t next_autocmd_id = 1;
 /// Get all autocommands that match the corresponding {opts}.
 ///
 /// These examples will get autocommands matching ALL the given criteria:
-/// <pre>
+/// <pre>lua
 ///   -- Matches all criteria
 ///   autocommands = vim.api.nvim_get_autocmds({
 ///     group = "MyGroup",
@@ -59,6 +68,9 @@ static int64_t next_autocmd_id = 1;
 ///             - group (string|integer): the autocommand group name or id to match against.
 ///             - event (string|array): event or events to match against |autocmd-events|.
 ///             - pattern (string|array): pattern or patterns to match against |autocmd-pattern|.
+///             Cannot be used with {buffer}
+///             - buffer: Buffer number or list of buffer numbers for buffer local autocommands
+///             |autocmd-buflocal|. Cannot be used with {pattern}
 /// @return Array of autocommands matching the criteria, with each item
 ///         containing the following fields:
 ///             - id (number): the autocommand id (only when defined with the API).
@@ -240,7 +252,7 @@ Array nvim_get_autocmds(Dict(get_autocmds) *opts, Error *err)
           assert(pattern_filters[i]);
 
           char *pat = pattern_filters[i];
-          int patlen = (int)STRLEN(pat);
+          int patlen = (int)strlen(pat);
 
           if (aupat_is_buflocal(pat, patlen)) {
             aupat_normalize_buflocal_pat(pattern_buflocal,
@@ -349,82 +361,49 @@ cleanup:
   return autocmd_list;
 }
 
-/// Create an |autocommand|
-///
-/// The API allows for two (mutually exclusive) types of actions to be executed when the autocommand
-/// triggers: a callback function (Lua or Vimscript), or a command (like regular autocommands).
-///
-/// Example using callback:
-/// <pre>
-///     -- Lua function
-///     local myluafun = function() print("This buffer enters") end
-///
-///     -- Vimscript function name (as a string)
-///     local myvimfun = "g:MyVimFunction"
-///
-///     vim.api.nvim_create_autocmd({"BufEnter", "BufWinEnter"}, {
-///       pattern = {"*.c", "*.h"},
-///       callback = myluafun,  -- Or myvimfun
-///     })
-/// </pre>
-///
-/// Lua functions receive a table with information about the autocmd event as an argument. To use
-/// a function which itself accepts another (optional) parameter, wrap the function
-/// in a lambda:
-///
-/// <pre>
-///     -- Lua function with an optional parameter.
-///     -- The autocmd callback would pass a table as argument but this
-///     -- function expects number|nil
-///     local myluafun = function(bufnr) bufnr = bufnr or vim.api.nvim_get_current_buf() end
+/// Creates an |autocommand| event handler, defined by `callback` (Lua function or Vimscript
+/// function _name_ string) or `command` (Ex command string).
 ///
+/// Example using Lua callback:
+/// <pre>lua
 ///     vim.api.nvim_create_autocmd({"BufEnter", "BufWinEnter"}, {
 ///       pattern = {"*.c", "*.h"},
-///       callback = function() myluafun() end,
+///       callback = function(ev)
+///         print(string.format('event fired: %s', vim.inspect(ev)))
+///       end
 ///     })
 /// </pre>
 ///
-/// Example using command:
-/// <pre>
+/// Example using an Ex command as the handler:
+/// <pre>lua
 ///     vim.api.nvim_create_autocmd({"BufEnter", "BufWinEnter"}, {
 ///       pattern = {"*.c", "*.h"},
 ///       command = "echo 'Entering a C or C++ file'",
 ///     })
 /// </pre>
 ///
-/// Example values for pattern:
-/// <pre>
-///   pattern = "*.py"
-///   pattern = { "*.py", "*.pyi" }
-/// </pre>
-///
-/// Example values for event:
-/// <pre>
-///   "BufWritePre"
-///   {"CursorHold", "BufWritePre", "BufWritePost"}
+/// Note: `pattern` is NOT automatically expanded (unlike with |:autocmd|), thus names like "$HOME"
+/// and "~" must be expanded explicitly:
+/// <pre>lua
+///   pattern = vim.fn.expand("~") .. "/some/path/*.py"
 /// </pre>
 ///
-/// @param event (string|array) The event or events to register this autocommand
-/// @param opts Dictionary of autocommand options:
-///             - group (string|integer) optional: the autocommand group name or
-///             id to match against.
-///             - pattern (string|array) optional: pattern or patterns to match
-///             against |autocmd-pattern|.
-///             - buffer (integer) optional: buffer number for buffer local autocommands
+/// @param event (string|array) Event(s) that will trigger the handler (`callback` or `command`).
+/// @param opts Options dict:
+///             - group (string|integer) optional: autocommand group name or id to match against.
+///             - pattern (string|array) optional: pattern(s) to match literally |autocmd-pattern|.
+///             - buffer (integer) optional: buffer number for buffer-local autocommands
 ///             |autocmd-buflocal|. Cannot be used with {pattern}.
-///             - desc (string) optional: description of the autocommand.
-///             - callback (function|string) optional: if a string, the name of a Vimscript function
-///             to call when this autocommand is triggered. Otherwise, a Lua function which is
-///             called when this autocommand is triggered. Cannot be used with {command}. Lua
-///             callbacks can return true to delete the autocommand; in addition, they accept a
-///             single table argument with the following keys:
-///                 - id: (number) the autocommand id
-///                 - event: (string) the name of the event that triggered the autocommand
-///                 |autocmd-events|
-///                 - group: (number|nil) the autocommand group id, if it exists
-///                 - match: (string) the expanded value of |<amatch>|
-///                 - buf: (number) the expanded value of |<abuf>|
-///                 - file: (string) the expanded value of |<afile>|
+///             - desc (string) optional: description (for documentation and troubleshooting).
+///             - callback (function|string) optional: Lua function (or Vimscript function name, if
+///             string) called when the event(s) is triggered. Lua callback can return true to
+///             delete the autocommand, and receives a table argument with these keys:
+///                 - id: (number) autocommand id
+///                 - event: (string) name of the triggered event |autocmd-events|
+///                 - group: (number|nil) autocommand group id, if any
+///                 - match: (string) expanded value of |<amatch>|
+///                 - buf: (number) expanded value of |<abuf>|
+///                 - file: (string) expanded value of |<afile>|
 ///                 - data: (any) arbitrary data passed to |nvim_exec_autocmds()|
 ///             - command (string) optional: Vim command to execute on event. Cannot be used with
 ///             {callback}
@@ -433,7 +412,7 @@ cleanup:
 ///             - nested (boolean) optional: defaults to false. Run nested
 ///             autocommands |autocmd-nested|.
 ///
-/// @return Integer id of the created autocommand.
+/// @return Autocommand id (number)
 /// @see |autocommand|
 /// @see |nvim_del_autocmd()|
 Integer nvim_create_autocmd(uint64_t channel_id, Object event, Dict(create_autocmd) *opts,
@@ -454,8 +433,7 @@ Integer nvim_create_autocmd(uint64_t channel_id, Object event, Dict(create_autoc
   }
 
   if (opts->callback.type != kObjectTypeNil && opts->command.type != kObjectTypeNil) {
-    api_set_error(err, kErrorTypeValidation,
-                  "cannot pass both: 'callback' and 'command' for the same autocmd");
+    api_set_error(err, kErrorTypeValidation, "specify either 'callback' or 'command', not both");
     goto cleanup;
   } else if (opts->callback.type != kObjectTypeNil) {
     // TODO(tjdevries): It's possible we could accept callable tables,
@@ -596,7 +574,7 @@ void nvim_del_autocmd(Integer id, Error *err)
 }
 
 /// Clear all autocommands that match the corresponding {opts}. To delete
-/// a particular autocmd, see |nvim_del_autocmd|.
+/// a particular autocmd, see |nvim_del_autocmd()|.
 /// @param opts Parameters
 ///         - event: (string|table)
 ///              Examples:
@@ -684,7 +662,7 @@ cleanup:
 /// Create or get an autocommand group |autocmd-groups|.
 ///
 /// To get an existing group id, do:
-/// <pre>
+/// <pre>lua
 ///     local id = vim.api.nvim_create_augroup("MyGroup", {
 ///         clear = false
 ///     })
@@ -725,7 +703,7 @@ Integer nvim_create_augroup(uint64_t channel_id, String name, Dict(create_augrou
 ///
 /// To get a group id one can use |nvim_get_autocmds()|.
 ///
-/// NOTE: behavior differs from |augroup-delete|. When deleting a group, autocommands contained in
+/// NOTE: behavior differs from |:augroup-delete|. When deleting a group, autocommands contained in
 /// this group will also be deleted and cleared. This group will no longer exist.
 /// @param id Integer The id of the group.
 /// @see |nvim_del_augroup_by_name()|
@@ -743,10 +721,10 @@ void nvim_del_augroup_by_id(Integer id, Error *err)
 
 /// Delete an autocommand group by name.
 ///
-/// NOTE: behavior differs from |augroup-delete|. When deleting a group, autocommands contained in
+/// NOTE: behavior differs from |:augroup-delete|. When deleting a group, autocommands contained in
 /// this group will also be deleted and cleared. This group will no longer exist.
 /// @param name String The name of the group.
-/// @see |autocommand-groups|
+/// @see |autocmd-groups|
 void nvim_del_augroup_by_name(String name, Error *err)
   FUNC_API_SINCE(9)
 {
@@ -887,12 +865,12 @@ static bool check_autocmd_string_array(Array arr, char *k, Error *err)
 static bool unpack_string_or_array(Array *array, Object *v, char *k, bool required, Error *err)
 {
   if (v->type == kObjectTypeString) {
-    ADD(*array, copy_object(*v));
+    ADD(*array, copy_object(*v, NULL));
   } else if (v->type == kObjectTypeArray) {
     if (!check_autocmd_string_array(v->data.array, k, err)) {
       return false;
     }
-    *array = copy_array(v->data.array);
+    *array = copy_array(v->data.array, NULL);
   } else {
     if (required) {
       api_set_error(err,
@@ -962,7 +940,7 @@ static bool get_patterns_from_pattern_or_buf(Array *patterns, Object pattern, Ob
         patlen = aucmd_pattern_length(pat);
       }
     } else if (v->type == kObjectTypeArray) {
-      if (!check_autocmd_string_array(*patterns, "pattern", err)) {
+      if (!check_autocmd_string_array(v->data.array, "pattern", err)) {
         return false;
       }
 
diff --git a/src/nvim/api/buffer.c b/src/nvim/api/buffer.c
index 5e90e40dd3..fe9e6077d6 100644
--- a/src/nvim/api/buffer.c
+++ b/src/nvim/api/buffer.c
@@ -3,25 +3,30 @@
 
 // Some of this code was adapted from 'if_py_both.h' from the original
 // vim source
+
+#include <assert.h>
 #include <lauxlib.h>
-#include <limits.h>
 #include <stdbool.h>
+#include <stddef.h>
 #include <stdint.h>
-#include <stdlib.h>
+#include <string.h>
 
+#include "klib/kvec.h"
+#include "lua.h"
 #include "nvim/api/buffer.h"
 #include "nvim/api/private/defs.h"
 #include "nvim/api/private/helpers.h"
+#include "nvim/ascii.h"
 #include "nvim/autocmd.h"
 #include "nvim/buffer.h"
+#include "nvim/buffer_defs.h"
 #include "nvim/buffer_updates.h"
 #include "nvim/change.h"
 #include "nvim/cursor.h"
-#include "nvim/decoration.h"
 #include "nvim/drawscreen.h"
 #include "nvim/ex_cmds.h"
-#include "nvim/ex_docmd.h"
 #include "nvim/extmark.h"
+#include "nvim/globals.h"
 #include "nvim/lua/executor.h"
 #include "nvim/mapping.h"
 #include "nvim/mark.h"
@@ -29,9 +34,10 @@
 #include "nvim/memory.h"
 #include "nvim/move.h"
 #include "nvim/ops.h"
+#include "nvim/pos.h"
+#include "nvim/types.h"
 #include "nvim/undo.h"
 #include "nvim/vim.h"
-#include "nvim/window.h"
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "api/buffer.c.generated.h"
@@ -78,7 +84,7 @@ Integer nvim_buf_line_count(Buffer buffer, Error *err)
 ///
 /// Example (Lua): capture buffer updates in a global `events` variable
 /// (use "print(vim.inspect(events))" to see its contents):
-/// <pre>
+/// <pre>lua
 ///   events = {}
 ///   vim.api.nvim_buf_attach(0, false, {
 ///     on_lines=function(...) table.insert(events, {...}) end})
@@ -271,6 +277,7 @@ ArrayOf(String) nvim_buf_get_lines(uint64_t channel_id,
                                    Integer start,
                                    Integer end,
                                    Boolean strict_indexing,
+                                   lua_State *lstate,
                                    Error *err)
   FUNC_API_SINCE(1)
 {
@@ -300,21 +307,18 @@ ArrayOf(String) nvim_buf_get_lines(uint64_t channel_id,
     return rv;
   }
 
-  rv.size = (size_t)(end - start);
-  rv.items = xcalloc(rv.size, sizeof(Object));
+  size_t size = (size_t)(end - start);
+
+  init_line_array(lstate, &rv, size);
 
-  if (!buf_collect_lines(buf, rv.size, start,
-                         (channel_id != VIML_INTERNAL_CALL), &rv, err)) {
+  if (!buf_collect_lines(buf, size, (linenr_T)start, 0, (channel_id != VIML_INTERNAL_CALL), &rv,
+                         lstate, err)) {
     goto end;
   }
 
 end:
   if (ERROR_SET(err)) {
-    for (size_t i = 0; i < rv.size; i++) {
-      xfree(rv.items[i].data.string.data);
-    }
-
-    xfree(rv.items);
+    api_free_array(rv);
     rv.items = NULL;
   }
 
@@ -355,6 +359,8 @@ static bool check_string_array(Array arr, bool disallow_nl, Error *err)
 /// Out-of-bounds indices are clamped to the nearest valid value, unless
 /// `strict_indexing` is set.
 ///
+/// @see |nvim_buf_set_text()|
+///
 /// @param channel_id
 /// @param buffer           Buffer handle, or 0 for current buffer
 /// @param start            First line index
@@ -527,6 +533,8 @@ end:
 ///
 /// Prefer |nvim_buf_set_lines()| if you are only adding or deleting entire lines.
 ///
+/// @see |nvim_buf_set_lines()|
+///
 /// @param channel_id
 /// @param buffer           Buffer handle, or 0 for current buffer
 /// @param start_row        First line index
@@ -570,7 +578,7 @@ void nvim_buf_set_text(uint64_t channel_id, Buffer buffer, Integer start_row, In
   char *str_at_end = NULL;
 
   // Another call to ml_get_buf() may free the line, so make a copy.
-  str_at_start = xstrdup((char *)ml_get_buf(buf, (linenr_T)start_row, false));
+  str_at_start = xstrdup(ml_get_buf(buf, (linenr_T)start_row, false));
   size_t len_at_start = strlen(str_at_start);
   if (start_col < 0 || (size_t)start_col > len_at_start) {
     api_set_error(err, kErrorTypeValidation, "start_col out of bounds");
@@ -578,7 +586,7 @@ void nvim_buf_set_text(uint64_t channel_id, Buffer buffer, Integer start_row, In
   }
 
   // Another call to ml_get_buf() may free the line, so make a copy.
-  str_at_end = xstrdup((char *)ml_get_buf(buf, (linenr_T)end_row, false));
+  str_at_end = xstrdup(ml_get_buf(buf, (linenr_T)end_row, false));
   size_t len_at_end = strlen(str_at_end);
   if (end_col < 0 || (size_t)end_col > len_at_end) {
     api_set_error(err, kErrorTypeValidation, "end_col out of bounds");
@@ -608,7 +616,7 @@ void nvim_buf_set_text(uint64_t channel_id, Buffer buffer, Integer start_row, In
     for (int64_t i = 1; i < end_row - start_row; i++) {
       int64_t lnum = start_row + i;
 
-      const char *bufline = (char *)ml_get_buf(buf, (linenr_T)lnum, false);
+      const char *bufline = ml_get_buf(buf, (linenr_T)lnum, false);
       old_byte += (bcount_t)(strlen(bufline)) + 1;
     }
     old_byte += (bcount_t)end_col + 1;
@@ -786,7 +794,8 @@ early_end:
 ArrayOf(String) nvim_buf_get_text(uint64_t channel_id, Buffer buffer,
                                   Integer start_row, Integer start_col,
                                   Integer end_row, Integer end_col,
-                                  Dictionary opts, Error *err)
+                                  Dictionary opts, lua_State *lstate,
+                                  Error *err)
   FUNC_API_SINCE(9)
 {
   Array rv = ARRAY_DICT_INIT;
@@ -826,33 +835,37 @@ ArrayOf(String) nvim_buf_get_text(uint64_t channel_id, Buffer buffer,
 
   bool replace_nl = (channel_id != VIML_INTERNAL_CALL);
 
+  size_t size = (size_t)(end_row - start_row) + 1;
+
+  init_line_array(lstate, &rv, size);
+
   if (start_row == end_row) {
-    String line = buf_get_text(buf, start_row, start_col, end_col, replace_nl, err);
+    String line = buf_get_text(buf, start_row, start_col, end_col, err);
     if (ERROR_SET(err)) {
-      return rv;
+      goto end;
     }
-
-    ADD(rv, STRING_OBJ(line));
+    push_linestr(lstate, &rv, line.data, line.size, 0, replace_nl);
     return rv;
   }
 
-  rv.size = (size_t)(end_row - start_row) + 1;
-  rv.items = xcalloc(rv.size, sizeof(Object));
+  String str = buf_get_text(buf, start_row, start_col, MAXCOL - 1, err);
+
+  push_linestr(lstate, &rv, str.data, str.size, 0, replace_nl);
 
-  rv.items[0] = STRING_OBJ(buf_get_text(buf, start_row, start_col, MAXCOL - 1, replace_nl, err));
   if (ERROR_SET(err)) {
     goto end;
   }
 
-  if (rv.size > 2) {
-    Array tmp = ARRAY_DICT_INIT;
-    tmp.items = &rv.items[1];
-    if (!buf_collect_lines(buf, rv.size - 2, start_row + 1, replace_nl, &tmp, err)) {
+  if (size > 2) {
+    if (!buf_collect_lines(buf, size - 2, (linenr_T)start_row + 1, 1, replace_nl, &rv, lstate,
+                           err)) {
       goto end;
     }
   }
 
-  rv.items[rv.size - 1] = STRING_OBJ(buf_get_text(buf, end_row, 0, end_col, replace_nl, err));
+  str = buf_get_text(buf, end_row, 0, end_col, err);
+  push_linestr(lstate, &rv, str.data, str.size, (int)(size - 1), replace_nl);
+
   if (ERROR_SET(err)) {
     goto end;
   }
@@ -945,7 +958,7 @@ Integer nvim_buf_get_changedtick(Buffer buffer, Error *err)
 /// @param[out]  err   Error details, if any
 /// @returns Array of |maparg()|-like dictionaries describing mappings.
 ///          The "buffer" key holds the associated buffer handle.
-ArrayOf(Dictionary) nvim_buf_get_keymap(uint64_t channel_id, Buffer buffer, String mode, Error *err)
+ArrayOf(Dictionary) nvim_buf_get_keymap(Buffer buffer, String mode, Error *err)
   FUNC_API_SINCE(3)
 {
   buf_T *buf = find_buffer_by_handle(buffer, err);
@@ -954,7 +967,7 @@ ArrayOf(Dictionary) nvim_buf_get_keymap(uint64_t channel_id, Buffer buffer, Stri
     return (Array)ARRAY_DICT_INIT;
   }
 
-  return keymap_array(mode, buf, channel_id == LUA_INTERNAL_CALL);
+  return keymap_array(mode, buf);
 }
 
 /// Sets a buffer-local |mapping| for the given mode.
@@ -1021,7 +1034,7 @@ void nvim_buf_del_var(Buffer buffer, String name, Error *err)
 /// @param buffer     Buffer handle, or 0 for current buffer
 /// @param[out] err   Error details, if any
 /// @return Buffer name
-String nvim_buf_get_name(Buffer buffer, Error *err)
+String nvim_buf_get_name(Buffer buffer, Arena *arena, Error *err)
   FUNC_API_SINCE(1)
 {
   String rv = STRING_INIT;
@@ -1031,7 +1044,7 @@ String nvim_buf_get_name(Buffer buffer, Error *err)
     return rv;
   }
 
-  return cstr_to_string((char *)buf->b_ffname);
+  return cstr_as_string(buf->b_ffname);
 }
 
 /// Sets the full file name for a buffer
@@ -1386,3 +1399,91 @@ static int64_t normalize_index(buf_T *buf, int64_t index, bool end_exclusive, bo
   index++;
   return index;
 }
+
+/// Initialise a string array either:
+/// - on the Lua stack (as a table) (if lstate is not NULL)
+/// - as an API array object (if lstate is NULL).
+///
+/// @param lstate  Lua state. When NULL the Array is initialized instead.
+/// @param a       Array to initialize
+/// @param size    Size of array
+static inline void init_line_array(lua_State *lstate, Array *a, size_t size)
+{
+  if (lstate) {
+    lua_createtable(lstate, (int)size, 0);
+  } else {
+    a->size = size;
+    a->items = xcalloc(a->size, sizeof(Object));
+  }
+}
+
+/// Push a string onto either the Lua stack (as a table element) or an API array object.
+///
+/// For Lua, a table of the correct size must be created first.
+/// API array objects must be pre allocated.
+///
+/// @param lstate      Lua state. When NULL the Array is pushed to instead.
+/// @param a           Array to push onto when not using Lua
+/// @param s           String to push
+/// @param len         Size of string
+/// @param idx         0-based index to place s
+/// @param replace_nl  Replace newlines ('\n') with null ('\0')
+static void push_linestr(lua_State *lstate, Array *a, const char *s, size_t len, int idx,
+                         bool replace_nl)
+{
+  if (lstate) {
+    // Vim represents NULs as NLs
+    if (s && replace_nl && strchr(s, '\n')) {
+      char *tmp = xmemdupz(s, len);
+      strchrsub(tmp, '\n', '\0');
+      lua_pushlstring(lstate, tmp, len);
+      xfree(tmp);
+    } else {
+      lua_pushlstring(lstate, s, len);
+    }
+    lua_rawseti(lstate, -2, idx + 1);
+  } else {
+    String str = STRING_INIT;
+    if (s) {
+      str = cbuf_to_string(s, len);
+      if (replace_nl) {
+        // Vim represents NULs as NLs, but this may confuse clients.
+        strchrsub(str.data, '\n', '\0');
+      }
+    }
+
+    a->items[idx] = STRING_OBJ(str);
+  }
+}
+
+/// Collects `n` buffer lines into array `l` and/or lua_State `lstate`, optionally replacing
+/// newlines with NUL.
+///
+/// @param buf Buffer to get lines from
+/// @param n Number of lines to collect
+/// @param replace_nl Replace newlines ("\n") with NUL
+/// @param start Line number to start from
+/// @param start_idx First index to push to
+/// @param[out] l If not NULL, Lines are copied here
+/// @param[out] lstate If not NULL, Lines are pushed into a table onto the stack
+/// @param err[out] Error, if any
+/// @return true unless `err` was set
+bool buf_collect_lines(buf_T *buf, size_t n, linenr_T start, int start_idx, bool replace_nl,
+                       Array *l, lua_State *lstate, Error *err)
+{
+  for (size_t i = 0; i < n; i++) {
+    linenr_T lnum = start + (linenr_T)i;
+
+    if (lnum >= MAXLNUM) {
+      if (err != NULL) {
+        api_set_error(err, kErrorTypeValidation, "Line index is too high");
+      }
+      return false;
+    }
+
+    char *bufstr = ml_get_buf(buf, lnum, false);
+    push_linestr(lstate, l, bufstr, strlen(bufstr), start_idx + (int)i, replace_nl);
+  }
+
+  return true;
+}
diff --git a/src/nvim/api/buffer.h b/src/nvim/api/buffer.h
index 1c4a93a587..0814da63cd 100644
--- a/src/nvim/api/buffer.h
+++ b/src/nvim/api/buffer.h
@@ -1,7 +1,10 @@
 #ifndef NVIM_API_BUFFER_H
 #define NVIM_API_BUFFER_H
 
+#include <lauxlib.h>
+
 #include "nvim/api/private/defs.h"
+#include "nvim/buffer_defs.h"
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "api/buffer.h.generated.h"
diff --git a/src/nvim/api/command.c b/src/nvim/api/command.c
index 1323fc347b..abd265f2cf 100644
--- a/src/nvim/api/command.c
+++ b/src/nvim/api/command.c
@@ -1,21 +1,36 @@
 // This is an open source non-commercial project. Dear PVS-Studio, please check
 // it. PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
 
+#include <inttypes.h>
 #include <stdbool.h>
-#include <stdint.h>
-#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
 
+#include "klib/kvec.h"
+#include "lauxlib.h"
 #include "nvim/api/command.h"
-#include "nvim/api/private/converter.h"
 #include "nvim/api/private/defs.h"
 #include "nvim/api/private/helpers.h"
+#include "nvim/ascii.h"
 #include "nvim/autocmd.h"
+#include "nvim/buffer_defs.h"
+#include "nvim/decoration.h"
+#include "nvim/ex_cmds.h"
 #include "nvim/ex_docmd.h"
 #include "nvim/ex_eval.h"
+#include "nvim/garray.h"
+#include "nvim/globals.h"
 #include "nvim/lua/executor.h"
+#include "nvim/macros.h"
+#include "nvim/mbyte.h"
+#include "nvim/memory.h"
 #include "nvim/ops.h"
+#include "nvim/pos.h"
 #include "nvim/regexp.h"
+#include "nvim/strings.h"
+#include "nvim/types.h"
 #include "nvim/usercmd.h"
+#include "nvim/vim.h"
 #include "nvim/window.h"
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS
@@ -31,17 +46,18 @@
 /// @param[out] err  Error details, if any.
 /// @return Dictionary containing command information, with these keys:
 ///         - cmd: (string) Command name.
-///         - range: (array) Command <range>. Can have 0-2 elements depending on how many items the
-///                          range contains. Has no elements if command doesn't accept a range or if
-///                          no range was specified, one element if only a single range item was
-///                          specified and two elements if both range items were specified.
-///         - count: (number) Any |<count>| that was supplied to the command. -1 if command cannot
-///                           take a count.
-///         - reg: (number) The optional command |<register>|, if specified. Empty string if not
-///                         specified or if command cannot take a register.
+///         - range: (array) (optional) Command range (|<line1>| |<line2>|).
+///                          Omitted if command doesn't accept a range.
+///                          Otherwise, has no elements if no range was specified, one element if
+///                          only a single range item was specified, or two elements if both range
+///                          items were specified.
+///         - count: (number) (optional) Command |<count>|.
+///                           Omitted if command cannot take a count.
+///         - reg: (string) (optional) Command |<register>|.
+///                         Omitted if command cannot take a register.
 ///         - bang: (boolean) Whether command contains a |<bang>| (!) modifier.
 ///         - args: (array) Command arguments.
-///         - addr: (string) Value of |:command-addr|. Uses short name.
+///         - addr: (string) Value of |:command-addr|. Uses short name or "line" for -addr=lines.
 ///         - nargs: (string) Value of |:command-nargs|.
 ///         - nextcmd: (string) Next command if there are multiple commands separated by a |:bar|.
 ///                             Empty if there isn't a next command.
@@ -62,13 +78,14 @@
 ///             - browse: (boolean) |:browse|.
 ///             - confirm: (boolean) |:confirm|.
 ///             - hide: (boolean) |:hide|.
+///             - horizontal: (boolean) |:horizontal|.
 ///             - keepalt: (boolean) |:keepalt|.
 ///             - keepjumps: (boolean) |:keepjumps|.
 ///             - keepmarks: (boolean) |:keepmarks|.
 ///             - keeppatterns: (boolean) |:keeppatterns|.
 ///             - lockmarks: (boolean) |:lockmarks|.
 ///             - noswapfile: (boolean) |:noswapfile|.
-///             - tab: (integer) |:tab|.
+///             - tab: (integer) |:tab|. -1 when omitted.
 ///             - verbose: (integer) |:verbose|. -1 when omitted.
 ///             - vertical: (boolean) |:vertical|.
 ///             - split: (string) Split modifier string, is an empty string when there's no split
@@ -104,7 +121,7 @@ Dictionary nvim_parse_cmd(String str, Dictionary opts, Error *err)
 
   // Parse arguments
   Array args = ARRAY_DICT_INIT;
-  size_t length = STRLEN(ea.arg);
+  size_t length = strlen(ea.arg);
 
   // For nargs = 1 or '?', pass the entire argument list as a single argument,
   // otherwise split arguments by whitespace.
@@ -141,15 +158,15 @@ Dictionary nvim_parse_cmd(String str, Dictionary opts, Error *err)
     PUT(result, "cmd", CSTR_TO_OBJ((char *)get_command_name(NULL, ea.cmdidx)));
   }
 
-  if ((ea.argt & EX_RANGE) && ea.addr_count > 0) {
+  if (ea.argt & EX_RANGE) {
     Array range = ARRAY_DICT_INIT;
-    if (ea.addr_count > 1) {
-      ADD(range, INTEGER_OBJ(ea.line1));
+    if (ea.addr_count > 0) {
+      if (ea.addr_count > 1) {
+        ADD(range, INTEGER_OBJ(ea.line1));
+      }
+      ADD(range, INTEGER_OBJ(ea.line2));
     }
-    ADD(range, INTEGER_OBJ(ea.line2));
     PUT(result, "range", ARRAY_OBJ(range));
-  } else {
-    PUT(result, "range", ARRAY_OBJ(ARRAY_DICT_INIT));
   }
 
   if (ea.argt & EX_COUNT) {
@@ -160,14 +177,12 @@ Dictionary nvim_parse_cmd(String str, Dictionary opts, Error *err)
     } else {
       PUT(result, "count", INTEGER_OBJ(0));
     }
-  } else {
-    PUT(result, "count", INTEGER_OBJ(-1));
   }
 
-  char reg[2];
-  reg[0] = (char)ea.regname;
-  reg[1] = '\0';
-  PUT(result, "reg", CSTR_TO_OBJ(reg));
+  if (ea.argt & EX_REGSTR) {
+    char reg[2] = { (char)ea.regname, NUL };
+    PUT(result, "reg", CSTR_TO_OBJ(reg));
+  }
 
   PUT(result, "bang", BOOLEAN_OBJ(ea.forceit));
   PUT(result, "args", ARRAY_OBJ(args));
@@ -238,7 +253,7 @@ Dictionary nvim_parse_cmd(String str, Dictionary opts, Error *err)
   PUT(mods, "unsilent", BOOLEAN_OBJ(cmdinfo.cmdmod.cmod_flags & CMOD_UNSILENT));
   PUT(mods, "sandbox", BOOLEAN_OBJ(cmdinfo.cmdmod.cmod_flags & CMOD_SANDBOX));
   PUT(mods, "noautocmd", BOOLEAN_OBJ(cmdinfo.cmdmod.cmod_flags & CMOD_NOAUTOCMD));
-  PUT(mods, "tab", INTEGER_OBJ(cmdinfo.cmdmod.cmod_tab));
+  PUT(mods, "tab", INTEGER_OBJ(cmdinfo.cmdmod.cmod_tab - 1));
   PUT(mods, "verbose", INTEGER_OBJ(cmdinfo.cmdmod.cmod_verbose - 1));
   PUT(mods, "browse", BOOLEAN_OBJ(cmdinfo.cmdmod.cmod_flags & CMOD_BROWSE));
   PUT(mods, "confirm", BOOLEAN_OBJ(cmdinfo.cmdmod.cmod_flags & CMOD_CONFIRM));
@@ -250,6 +265,7 @@ Dictionary nvim_parse_cmd(String str, Dictionary opts, Error *err)
   PUT(mods, "lockmarks", BOOLEAN_OBJ(cmdinfo.cmdmod.cmod_flags & CMOD_LOCKMARKS));
   PUT(mods, "noswapfile", BOOLEAN_OBJ(cmdinfo.cmdmod.cmod_flags & CMOD_NOSWAPFILE));
   PUT(mods, "vertical", BOOLEAN_OBJ(cmdinfo.cmdmod.cmod_split & WSP_VERT));
+  PUT(mods, "horizontal", BOOLEAN_OBJ(cmdinfo.cmdmod.cmod_split & WSP_HOR));
 
   const char *split;
   if (cmdinfo.cmdmod.cmod_split & WSP_BOT) {
@@ -283,7 +299,11 @@ end:
 /// Unlike |nvim_command()| this command takes a structured Dictionary instead of a String. This
 /// allows for easier construction and manipulation of an Ex command. This also allows for things
 /// such as having spaces inside a command argument, expanding filenames in a command that otherwise
-/// doesn't expand filenames, etc.
+/// doesn't expand filenames, etc. Command arguments may also be Number, Boolean or String.
+///
+/// The first argument may also be used instead of count for commands that support it in order to
+/// make their usage simpler with |vim.cmd()|. For example, instead of
+/// `vim.cmd.bdelete{ count = 2 }`, you may do `vim.cmd.bdelete(2)`.
 ///
 /// On execution error: fails with VimL error, updates v:errmsg.
 ///
@@ -308,8 +328,7 @@ String nvim_cmd(uint64_t channel_id, Dict(cmd) *cmd, Dict(cmd_opts) *opts, Error
 
   char *cmdline = NULL;
   char *cmdname = NULL;
-  ArrayOf(String) args;
-  size_t argc = 0;
+  ArrayOf(String) args = ARRAY_DICT_INIT;
 
   String retv = (String)STRING_INIT;
 
@@ -381,48 +400,70 @@ String nvim_cmd(uint64_t channel_id, Dict(cmd) *cmd, Dict(cmd_opts) *opts, Error
     if (cmd->args.type != kObjectTypeArray) {
       VALIDATION_ERROR("'args' must be an Array");
     }
-    // Check if every argument is valid
+
+    // Process all arguments. Convert non-String arguments to String and check if String arguments
+    // have non-whitespace characters.
     for (size_t i = 0; i < cmd->args.data.array.size; i++) {
       Object elem = cmd->args.data.array.items[i];
-      if (elem.type != kObjectTypeString) {
-        VALIDATION_ERROR("Command argument must be a String");
-      } else if (string_iswhite(elem.data.string)) {
-        VALIDATION_ERROR("Command argument must have non-whitespace characters");
+      char *data_str;
+
+      switch (elem.type) {
+      case kObjectTypeBoolean:
+        data_str = xcalloc(2, sizeof(char));
+        data_str[0] = elem.data.boolean ? '1' : '0';
+        data_str[1] = '\0';
+        break;
+      case kObjectTypeBuffer:
+      case kObjectTypeWindow:
+      case kObjectTypeTabpage:
+      case kObjectTypeInteger:
+        data_str = xcalloc(NUMBUFLEN, sizeof(char));
+        snprintf(data_str, NUMBUFLEN, "%" PRId64, elem.data.integer);
+        break;
+      case kObjectTypeString:
+        if (string_iswhite(elem.data.string)) {
+          VALIDATION_ERROR("String command argument must have at least one non-whitespace "
+                           "character");
+        }
+        data_str = xstrndup(elem.data.string.data, elem.data.string.size);
+        break;
+      default:
+        VALIDATION_ERROR("Invalid type for command argument");
+        break;
       }
+
+      ADD(args, STRING_OBJ(cstr_as_string(data_str)));
     }
 
-    argc = cmd->args.data.array.size;
     bool argc_valid;
 
     // Check if correct number of arguments is used.
     switch (ea.argt & (EX_EXTRA | EX_NOSPC | EX_NEEDARG)) {
     case EX_EXTRA | EX_NOSPC | EX_NEEDARG:
-      argc_valid = argc == 1;
+      argc_valid = args.size == 1;
       break;
     case EX_EXTRA | EX_NOSPC:
-      argc_valid = argc <= 1;
+      argc_valid = args.size <= 1;
       break;
     case EX_EXTRA | EX_NEEDARG:
-      argc_valid = argc >= 1;
+      argc_valid = args.size >= 1;
       break;
     case EX_EXTRA:
       argc_valid = true;
       break;
     default:
-      argc_valid = argc == 0;
+      argc_valid = args.size == 0;
       break;
     }
 
     if (!argc_valid) {
       VALIDATION_ERROR("Incorrect number of arguments supplied");
     }
-
-    args = cmd->args.data.array;
   }
 
   // Simply pass the first argument (if it exists) as the arg pointer to `set_cmd_addr_type()`
   // since it only ever checks the first argument.
-  set_cmd_addr_type(&ea, argc > 0 ? args.items[0].data.string.data : NULL);
+  set_cmd_addr_type(&ea, args.size > 0 ? args.items[0].data.string.data : NULL);
 
   if (HAS_KEY(cmd->range)) {
     if (!(ea.argt & EX_RANGE)) {
@@ -557,15 +598,17 @@ String nvim_cmd(uint64_t channel_id, Dict(cmd) *cmd, Dict(cmd_opts) *opts, Error
     }
 
     if (HAS_KEY(mods.tab)) {
-      if (mods.tab.type != kObjectTypeInteger || mods.tab.data.integer < 0) {
-        VALIDATION_ERROR("'mods.tab' must be a non-negative Integer");
+      if (mods.tab.type != kObjectTypeInteger) {
+        VALIDATION_ERROR("'mods.tab' must be an Integer");
+      } else if ((int)mods.tab.data.integer >= 0) {
+        // Silently ignore negative integers to allow mods.tab to be set to -1.
+        cmdinfo.cmdmod.cmod_tab = (int)mods.tab.data.integer + 1;
       }
-      cmdinfo.cmdmod.cmod_tab = (int)mods.tab.data.integer + 1;
     }
 
     if (HAS_KEY(mods.verbose)) {
       if (mods.verbose.type != kObjectTypeInteger) {
-        VALIDATION_ERROR("'mods.verbose' must be a Integer");
+        VALIDATION_ERROR("'mods.verbose' must be an Integer");
       } else if ((int)mods.verbose.data.integer >= 0) {
         // Silently ignore negative integers to allow mods.verbose to be set to -1.
         cmdinfo.cmdmod.cmod_verbose = (int)mods.verbose.data.integer + 1;
@@ -576,6 +619,10 @@ String nvim_cmd(uint64_t channel_id, Dict(cmd) *cmd, Dict(cmd_opts) *opts, Error
     OBJ_TO_BOOL(vertical, mods.vertical, false, "'mods.vertical'");
     cmdinfo.cmdmod.cmod_split |= (vertical ? WSP_VERT : 0);
 
+    bool horizontal;
+    OBJ_TO_BOOL(horizontal, mods.horizontal, false, "'mods.horizontal'");
+    cmdinfo.cmdmod.cmod_split |= (horizontal ? WSP_HOR : 0);
+
     if (HAS_KEY(mods.split)) {
       if (mods.split.type != kObjectTypeString) {
         VALIDATION_ERROR("'mods.split' must be a String");
@@ -583,15 +630,15 @@ String nvim_cmd(uint64_t channel_id, Dict(cmd) *cmd, Dict(cmd_opts) *opts, Error
 
       if (*mods.split.data.string.data == NUL) {
         // Empty string, do nothing.
-      } else if (STRCMP(mods.split.data.string.data, "aboveleft") == 0
-                 || STRCMP(mods.split.data.string.data, "leftabove") == 0) {
+      } else if (strcmp(mods.split.data.string.data, "aboveleft") == 0
+                 || strcmp(mods.split.data.string.data, "leftabove") == 0) {
         cmdinfo.cmdmod.cmod_split |= WSP_ABOVE;
-      } else if (STRCMP(mods.split.data.string.data, "belowright") == 0
-                 || STRCMP(mods.split.data.string.data, "rightbelow") == 0) {
+      } else if (strcmp(mods.split.data.string.data, "belowright") == 0
+                 || strcmp(mods.split.data.string.data, "rightbelow") == 0) {
         cmdinfo.cmdmod.cmod_split |= WSP_BELOW;
-      } else if (STRCMP(mods.split.data.string.data, "topleft") == 0) {
+      } else if (strcmp(mods.split.data.string.data, "topleft") == 0) {
         cmdinfo.cmdmod.cmod_split |= WSP_TOP;
-      } else if (STRCMP(mods.split.data.string.data, "botright") == 0) {
+      } else if (strcmp(mods.split.data.string.data, "botright") == 0) {
         cmdinfo.cmdmod.cmod_split |= WSP_BOT;
       } else {
         VALIDATION_ERROR("Invalid value for 'mods.split'");
@@ -613,6 +660,12 @@ String nvim_cmd(uint64_t channel_id, Dict(cmd) *cmd, Dict(cmd_opts) *opts, Error
     OBJ_TO_CMOD_FLAG(CMOD_LOCKMARKS, mods.lockmarks, false, "'mods.lockmarks'");
     OBJ_TO_CMOD_FLAG(CMOD_NOSWAPFILE, mods.noswapfile, false, "'mods.noswapfile'");
 
+    if (cmdinfo.cmdmod.cmod_flags & CMOD_ERRSILENT) {
+      // CMOD_ERRSILENT must imply CMOD_SILENT, otherwise apply_cmdmod() and undo_cmdmod() won't
+      // work properly.
+      cmdinfo.cmdmod.cmod_flags |= CMOD_SILENT;
+    }
+
     if ((cmdinfo.cmdmod.cmod_flags & CMOD_SANDBOX) && !(ea.argt & EX_SBOXOK)) {
       VALIDATION_ERROR("Command cannot be run in sandbox");
     }
@@ -620,7 +673,7 @@ String nvim_cmd(uint64_t channel_id, Dict(cmd) *cmd, Dict(cmd_opts) *opts, Error
 
   // Finally, build the command line string that will be stored inside ea.cmdlinep.
   // This also sets the values of ea.cmd, ea.arg, ea.args and ea.arglens.
-  build_cmdline_str(&cmdline, &ea, &cmdinfo, args, argc);
+  build_cmdline_str(&cmdline, &ea, &cmdinfo, args);
   ea.cmdlinep = &cmdline;
 
   garray_T capture_local;
@@ -676,6 +729,7 @@ clear_ga:
     ga_clear(&capture_local);
   }
 end:
+  api_free_array(args);
   xfree(cmdline);
   xfree(cmdname);
   xfree(ea.args);
@@ -705,8 +759,9 @@ static bool string_iswhite(String str)
 
 /// Build cmdline string for command, used by `nvim_cmd()`.
 static void build_cmdline_str(char **cmdlinep, exarg_T *eap, CmdParseInfo *cmdinfo,
-                              ArrayOf(String) args, size_t argc)
+                              ArrayOf(String) args)
 {
+  size_t argc = args.size;
   StringBuilder cmdline = KV_INITIAL_VALUE;
   kv_resize(cmdline, 32);  // Make it big enough to handle most typical commands
 
@@ -753,6 +808,7 @@ static void build_cmdline_str(char **cmdlinep, exarg_T *eap, CmdParseInfo *cmdin
   } while (0)
 
   CMDLINE_APPEND_IF(cmdinfo->cmdmod.cmod_split & WSP_VERT, "vertical ");
+  CMDLINE_APPEND_IF(cmdinfo->cmdmod.cmod_split & WSP_HOR, "horizontal ");
   CMDLINE_APPEND_IF(cmdinfo->cmdmod.cmod_flags & CMOD_SANDBOX, "sandbox ");
   CMDLINE_APPEND_IF(cmdinfo->cmdmod.cmod_flags & CMOD_NOAUTOCMD, "noautocmd ");
   CMDLINE_APPEND_IF(cmdinfo->cmdmod.cmod_flags & CMOD_BROWSE, "browse ");
@@ -791,7 +847,7 @@ static void build_cmdline_str(char **cmdlinep, exarg_T *eap, CmdParseInfo *cmdin
   }
 
   eap->argc = argc;
-  eap->arglens = xcalloc(argc, sizeof(size_t));
+  eap->arglens = eap->argc > 0 ? xcalloc(argc, sizeof(size_t)) : NULL;
   size_t argstart_idx = cmdline.size;
   for (size_t i = 0; i < argc; i++) {
     String s = args.items[i].data.string;
@@ -806,7 +862,7 @@ static void build_cmdline_str(char **cmdlinep, exarg_T *eap, CmdParseInfo *cmdin
   // Now that all the arguments are appended, use the command index and argument indices to set the
   // values of eap->cmd, eap->arg and eap->args.
   eap->cmd = cmdline.items + cmdname_idx;
-  eap->args = xcalloc(argc, sizeof(char *));
+  eap->args = eap->argc > 0 ? xcalloc(argc, sizeof(char *)) : NULL;
   size_t offset = argstart_idx;
   for (size_t i = 0; i < argc; i++) {
     offset++;  // Account for space
@@ -823,13 +879,12 @@ static void build_cmdline_str(char **cmdlinep, exarg_T *eap, CmdParseInfo *cmdin
   // Replace, :make and :grep with 'makeprg' and 'grepprg'.
   char *p = replace_makeprg(eap, eap->arg, cmdlinep);
   if (p != eap->arg) {
-    // If replace_makeprg modified the cmdline string, correct the argument pointers.
+    // If replace_makeprg() modified the cmdline string, correct the eap->arg pointer.
     eap->arg = p;
-    // We can only know the position of the first argument because the argument list can be used
-    // multiple times in makeprg / grepprg.
-    if (argc >= 1) {
-      eap->args[0] = p;
-    }
+    // This cannot be a user command, so eap->args will not be used.
+    XFREE_CLEAR(eap->args);
+    XFREE_CLEAR(eap->arglens);
+    eap->argc = 0;
   }
 }
 
@@ -840,7 +895,7 @@ static void build_cmdline_str(char **cmdlinep, exarg_T *eap, CmdParseInfo *cmdin
 /// {command} is the replacement text or Lua function to execute.
 ///
 /// Example:
-/// <pre>
+/// <pre>vim
 ///    :call nvim_create_user_command('SayHello', 'echo "Hello world!"', {})
 ///    :SayHello
 ///    Hello world!
@@ -850,6 +905,7 @@ static void build_cmdline_str(char **cmdlinep, exarg_T *eap, CmdParseInfo *cmdin
 /// @param  command Replacement command to execute when this user command is executed. When called
 ///                 from Lua, the command can also be a Lua function. The function is called with a
 ///                 single table argument that contains the following keys:
+///                 - name: (string) Command name
 ///                 - args: (string) The args passed to the command, if any |<args>|
 ///                 - fargs: (table) The args split by unescaped whitespace (when more than one
 ///                 argument is allowed), if any |<f-args>|
@@ -929,7 +985,7 @@ void nvim_buf_del_user_command(Buffer buffer, String name, Error *err)
 
   for (int i = 0; i < gap->ga_len; i++) {
     ucmd_T *cmd = USER_CMD_GA(gap, i);
-    if (!STRCMP(name.data, cmd->uc_name)) {
+    if (!strcmp(name.data, cmd->uc_name)) {
       free_ucmd(cmd);
 
       gap->ga_len -= 1;
diff --git a/src/nvim/api/deprecated.c b/src/nvim/api/deprecated.c
index abaac07755..332e2b5fc3 100644
--- a/src/nvim/api/deprecated.c
+++ b/src/nvim/api/deprecated.c
@@ -1,7 +1,6 @@
 // This is an open source non-commercial project. Dear PVS-Studio, please check
 // it. PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
 
-#include <limits.h>
 #include <stdbool.h>
 #include <stdint.h>
 #include <stdlib.h>
@@ -11,10 +10,15 @@
 #include "nvim/api/extmark.h"
 #include "nvim/api/private/defs.h"
 #include "nvim/api/private/helpers.h"
-#include "nvim/api/vim.h"
 #include "nvim/api/vimscript.h"
+#include "nvim/buffer_defs.h"
+#include "nvim/decoration.h"
 #include "nvim/extmark.h"
+#include "nvim/globals.h"
 #include "nvim/lua/executor.h"
+#include "nvim/memory.h"
+#include "nvim/pos.h"
+#include "nvim/types.h"
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "api/deprecated.c.generated.h"
@@ -190,7 +194,7 @@ String buffer_get_line(Buffer buffer, Integer index, Error *err)
   String rv = { .size = 0 };
 
   index = convert_index(index);
-  Array slice = nvim_buf_get_lines(0, buffer, index, index + 1, true, err);
+  Array slice = nvim_buf_get_lines(0, buffer, index, index + 1, true, NULL, err);
 
   if (!ERROR_SET(err) && slice.size) {
     rv = slice.items[0].data.string;
@@ -263,7 +267,7 @@ ArrayOf(String) buffer_get_line_slice(Buffer buffer,
 {
   start = convert_index(start) + !include_start;
   end = convert_index(end) + include_end;
-  return nvim_buf_get_lines(0, buffer, start, end, false, err);
+  return nvim_buf_get_lines(0, buffer, start, end, false, NULL, err);
 }
 
 /// Replaces a line range on the buffer
diff --git a/src/nvim/api/extmark.c b/src/nvim/api/extmark.c
index 933aa85530..ab3b3485e4 100644
--- a/src/nvim/api/extmark.c
+++ b/src/nvim/api/extmark.c
@@ -1,20 +1,29 @@
 // This is an open source non-commercial project. Dear PVS-Studio, please check
 // it. PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
 
+#include <assert.h>
 #include <stdbool.h>
 #include <stdint.h>
-#include <stdlib.h>
+#include <string.h>
 
+#include "klib/kvec.h"
+#include "lauxlib.h"
 #include "nvim/api/extmark.h"
 #include "nvim/api/private/defs.h"
 #include "nvim/api/private/helpers.h"
+#include "nvim/buffer_defs.h"
 #include "nvim/charset.h"
+#include "nvim/decoration.h"
 #include "nvim/decoration_provider.h"
 #include "nvim/drawscreen.h"
 #include "nvim/extmark.h"
 #include "nvim/highlight_group.h"
-#include "nvim/lua/executor.h"
+#include "nvim/mbyte.h"
 #include "nvim/memline.h"
+#include "nvim/memory.h"
+#include "nvim/pos.h"
+#include "nvim/strings.h"
+#include "nvim/vim.h"
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "api/extmark.c.generated.h"
@@ -31,7 +40,7 @@ void api_extmark_free_all_mem(void)
   map_destroy(String, handle_T)(&namespace_ids);
 }
 
-/// Creates a new \*namespace\* or gets an existing one.
+/// Creates a new namespace or gets an existing one. \*namespace\*
 ///
 /// Namespaces are used for buffer highlights and virtual text, see
 /// |nvim_buf_add_highlight()| and |nvim_buf_set_extmark()|.
@@ -51,13 +60,13 @@ Integer nvim_create_namespace(String name)
   }
   id = next_namespace_id++;
   if (name.size > 0) {
-    String name_alloc = copy_string(name);
+    String name_alloc = copy_string(name, NULL);
     map_put(String, handle_T)(&namespace_ids, name_alloc, id);
   }
   return (Integer)id;
 }
 
-/// Gets existing, non-anonymous namespaces.
+/// Gets existing, non-anonymous |namespace|s.
 ///
 /// @return dict that maps from names to namespace ids.
 Dictionary nvim_get_namespaces(void)
@@ -87,7 +96,7 @@ const char *describe_ns(NS ns_id)
 }
 
 // Is the Namespace in use?
-static bool ns_initialized(uint32_t ns)
+bool ns_initialized(uint32_t ns)
 {
   if (ns < 1) {
     return false;
@@ -186,7 +195,7 @@ static Array extmark_to_array(const ExtmarkInfo *extmark, bool id, bool add_dict
   return rv;
 }
 
-/// Gets the position (0-indexed) of an extmark.
+/// Gets the position (0-indexed) of an |extmark|.
 ///
 /// @param buffer  Buffer handle, or 0 for current buffer
 /// @param ns_id  Namespace id from |nvim_create_namespace()|
@@ -240,31 +249,29 @@ ArrayOf(Integer) nvim_buf_get_extmark_by_id(Buffer buffer, Integer ns_id,
   return extmark_to_array(&extmark, false, details);
 }
 
-/// Gets extmarks in "traversal order" from a |charwise| region defined by
+/// Gets |extmarks| in "traversal order" from a |charwise| region defined by
 /// buffer positions (inclusive, 0-indexed |api-indexing|).
 ///
 /// Region can be given as (row,col) tuples, or valid extmark ids (whose
 /// positions define the bounds). 0 and -1 are understood as (0,0) and (-1,-1)
 /// respectively, thus the following are equivalent:
-///
-/// <pre>
-///   nvim_buf_get_extmarks(0, my_ns, 0, -1, {})
-///   nvim_buf_get_extmarks(0, my_ns, [0,0], [-1,-1], {})
+/// <pre>lua
+///   vim.api.nvim_buf_get_extmarks(0, my_ns, 0, -1, {})
+///   vim.api.nvim_buf_get_extmarks(0, my_ns, {0,0}, {-1,-1}, {})
 /// </pre>
 ///
 /// If `end` is less than `start`, traversal works backwards. (Useful
 /// with `limit`, to get the first marks prior to a given position.)
 ///
 /// Example:
-///
-/// <pre>
+/// <pre>lua
 ///   local a   = vim.api
 ///   local pos = a.nvim_win_get_cursor(0)
 ///   local ns  = a.nvim_create_namespace('my-plugin')
 ///   -- Create new extmark at line 1, column 1.
 ///   local m1  = a.nvim_buf_set_extmark(0, ns, 0, 0, {})
 ///   -- Create new extmark at line 3, column 1.
-///   local m2  = a.nvim_buf_set_extmark(0, ns, 0, 2, {})
+///   local m2  = a.nvim_buf_set_extmark(0, ns, 2, 0, {})
 ///   -- Get extmarks only from line 3.
 ///   local ms  = a.nvim_buf_get_extmarks(0, ns, {2,0}, {2,0}, {})
 ///   -- Get all marks in this buffer + namespace.
@@ -361,7 +368,7 @@ Array nvim_buf_get_extmarks(Buffer buffer, Integer ns_id, Object start, Object e
   return rv;
 }
 
-/// Creates or updates an extmark.
+/// Creates or updates an |extmark|.
 ///
 /// By default a new extmark is created when no id is passed in, but it is also
 /// possible to create a new mark by passing in a previously unused id or move
@@ -389,11 +396,11 @@ Array nvim_buf_get_extmarks(Buffer buffer, Integer ns_id, Object start, Object e
 ///               - virt_text : virtual text to link to this mark.
 ///                   A list of [text, highlight] tuples, each representing a
 ///                   text chunk with specified highlight. `highlight` element
-///                   can either be a a single highlight group, or an array of
+///                   can either be a single highlight group, or an array of
 ///                   multiple highlight groups that will be stacked
 ///                   (highest priority last). A highlight group can be supplied
 ///                   either as a string or as an integer, the latter which
-///                   can be obtained using |nvim_get_hl_id_by_name|.
+///                   can be obtained using |nvim_get_hl_id_by_name()|.
 ///               - virt_text_pos : position of virtual text. Possible values:
 ///                 - "eol": right after eol character (default)
 ///                 - "overlay": display over the specified column, without
@@ -430,7 +437,7 @@ Array nvim_buf_get_extmarks(Buffer buffer, Integer ns_id, Object start, Object e
 ///                                     column of the window, bypassing
 ///                                     sign and number columns.
 ///
-///               - ephemeral : for use with |nvim_set_decoration_provider|
+///               - ephemeral : for use with |nvim_set_decoration_provider()|
 ///                   callbacks. The mark will only be used for the current
 ///                   redraw cycle, and not be permantently stored in the
 ///                   buffer.
@@ -473,6 +480,8 @@ Array nvim_buf_get_extmarks(Buffer buffer, Integer ns_id, Object start, Object e
 ///                   When a character is supplied it is used as |:syn-cchar|.
 ///                   "hl_group" is used as highlight for the cchar if provided,
 ///                   otherwise it defaults to |hl-Conceal|.
+///               - spell: boolean indicating that spell checking should be
+///                   performed within this extmark
 ///               - ui_watched: boolean that indicates the mark should be drawn
 ///                   by a UI. When set, the UI will receive win_extmark events.
 ///                   Note: the mark is positioned by virt_text attributes. Can be
@@ -689,7 +698,7 @@ Integer nvim_buf_set_extmark(Buffer buffer, Integer ns_id, Integer line, Integer
   }
 
   if (opts->sign_text.type == kObjectTypeString) {
-    if (!init_sign_text((char **)&decor.sign_text,
+    if (!init_sign_text(&decor.sign_text,
                         opts->sign_text.data.string.data)) {
       api_set_error(err, kErrorTypeValidation, "sign_text is not a valid value");
       goto error;
@@ -719,6 +728,15 @@ Integer nvim_buf_set_extmark(Buffer buffer, Integer ns_id, Integer line, Integer
   bool ephemeral = false;
   OPTION_TO_BOOL(ephemeral, ephemeral, false);
 
+  if (opts->spell.type == kObjectTypeNil) {
+    decor.spell = kNone;
+  } else {
+    bool spell = false;
+    OPTION_TO_BOOL(spell, spell, false);
+    decor.spell = spell ? kTrue : kFalse;
+    has_decor = true;
+  }
+
   OPTION_TO_BOOL(decor.ui_watched, ui_watched, false);
   if (decor.ui_watched) {
     has_decor = true;
@@ -735,7 +753,7 @@ Integer nvim_buf_set_extmark(Buffer buffer, Integer ns_id, Integer line, Integer
       line = buf->b_ml.ml_line_count;
     }
   } else if (line < buf->b_ml.ml_line_count) {
-    len = ephemeral ? MAXCOL : STRLEN(ml_get_buf(buf, (linenr_T)line + 1, false));
+    len = ephemeral ? MAXCOL : strlen(ml_get_buf(buf, (linenr_T)line + 1, false));
   }
 
   if (col == -1) {
@@ -754,7 +772,7 @@ Integer nvim_buf_set_extmark(Buffer buffer, Integer ns_id, Integer line, Integer
 
   if (col2 >= 0) {
     if (line2 >= 0 && line2 < buf->b_ml.ml_line_count) {
-      len = ephemeral ? MAXCOL : STRLEN(ml_get_buf(buf, (linenr_T)line2 + 1, false));
+      len = ephemeral ? MAXCOL : strlen(ml_get_buf(buf, (linenr_T)line2 + 1, false));
     } else if (line2 == buf->b_ml.ml_line_count) {
       // We are trying to add an extmark past final newline
       len = 0;
@@ -796,7 +814,7 @@ error:
   return 0;
 }
 
-/// Removes an extmark.
+/// Removes an |extmark|.
 ///
 /// @param buffer Buffer handle, or 0 for current buffer
 /// @param ns_id Namespace id from |nvim_create_namespace()|
@@ -826,9 +844,8 @@ uint32_t src2ns(Integer *src_id)
   }
   if (*src_id < 0) {
     return (((uint32_t)1) << 31) - 1;
-  } else {
-    return (uint32_t)(*src_id);
   }
+  return (uint32_t)(*src_id);
 }
 
 /// Adds a highlight to buffer.
@@ -912,7 +929,7 @@ Integer nvim_buf_add_highlight(Buffer buffer, Integer ns_id, String hl_group, In
   return ns_id;
 }
 
-/// Clears namespaced objects (highlights, extmarks, virtual text) from
+/// Clears |namespace|d objects (highlights, |extmarks|, virtual text) from
 /// a region.
 ///
 /// Lines are 0-indexed. |api-indexing|  To clear the namespace in the entire
@@ -945,13 +962,13 @@ void nvim_buf_clear_namespace(Buffer buffer, Integer ns_id, Integer line_start,
                 (int)line_end - 1, MAXCOL);
 }
 
-/// Set or change decoration provider for a namespace
+/// Set or change decoration provider for a |namespace|
 ///
 /// This is a very general purpose interface for having lua callbacks
 /// being triggered during the redraw code.
 ///
-/// The expected usage is to set extmarks for the currently
-/// redrawn buffer. |nvim_buf_set_extmark| can be called to add marks
+/// The expected usage is to set |extmarks| for the currently
+/// redrawn buffer. |nvim_buf_set_extmark()| can be called to add marks
 /// on a per-window or per-lines basis. Use the `ephemeral` key to only
 /// use the mark for the current screen redraw (the callback will be called
 /// again for the next redraw ).
@@ -972,20 +989,21 @@ void nvim_buf_clear_namespace(Buffer buffer, Integer ns_id, Integer line_start,
 /// for the moment.
 ///
 /// @param ns_id  Namespace id from |nvim_create_namespace()|
-/// @param opts   Callbacks invoked during redraw:
+/// @param opts  Table of callbacks:
 ///             - on_start: called first on each screen redraw
 ///                 ["start", tick]
-///             - on_buf: called for each buffer being redrawn (before window
-///                 callbacks)
+///             - on_buf: called for each buffer being redrawn (before
+///                 window callbacks)
 ///                 ["buf", bufnr, tick]
-///             - on_win: called when starting to redraw a specific window.
+///             - on_win: called when starting to redraw a
+///                 specific window.
 ///                 ["win", winid, bufnr, topline, botline_guess]
-///             - on_line: called for each buffer line being redrawn. (The
-///                 interaction with fold lines is subject to change)
+///             - on_line: called for each buffer line being redrawn.
+///                 (The interaction with fold lines is subject to change)
 ///                 ["win", winid, bufnr, row]
 ///             - on_end: called at the end of a redraw cycle
 ///                 ["end", tick]
-void nvim_set_decoration_provider(Integer ns_id, DictionaryOf(LuaRef) opts, Error *err)
+void nvim_set_decoration_provider(Integer ns_id, Dict(set_decoration_provider) *opts, Error *err)
   FUNC_API_SINCE(7) FUNC_API_LUA_ONLY
 {
   DecorProvider *p = get_decor_provider((NS)ns_id, true);
@@ -993,41 +1011,36 @@ void nvim_set_decoration_provider(Integer ns_id, DictionaryOf(LuaRef) opts, Erro
   decor_provider_clear(p);
 
   // regardless of what happens, it seems good idea to redraw
-  redraw_all_later(NOT_VALID);  // TODO(bfredl): too soon?
+  redraw_all_later(UPD_NOT_VALID);  // TODO(bfredl): too soon?
 
   struct {
     const char *name;
+    Object *source;
     LuaRef *dest;
   } cbs[] = {
-    { "on_start", &p->redraw_start },
-    { "on_buf", &p->redraw_buf },
-    { "on_win", &p->redraw_win },
-    { "on_line", &p->redraw_line },
-    { "on_end", &p->redraw_end },
-    { "_on_hl_def", &p->hl_def },
-    { NULL, NULL },
+    { "on_start", &opts->on_start, &p->redraw_start },
+    { "on_buf", &opts->on_buf, &p->redraw_buf },
+    { "on_win", &opts->on_win, &p->redraw_win },
+    { "on_line", &opts->on_line, &p->redraw_line },
+    { "on_end", &opts->on_end, &p->redraw_end },
+    { "_on_hl_def", &opts->_on_hl_def, &p->hl_def },
+    { "_on_spell_nav", &opts->_on_spell_nav, &p->spell_nav },
+    { NULL, NULL, NULL },
   };
 
-  for (size_t i = 0; i < opts.size; i++) {
-    String k = opts.items[i].key;
-    Object *v = &opts.items[i].value;
-    size_t j;
-    for (j = 0; cbs[j].name && cbs[j].dest; j++) {
-      if (strequal(cbs[j].name, k.data)) {
-        if (v->type != kObjectTypeLuaRef) {
-          api_set_error(err, kErrorTypeValidation,
-                        "%s is not a function", cbs[j].name);
-          goto error;
-        }
-        *(cbs[j].dest) = v->data.luaref;
-        v->data.luaref = LUA_NOREF;
-        break;
-      }
+  for (size_t i = 0; cbs[i].source && cbs[i].dest && cbs[i].name; i++) {
+    Object *v = cbs[i].source;
+    if (v->type == kObjectTypeNil) {
+      continue;
     }
-    if (!cbs[j].name) {
-      api_set_error(err, kErrorTypeValidation, "unexpected key: %s", k.data);
+
+    if (v->type != kObjectTypeLuaRef) {
+      api_set_error(err, kErrorTypeValidation,
+                    "%s is not a function", cbs[i].name);
       goto error;
     }
+    *(cbs[i].dest) = v->data.luaref;
+    v->data.luaref = LUA_NOREF;
   }
 
   p->active = true;
@@ -1038,7 +1051,7 @@ error:
   decor_provider_clear(p);
 }
 
-/// Gets the line and column of an extmark.
+/// Gets the line and column of an |extmark|.
 ///
 /// Extmarks may be queried by position, name or even special names
 /// in the future such as "cursor".
@@ -1103,7 +1116,7 @@ static int init_sign_text(char **sign_text, char *text)
 {
   char *s;
 
-  char *endp = text + (int)STRLEN(text);
+  char *endp = text + (int)strlen(text);
 
   // Count cells and check for non-printable chars
   int cells = 0;
diff --git a/src/nvim/api/extmark.h b/src/nvim/api/extmark.h
index 74802c6efb..0a627a889c 100644
--- a/src/nvim/api/extmark.h
+++ b/src/nvim/api/extmark.h
@@ -3,7 +3,10 @@
 
 #include "nvim/api/private/defs.h"
 #include "nvim/decoration.h"
+#include "nvim/macros.h"
 #include "nvim/map.h"
+#include "nvim/map_defs.h"
+#include "nvim/types.h"
 
 EXTERN Map(String, handle_T) namespace_ids INIT(= MAP_INIT);
 EXTERN handle_T next_namespace_id INIT(= 1);
diff --git a/src/nvim/api/keysets.lua b/src/nvim/api/keysets.lua
index 6fad52ba75..30dcef6127 100644
--- a/src/nvim/api/keysets.lua
+++ b/src/nvim/api/keysets.lua
@@ -1,8 +1,17 @@
 return {
-  context = {
+  { 'context', {
     "types";
-  };
-  set_extmark = {
+  }};
+  { 'set_decoration_provider', {
+    "on_start";
+    "on_buf";
+    "on_win";
+    "on_line";
+    "on_end";
+    "_on_hl_def";
+    "_on_spell_nav";
+  }};
+  { 'set_extmark', {
     "id";
     "end_line";
     "end_row";
@@ -28,9 +37,10 @@ return {
     "line_hl_group";
     "cursorline_hl_group";
     "conceal";
+    "spell";
     "ui_watched";
-  };
-  keymap = {
+  }};
+  { 'keymap', {
     "noremap";
     "nowait";
     "silent";
@@ -40,11 +50,11 @@ return {
     "callback";
     "desc";
     "replace_keycodes";
-  };
-  get_commands = {
+  }};
+  { 'get_commands', {
     "builtin";
-  };
-  user_command = {
+  }};
+  { 'user_command', {
     "addr";
     "bang";
     "bar";
@@ -57,8 +67,8 @@ return {
     "preview";
     "range";
     "register";
-  };
-  float_config = {
+  }};
+  { 'float_config', {
     "row";
     "col";
     "width";
@@ -71,27 +81,29 @@ return {
     "focusable";
     "zindex";
     "border";
+    "title";
+    "title_pos";
     "style";
     "noautocmd";
-  };
-  runtime = {
+  }};
+  { 'runtime', {
     "is_lua";
     "do_source";
-  };
-  eval_statusline = {
+  }};
+  { 'eval_statusline', {
     "winid";
     "maxwidth";
     "fillchar";
     "highlights";
     "use_winbar";
     "use_tabline";
-  };
-  option = {
+  }};
+  { 'option', {
     "scope";
     "win";
     "buf";
-  };
-  highlight = {
+  }};
+  { 'highlight', {
     "bold";
     "standout";
     "strikethrough";
@@ -102,6 +114,7 @@ return {
     "underdashed";
     "italic";
     "reverse";
+    "altfont";
     "nocombine";
     "default";
     "cterm";
@@ -114,8 +127,10 @@ return {
     "global_link";
     "fallback";
     "blend";
-  };
-  highlight_cterm = {
+    "fg_indexed";
+    "bg_indexed";
+  }};
+  { 'highlight_cterm', {
     "bold";
     "standout";
     "strikethrough";
@@ -126,16 +141,17 @@ return {
     "underdashed";
     "italic";
     "reverse";
+    "altfont";
     "nocombine";
-  };
+  }};
   -- Autocmds
-  clear_autocmds = {
+  { 'clear_autocmds', {
     "buffer";
     "event";
     "group";
     "pattern";
-  };
-  create_autocmd = {
+  }};
+  { 'create_autocmd', {
     "buffer";
     "callback";
     "command";
@@ -144,24 +160,24 @@ return {
     "nested";
     "once";
     "pattern";
-  };
-  exec_autocmds = {
+  }};
+  { 'exec_autocmds', {
     "buffer";
     "group";
     "modeline";
     "pattern";
     "data";
-  };
-  get_autocmds = {
+  }};
+  { 'get_autocmds', {
     "event";
     "group";
     "pattern";
     "buffer";
-  };
-  create_augroup = {
+  }};
+  { 'create_augroup', {
     "clear";
-  };
-  cmd = {
+  }};
+  { 'cmd', {
     "cmd";
     "range";
     "count";
@@ -173,12 +189,12 @@ return {
     "nargs";
     "addr";
     "nextcmd";
-  };
-  cmd_magic = {
+  }};
+  { 'cmd_magic', {
     "file";
     "bar";
-  };
-  cmd_mods = {
+  }};
+  { 'cmd_mods', {
     "silent";
     "emsg_silent";
     "unsilent";
@@ -188,6 +204,7 @@ return {
     "browse";
     "confirm";
     "hide";
+    "horizontal";
     "keepalt";
     "keepjumps";
     "keepmarks";
@@ -198,13 +215,15 @@ return {
     "verbose";
     "vertical";
     "split";
-  };
-  cmd_mods_filter = {
+  }};
+  { 'cmd_mods_filter', {
     "pattern";
     "force";
-  };
-  cmd_opts = {
+  }};
+  { 'cmd_opts', {
     "output";
-  };
+  }};
+  { 'echo_opts', {
+    "verbose";
+  }};
 }
-
diff --git a/src/nvim/api/options.c b/src/nvim/api/options.c
index 867584dd71..bfcb99754f 100644
--- a/src/nvim/api/options.c
+++ b/src/nvim/api/options.c
@@ -1,20 +1,21 @@
 // This is an open source non-commercial project. Dear PVS-Studio, please check
 // it. PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
 
-#include <assert.h>
 #include <inttypes.h>
+#include <limits.h>
 #include <stdbool.h>
-#include <stddef.h>
-#include <stdlib.h>
 #include <string.h>
 
 #include "nvim/api/options.h"
-#include "nvim/api/private/converter.h"
+#include "nvim/api/private/defs.h"
 #include "nvim/api/private/helpers.h"
 #include "nvim/autocmd.h"
-#include "nvim/buffer.h"
+#include "nvim/buffer_defs.h"
+#include "nvim/eval/window.h"
+#include "nvim/globals.h"
+#include "nvim/memory.h"
 #include "nvim/option.h"
-#include "nvim/option_defs.h"
+#include "nvim/vim.h"
 #include "nvim/window.h"
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS
@@ -147,7 +148,7 @@ Object nvim_get_option_value(String name, Dict(option) *opts, Error *err)
 /// @param name      Option name
 /// @param value     New option value
 /// @param opts      Optional parameters
-///                  - scope: One of 'global' or 'local'. Analogous to
+///                  - scope: One of "global" or "local". Analogous to
 ///                  |:setglobal| and |:setlocal|, respectively.
 ///                  - win: |window-ID|. Used for setting window local option.
 ///                  - buf: Buffer number. Used for setting buffer local option.
@@ -202,7 +203,7 @@ void nvim_set_option_value(String name, Object value, Dict(option) *opts, Error
 /// Gets the option information for all options.
 ///
 /// The dictionary has the full option names as keys and option metadata
-/// dictionaries as detailed at |nvim_get_option_info|.
+/// dictionaries as detailed at |nvim_get_option_info()|.
 ///
 /// @return dictionary of all options
 Dictionary nvim_get_all_options_info(Error *err)
@@ -256,7 +257,7 @@ void nvim_set_option(uint64_t channel_id, String name, Object value, Error *err)
 /// @param name     Option name
 /// @param[out] err Error details, if any
 /// @return         Option value (global)
-Object nvim_get_option(String name, Error *err)
+Object nvim_get_option(String name, Arena *arena, Error *err)
   FUNC_API_SINCE(1)
 {
   return get_option_from(NULL, SREQ_GLOBAL, name, err);
@@ -268,7 +269,7 @@ Object nvim_get_option(String name, Error *err)
 /// @param name       Option name
 /// @param[out] err   Error details, if any
 /// @return Option value
-Object nvim_buf_get_option(Buffer buffer, String name, Error *err)
+Object nvim_buf_get_option(Buffer buffer, String name, Arena *arena, Error *err)
   FUNC_API_SINCE(1)
 {
   buf_T *buf = find_buffer_by_handle(buffer, err);
@@ -306,7 +307,7 @@ void nvim_buf_set_option(uint64_t channel_id, Buffer buffer, String name, Object
 /// @param name     Option name
 /// @param[out] err Error details, if any
 /// @return Option value
-Object nvim_win_get_option(Window window, String name, Error *err)
+Object nvim_win_get_option(Window window, String name, Arena *arena, Error *err)
   FUNC_API_SINCE(1)
 {
   win_T *win = find_window_by_handle(window, err);
@@ -346,7 +347,7 @@ void nvim_win_set_option(uint64_t channel_id, Window window, String name, Object
 /// @param name The option name
 /// @param[out] err Details of an error that may have occurred
 /// @return the option value
-Object get_option_from(void *from, int type, String name, Error *err)
+static Object get_option_from(void *from, int type, String name, Error *err)
 {
   Object rv = OBJECT_INIT;
 
@@ -358,8 +359,7 @@ Object get_option_from(void *from, int type, String name, Error *err)
   // Return values
   int64_t numval;
   char *stringval = NULL;
-  int flags = get_option_value_strict(name.data, &numval, &stringval,
-                                      type, from);
+  int flags = get_option_value_strict(name.data, &numval, &stringval, type, from);
 
   if (!flags) {
     api_set_error(err, kErrorTypeValidation, "Invalid option name: '%s'",
@@ -487,7 +487,7 @@ static getoption_T access_option_value(char *key, long *numval, char **stringval
                                        bool get, Error *err)
 {
   if (get) {
-    return get_option_value(key, numval, stringval, opt_flags);
+    return get_option_value(key, numval, stringval, NULL, opt_flags);
   } else {
     char *errmsg;
     if ((errmsg = set_option_value(key, *numval, *stringval, opt_flags))) {
diff --git a/src/nvim/api/private/converter.c b/src/nvim/api/private/converter.c
index 8724ef4432..58ff552ab7 100644
--- a/src/nvim/api/private/converter.c
+++ b/src/nvim/api/private/converter.c
@@ -2,17 +2,24 @@
 // it. PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
 
 #include <assert.h>
+#include <stdbool.h>
 #include <stddef.h>
+#include <stdint.h>
 #include <stdlib.h>
 
+#include "klib/kvec.h"
 #include "nvim/api/private/converter.h"
 #include "nvim/api/private/defs.h"
 #include "nvim/api/private/helpers.h"
 #include "nvim/assert.h"
 #include "nvim/eval/typval.h"
+#include "nvim/eval/typval_defs.h"
 #include "nvim/eval/userfunc.h"
-#include "nvim/lua/converter.h"
+#include "nvim/garray.h"
 #include "nvim/lua/executor.h"
+#include "nvim/memory.h"
+#include "nvim/types.h"
+#include "nvim/vim.h"
 
 /// Helper structure for vim_to_object
 typedef struct {
@@ -65,8 +72,8 @@ typedef struct {
 #define TYPVAL_ENCODE_CONV_FUNC_START(tv, fun) \
   do { \
     ufunc_T *fp = find_func(fun); \
-    if (fp != NULL && fp->uf_cb == nlua_CFunction_func_call) { \
-      LuaRef ref = api_new_luaref(((LuaCFunctionState *)fp->uf_cb_state)->lua_callable.func_ref); \
+    if (fp != NULL && (fp->uf_flags & FC_LUAREF)) { \
+      LuaRef ref = api_new_luaref(fp->uf_luaref); \
       kvi_push(edata->stack, LUAREF_OBJ(ref)); \
     } else { \
       TYPVAL_ENCODE_CONV_NIL(tv); \
@@ -351,10 +358,7 @@ bool object_to_vim(Object obj, typval_T *tv, Error *err)
   }
 
   case kObjectTypeLuaRef: {
-    LuaCFunctionState *state = xmalloc(sizeof(LuaCFunctionState));
-    state->lua_callable.func_ref = api_new_luaref(obj.data.luaref);
-    char *name =
-      (char *)register_cfunc(&nlua_CFunction_func_call, &nlua_CFunction_func_free, state);
+    char *name = register_luafunc(api_new_luaref(obj.data.luaref));
     tv->v_type = VAR_FUNC;
     tv->vval.v_string = xstrdup(name);
     break;
diff --git a/src/nvim/api/private/defs.h b/src/nvim/api/private/defs.h
index 9c7e59e4b3..8acbf0d9de 100644
--- a/src/nvim/api/private/defs.h
+++ b/src/nvim/api/private/defs.h
@@ -5,14 +5,14 @@
 #include <stdint.h>
 #include <string.h>
 
+#include "klib/kvec.h"
 #include "nvim/func_attr.h"
-#include "nvim/lib/kvec.h"
 #include "nvim/types.h"
 
 #define ARRAY_DICT_INIT KV_INITIAL_VALUE
 #define STRING_INIT { .data = NULL, .size = 0 }
 #define OBJECT_INIT { .type = kObjectTypeNil }
-#define ERROR_INIT { .type = kErrorTypeNone, .msg = NULL }
+#define ERROR_INIT ((Error) { .type = kErrorTypeNone, .msg = NULL })
 #define REMOTE_TYPE(type) typedef handle_T type
 
 #define ERROR_SET(e) ((e)->type != kErrorTypeNone)
@@ -48,7 +48,7 @@ typedef enum {
 /// Internal call from lua code
 #define LUA_INTERNAL_CALL (VIML_INTERNAL_CALL + 1)
 
-static inline bool is_internal_call(const uint64_t channel_id)
+static inline bool is_internal_call(uint64_t channel_id)
   REAL_FATTR_ALWAYS_INLINE REAL_FATTR_CONST;
 
 /// Check whether call is internal
diff --git a/src/nvim/api/private/dispatch.c b/src/nvim/api/private/dispatch.c
index d6a6fc1219..f427bba00e 100644
--- a/src/nvim/api/private/dispatch.c
+++ b/src/nvim/api/private/dispatch.c
@@ -1,38 +1,11 @@
 // This is an open source non-commercial project. Dear PVS-Studio, please check
 // it. PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
 
-#include <assert.h>
-#include <inttypes.h>
-#include <msgpack.h>
-#include <stdbool.h>
+#include <stddef.h>
 
-#include "nvim/api/deprecated.h"
 #include "nvim/api/private/defs.h"
 #include "nvim/api/private/dispatch.h"
 #include "nvim/api/private/helpers.h"
-#include "nvim/log.h"
-#include "nvim/map.h"
-#include "nvim/msgpack_rpc/helpers.h"
-#include "nvim/vim.h"
-
-// ===========================================================================
-// NEW API FILES MUST GO HERE.
-//
-//  When creating a new API file, you must include it here,
-//  so that the dispatcher can find the C functions that you are creating!
-// ===========================================================================
-#include "nvim/api/autocmd.h"
-#include "nvim/api/buffer.h"
-#include "nvim/api/command.h"
-#include "nvim/api/extmark.h"
-#include "nvim/api/options.h"
-#include "nvim/api/tabpage.h"
-#include "nvim/api/ui.h"
-#include "nvim/api/vim.h"
-#include "nvim/api/vimscript.h"
-#include "nvim/api/win_config.h"
-#include "nvim/api/window.h"
-#include "nvim/ui_client.h"
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "api/private/dispatch_wrappers.generated.h"
diff --git a/src/nvim/api/private/dispatch.h b/src/nvim/api/private/dispatch.h
index 4b7c394944..4ae61b2bfb 100644
--- a/src/nvim/api/private/dispatch.h
+++ b/src/nvim/api/private/dispatch.h
@@ -1,22 +1,29 @@
 #ifndef NVIM_API_PRIVATE_DISPATCH_H
 #define NVIM_API_PRIVATE_DISPATCH_H
 
+#include <stdbool.h>
+#include <stdint.h>
+
 #include "nvim/api/private/defs.h"
+#include "nvim/memory.h"
+#include "nvim/types.h"
 
-typedef Object (*ApiDispatchWrapper)(uint64_t channel_id,
-                                     Array args,
-                                     Error *error);
+typedef Object (*ApiDispatchWrapper)(uint64_t channel_id, Array args, Arena *arena, Error *error);
 
 /// The rpc_method_handlers table, used in msgpack_rpc_dispatch(), stores
 /// functions of this type.
-typedef struct {
+struct MsgpackRpcRequestHandler {
   const char *name;
   ApiDispatchWrapper fn;
   bool fast;  // Function is safe to be executed immediately while running the
               // uv loop (the loop is run very frequently due to breakcheck).
               // If "fast" is false, the function is deferred, i e the call will
               // be put in the event queue, for safe handling later.
-} MsgpackRpcRequestHandler;
+  bool arena_return;  // return value is allocated in the arena (or statically)
+                      // and should not be freed as such.
+};
+
+extern const MsgpackRpcRequestHandler method_handlers[];
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "api/private/dispatch.h.generated.h"
diff --git a/src/nvim/api/private/helpers.c b/src/nvim/api/private/helpers.c
index c466fc53e1..519f2cc5bf 100644
--- a/src/nvim/api/private/helpers.c
+++ b/src/nvim/api/private/helpers.c
@@ -3,37 +3,36 @@
 
 #include <assert.h>
 #include <inttypes.h>
+#include <limits.h>
+#include <msgpack/unpack.h>
+#include <stdarg.h>
 #include <stdbool.h>
 #include <stddef.h>
+#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
+#include "klib/kvec.h"
 #include "nvim/api/private/converter.h"
 #include "nvim/api/private/defs.h"
 #include "nvim/api/private/helpers.h"
-#include "nvim/api/vim.h"
 #include "nvim/ascii.h"
-#include "nvim/assert.h"
-#include "nvim/buffer.h"
-#include "nvim/charset.h"
-#include "nvim/eval.h"
+#include "nvim/buffer_defs.h"
 #include "nvim/eval/typval.h"
-#include "nvim/ex_cmds_defs.h"
+#include "nvim/eval/typval_defs.h"
 #include "nvim/ex_eval.h"
-#include "nvim/extmark.h"
+#include "nvim/garray.h"
 #include "nvim/highlight_group.h"
-#include "nvim/lib/kvec.h"
 #include "nvim/lua/executor.h"
 #include "nvim/map.h"
-#include "nvim/map_defs.h"
 #include "nvim/mark.h"
 #include "nvim/memline.h"
 #include "nvim/memory.h"
+#include "nvim/message.h"
 #include "nvim/msgpack_rpc/helpers.h"
+#include "nvim/pos.h"
 #include "nvim/ui.h"
 #include "nvim/version.h"
-#include "nvim/vim.h"
-#include "nvim/window.h"
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "api/private/funcs_metadata.generated.h"
@@ -58,6 +57,7 @@ void try_enter(TryState *const tstate)
     .private_msg_list = NULL,
     .trylevel = trylevel,
     .got_int = got_int,
+    .did_throw = did_throw,
     .need_rethrow = need_rethrow,
     .did_emsg = did_emsg,
   };
@@ -65,6 +65,7 @@ void try_enter(TryState *const tstate)
   current_exception = NULL;
   trylevel = 1;
   got_int = false;
+  did_throw = false;
   need_rethrow = false;
   did_emsg = false;
 }
@@ -85,6 +86,7 @@ bool try_leave(const TryState *const tstate, Error *const err)
   assert(trylevel == 0);
   assert(!need_rethrow);
   assert(!got_int);
+  assert(!did_throw);
   assert(!did_emsg);
   assert(msg_list == &tstate->private_msg_list);
   assert(*msg_list == NULL);
@@ -93,6 +95,7 @@ bool try_leave(const TryState *const tstate, Error *const err)
   current_exception = tstate->current_exception;
   trylevel = tstate->trylevel;
   got_int = tstate->got_int;
+  did_throw = tstate->did_throw;
   need_rethrow = tstate->need_rethrow;
   did_emsg = tstate->did_emsg;
   return ret;
@@ -127,7 +130,7 @@ bool try_end(Error *err)
   force_abort = false;
 
   if (got_int) {
-    if (current_exception) {
+    if (did_throw) {
       // If we got an interrupt, discard the current exception
       discard_current_exception();
     }
@@ -146,8 +149,19 @@ bool try_end(Error *err)
     if (should_free) {
       xfree(msg);
     }
-  } else if (current_exception) {
-    api_set_error(err, kErrorTypeException, "%s", current_exception->value);
+  } else if (did_throw) {
+    if (*current_exception->throw_name != NUL) {
+      if (current_exception->throw_lnum != 0) {
+        api_set_error(err, kErrorTypeException, "%s, line %" PRIdLINENR ": %s",
+                      current_exception->throw_name, current_exception->throw_lnum,
+                      current_exception->value);
+      } else {
+        api_set_error(err, kErrorTypeException, "%s: %s",
+                      current_exception->throw_name, current_exception->value);
+      }
+    } else {
+      api_set_error(err, kErrorTypeException, "%s", current_exception->value);
+    }
     discard_current_exception();
   }
 
@@ -214,6 +228,8 @@ Object dict_set_var(dict_T *dict, String key, Object value, bool del, bool retva
     return rv;
   }
 
+  bool watched = tv_dict_is_watched(dict);
+
   if (del) {
     // Delete the key
     if (di == NULL) {
@@ -221,6 +237,10 @@ Object dict_set_var(dict_T *dict, String key, Object value, bool del, bool retva
       api_set_error(err, kErrorTypeValidation, "Key not found: %s",
                     key.data);
     } else {
+      // Notify watchers
+      if (watched) {
+        tv_dict_watcher_notify(dict, key.data, NULL, &di->di_tv);
+      }
       // Return the old value
       if (retval) {
         rv = vim_to_object(&di->di_tv);
@@ -237,11 +257,16 @@ Object dict_set_var(dict_T *dict, String key, Object value, bool del, bool retva
       return rv;
     }
 
+    typval_T oldtv = TV_INITIAL_VALUE;
+
     if (di == NULL) {
       // Need to create an entry
       di = tv_dict_item_alloc_len(key.data, key.size);
       tv_dict_add(dict, di);
     } else {
+      if (watched) {
+        tv_copy(&di->di_tv, &oldtv);
+      }
       // Return the old value
       if (retval) {
         rv = vim_to_object(&di->di_tv);
@@ -251,6 +276,13 @@ Object dict_set_var(dict_T *dict, String key, Object value, bool del, bool retva
 
     // Update the value
     tv_copy(&tv, &di->di_tv);
+
+    // Notify watchers
+    if (watched) {
+      tv_dict_watcher_notify(dict, key.data, &tv, &oldtv);
+      tv_clear(&oldtv);
+    }
+
     // Clear the temporary variable
     tv_clear(&tv);
   }
@@ -369,7 +401,13 @@ String cbuf_to_string(const char *buf, size_t size)
 String cstrn_to_string(const char *str, size_t maxsize)
   FUNC_ATTR_NONNULL_ALL
 {
-  return cbuf_to_string(str, STRNLEN(str, maxsize));
+  return cbuf_to_string(str, strnlen(str, maxsize));
+}
+
+String cstrn_as_string(char *str, size_t maxsize)
+  FUNC_ATTR_NONNULL_ALL
+{
+  return cbuf_as_string(str, strnlen(str, maxsize));
 }
 
 /// Creates a String using the given C string. Unlike
@@ -440,53 +478,15 @@ Array string_to_array(const String input, bool crlf)
   return ret;
 }
 
-/// Collects `n` buffer lines into array `l`, optionally replacing newlines
-/// with NUL.
-///
-/// @param buf Buffer to get lines from
-/// @param n Number of lines to collect
-/// @param replace_nl Replace newlines ("\n") with NUL
-/// @param start Line number to start from
-/// @param[out] l Lines are copied here
-/// @param err[out] Error, if any
-/// @return true unless `err` was set
-bool buf_collect_lines(buf_T *buf, size_t n, int64_t start, bool replace_nl, Array *l, Error *err)
-{
-  for (size_t i = 0; i < n; i++) {
-    int64_t lnum = start + (int64_t)i;
-
-    if (lnum >= MAXLNUM) {
-      if (err != NULL) {
-        api_set_error(err, kErrorTypeValidation, "Line index is too high");
-      }
-      return false;
-    }
-
-    const char *bufstr = (char *)ml_get_buf(buf, (linenr_T)lnum, false);
-    Object str = STRING_OBJ(cstr_to_string(bufstr));
-
-    if (replace_nl) {
-      // Vim represents NULs as NLs, but this may confuse clients.
-      strchrsub(str.data.string.data, '\n', '\0');
-    }
-
-    l->items[i] = str;
-  }
-
-  return true;
-}
-
 /// Returns a substring of a buffer line
 ///
 /// @param buf          Buffer handle
 /// @param lnum         Line number (1-based)
 /// @param start_col    Starting byte offset into line (0-based)
 /// @param end_col      Ending byte offset into line (0-based, exclusive)
-/// @param replace_nl   Replace newlines ('\n') with null ('\0')
 /// @param err          Error object
 /// @return The text between start_col and end_col on line lnum of buffer buf
-String buf_get_text(buf_T *buf, int64_t lnum, int64_t start_col, int64_t end_col, bool replace_nl,
-                    Error *err)
+String buf_get_text(buf_T *buf, int64_t lnum, int64_t start_col, int64_t end_col, Error *err)
 {
   String rv = STRING_INIT;
 
@@ -495,7 +495,7 @@ String buf_get_text(buf_T *buf, int64_t lnum, int64_t start_col, int64_t end_col
     return rv;
   }
 
-  const char *bufstr = (char *)ml_get_buf(buf, (linenr_T)lnum, false);
+  char *bufstr = ml_get_buf(buf, (linenr_T)lnum, false);
   size_t line_length = strlen(bufstr);
 
   start_col = start_col < 0 ? (int64_t)line_length + start_col + 1 : start_col;
@@ -515,12 +515,7 @@ String buf_get_text(buf_T *buf, int64_t lnum, int64_t start_col, int64_t end_col
     return rv;
   }
 
-  rv = cstrn_to_string(&bufstr[start_col], (size_t)(end_col - start_col));
-  if (replace_nl) {
-    strchrsub(rv.data, '\n', '\0');
-  }
-
-  return rv;
+  return cstrn_as_string(&bufstr[start_col], (size_t)(end_col - start_col));
 }
 
 void api_free_string(String value)
@@ -618,6 +613,7 @@ void api_clear_error(Error *value)
   value->type = kErrorTypeNone;
 }
 
+/// @returns a shared value. caller must not modify it!
 Dictionary api_metadata(void)
 {
   static Dictionary metadata = ARRAY_DICT_INIT;
@@ -630,7 +626,7 @@ Dictionary api_metadata(void)
     init_type_metadata(&metadata);
   }
 
-  return copy_object(DICTIONARY_OBJ(metadata)).data.dictionary;
+  return metadata;
 }
 
 static void init_function_metadata(Dictionary *metadata)
@@ -715,36 +711,40 @@ static void init_type_metadata(Dictionary *metadata)
   PUT(*metadata, "types", DICTIONARY_OBJ(types));
 }
 
-String copy_string(String str)
+// all the copy_[object] functions allow arena=NULL,
+// then global allocations are used, and the resulting object
+// should be freed with an api_free_[object] function
+
+String copy_string(String str, Arena *arena)
 {
   if (str.data != NULL) {
-    return (String){ .data = xmemdupz(str.data, str.size), .size = str.size };
+    return (String){ .data = arena_memdupz(arena, str.data, str.size), .size = str.size };
   } else {
     return (String)STRING_INIT;
   }
 }
 
-Array copy_array(Array array)
+Array copy_array(Array array, Arena *arena)
 {
-  Array rv = ARRAY_DICT_INIT;
+  Array rv = arena_array(arena, array.size);
   for (size_t i = 0; i < array.size; i++) {
-    ADD(rv, copy_object(array.items[i]));
+    ADD(rv, copy_object(array.items[i], arena));
   }
   return rv;
 }
 
-Dictionary copy_dictionary(Dictionary dict)
+Dictionary copy_dictionary(Dictionary dict, Arena *arena)
 {
-  Dictionary rv = ARRAY_DICT_INIT;
+  Dictionary rv = arena_dict(arena, dict.size);
   for (size_t i = 0; i < dict.size; i++) {
     KeyValuePair item = dict.items[i];
-    PUT(rv, item.key.data, copy_object(item.value));
+    PUT_C(rv, copy_string(item.key, arena).data, copy_object(item.value, arena));
   }
   return rv;
 }
 
 /// Creates a deep clone of an object
-Object copy_object(Object obj)
+Object copy_object(Object obj, Arena *arena)
 {
   switch (obj.type) {
   case kObjectTypeBuffer:
@@ -757,13 +757,13 @@ Object copy_object(Object obj)
     return obj;
 
   case kObjectTypeString:
-    return STRING_OBJ(copy_string(obj.data.string));
+    return STRING_OBJ(copy_string(obj.data.string, arena));
 
   case kObjectTypeArray:
-    return ARRAY_OBJ(copy_array(obj.data.array));
+    return ARRAY_OBJ(copy_array(obj.data.array, arena));
 
   case kObjectTypeDictionary:
-    return DICTIONARY_OBJ(copy_dictionary(obj.data.dictionary));
+    return DICTIONARY_OBJ(copy_dictionary(obj.data.dictionary, arena));
 
   case kObjectTypeLuaRef:
     return LUAREF_OBJ(api_new_luaref(obj.data.luaref));
@@ -844,7 +844,7 @@ HlMessage parse_hl_msg(Array chunks, Error *err)
       goto free_exit;
     }
 
-    String str = copy_string(chunk.items[0].data.string);
+    String str = copy_string(chunk.items[0].data.string, NULL);
 
     int attr = 0;
     if (chunk.size == 2) {
diff --git a/src/nvim/api/private/helpers.h b/src/nvim/api/private/helpers.h
index 4608554448..ec97ba9ec6 100644
--- a/src/nvim/api/private/helpers.h
+++ b/src/nvim/api/private/helpers.h
@@ -1,11 +1,17 @@
 #ifndef NVIM_API_PRIVATE_HELPERS_H
 #define NVIM_API_PRIVATE_HELPERS_H
 
+#include <stdbool.h>
+#include <stddef.h>
+
+#include "klib/kvec.h"
 #include "nvim/api/private/defs.h"
 #include "nvim/decoration.h"
 #include "nvim/ex_eval_defs.h"
 #include "nvim/getchar.h"
-#include "nvim/lib/kvec.h"
+#include "nvim/globals.h"
+#include "nvim/macros.h"
+#include "nvim/map.h"
 #include "nvim/memory.h"
 #include "nvim/vim.h"
 
@@ -134,6 +140,7 @@ typedef struct {
   const msglist_T *const *msg_list;
   int trylevel;
   int got_int;
+  bool did_throw;
   int need_rethrow;
   int did_emsg;
 } TryState;
diff --git a/src/nvim/api/tabpage.c b/src/nvim/api/tabpage.c
index b81fc3b7d7..21eb326c3b 100644
--- a/src/nvim/api/tabpage.c
+++ b/src/nvim/api/tabpage.c
@@ -2,13 +2,14 @@
 // it. PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
 
 #include <stdbool.h>
-#include <stdint.h>
 #include <stdlib.h>
 
 #include "nvim/api/private/defs.h"
 #include "nvim/api/private/helpers.h"
 #include "nvim/api/tabpage.h"
 #include "nvim/api/vim.h"
+#include "nvim/buffer_defs.h"
+#include "nvim/globals.h"
 #include "nvim/memory.h"
 #include "nvim/window.h"
 
@@ -110,15 +111,14 @@ Window nvim_tabpage_get_win(Tabpage tabpage, Error *err)
 
   if (tab == curtab) {
     return nvim_get_current_win();
-  } else {
-    FOR_ALL_WINDOWS_IN_TAB(wp, tab) {
-      if (wp == tab->tp_curwin) {
-        return wp->handle;
-      }
+  }
+  FOR_ALL_WINDOWS_IN_TAB(wp, tab) {
+    if (wp == tab->tp_curwin) {
+      return wp->handle;
     }
-    // There should always be a current window for a tabpage
-    abort();
   }
+  // There should always be a current window for a tabpage
+  abort();
 }
 
 /// Gets the tabpage number
diff --git a/src/nvim/api/ui.c b/src/nvim/api/ui.c
index 6f7bfa244a..e67607a7e4 100644
--- a/src/nvim/api/ui.c
+++ b/src/nvim/api/ui.c
@@ -2,67 +2,41 @@
 // it. PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
 
 #include <assert.h>
+#include <inttypes.h>
+#include <msgpack/pack.h>
 #include <stdbool.h>
-#include <stddef.h>
 #include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
 
+#include "klib/kvec.h"
 #include "nvim/api/private/defs.h"
 #include "nvim/api/private/helpers.h"
 #include "nvim/api/ui.h"
+#include "nvim/autocmd.h"
 #include "nvim/channel.h"
-#include "nvim/cursor_shape.h"
+#include "nvim/event/loop.h"
+#include "nvim/event/wstream.h"
+#include "nvim/globals.h"
 #include "nvim/grid.h"
 #include "nvim/highlight.h"
+#include "nvim/main.h"
 #include "nvim/map.h"
+#include "nvim/mbyte.h"
 #include "nvim/memory.h"
 #include "nvim/msgpack_rpc/channel.h"
+#include "nvim/msgpack_rpc/channel_defs.h"
 #include "nvim/msgpack_rpc/helpers.h"
 #include "nvim/option.h"
-#include "nvim/popupmenu.h"
+#include "nvim/types.h"
 #include "nvim/ui.h"
 #include "nvim/vim.h"
-#include "nvim/window.h"
-
-typedef struct {
-  uint64_t channel_id;
-
-#define UI_BUF_SIZE 4096  ///< total buffer size for pending msgpack data.
-  /// guaranteed size available for each new event (so packing of simple events
-  /// and the header of grid_line will never fail)
-#define EVENT_BUF_SIZE 256
-  char buf[UI_BUF_SIZE];  ///< buffer of packed but not yet sent msgpack data
-  char *buf_wptr;  ///< write head of buffer
-  const char *cur_event;  ///< name of current event (might get multiple arglists)
-  Array call_buf;  ///< buffer for constructing a single arg list (max 16 elements!)
-
-  // state for write_cb, while packing a single arglist to msgpack. This
-  // might fail due to buffer overflow.
-  size_t pack_totlen;
-  bool buf_overflow;
-  char *temp_buf;
-
-  // We start packing the two outermost msgpack arrays before knowing the total
-  // number of elements. Thus track the location where array size will need
-  // to be written in the msgpack buffer, once the specific array is finished.
-  char *nevents_pos;
-  char *ncalls_pos;
-  uint32_t nevents;  ///< number of distinct events (top-level args to "redraw"
-  uint32_t ncalls;  ///< number of calls made to the current event (plus one for the name!)
-  bool flushed_events;  ///< events where sent to client without "flush" event
-
-  int hl_id;  // Current highlight for legacy put event.
-  Integer cursor_row, cursor_col;  // Intended visible cursor position.
-
-  // Position of legacy cursor, used both for drawing and visible user cursor.
-  Integer client_row, client_col;
-  bool wildmenu_active;
-} UIData;
 
 #define BUF_POS(data) ((size_t)((data)->buf_wptr - (data)->buf))
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "api/ui.c.generated.h"
-# include "ui_events_remote.generated.h"
+# include "ui_events_remote.generated.h"  // IWYU pragma: export
 #endif
 
 static PMap(uint64_t) connected_uis = MAP_INIT;
@@ -122,7 +96,7 @@ static char *mpack_array_dyn16(char **buf)
 static void mpack_str(char **buf, const char *str)
 {
   assert(sizeof(schar_T) - 1 < 0x20);
-  size_t len = STRLEN(str);
+  size_t len = strlen(str);
   mpack_w(buf, 0xa0 | len);
   memcpy(*buf, str, len);
   *buf += len;
@@ -137,8 +111,6 @@ void remote_ui_disconnect(uint64_t channel_id)
   UIData *data = ui->data;
   kv_destroy(data->call_buf);
   pmap_del(uint64_t)(&connected_uis, channel_id);
-  xfree(data);
-  ui->data = NULL;  // Flag UI as "stopped".
   ui_detach_impl(ui, channel_id);
   xfree(ui);
 }
@@ -198,31 +170,6 @@ void nvim_ui_attach(uint64_t channel_id, Integer width, Integer height, Dictiona
   ui->pum_col = -1.0;
   ui->rgb = true;
   ui->override = false;
-  ui->grid_resize = remote_ui_grid_resize;
-  ui->grid_clear = remote_ui_grid_clear;
-  ui->grid_cursor_goto = remote_ui_grid_cursor_goto;
-  ui->mode_info_set = remote_ui_mode_info_set;
-  ui->update_menu = remote_ui_update_menu;
-  ui->busy_start = remote_ui_busy_start;
-  ui->busy_stop = remote_ui_busy_stop;
-  ui->mouse_on = remote_ui_mouse_on;
-  ui->mouse_off = remote_ui_mouse_off;
-  ui->mode_change = remote_ui_mode_change;
-  ui->grid_scroll = remote_ui_grid_scroll;
-  ui->hl_attr_define = remote_ui_hl_attr_define;
-  ui->hl_group_set = remote_ui_hl_group_set;
-  ui->raw_line = remote_ui_raw_line;
-  ui->bell = remote_ui_bell;
-  ui->visual_bell = remote_ui_visual_bell;
-  ui->default_colors_set = remote_ui_default_colors_set;
-  ui->flush = remote_ui_flush;
-  ui->suspend = remote_ui_suspend;
-  ui->set_title = remote_ui_set_title;
-  ui->set_icon = remote_ui_set_icon;
-  ui->option_set = remote_ui_option_set;
-  ui->msg_set_pos = remote_ui_msg_set_pos;
-  ui->event = remote_ui_event;
-  ui->inspect = remote_ui_inspect;
 
   CLEAR_FIELD(ui->ui_ext);
 
@@ -245,7 +192,7 @@ void nvim_ui_attach(uint64_t channel_id, Integer width, Integer height, Dictiona
     ui->ui_ext[kUICmdline] = true;
   }
 
-  UIData *data = xmalloc(sizeof(UIData));
+  UIData *data = ui->data;
   data->channel_id = channel_id;
   data->cur_event = NULL;
   data->hl_id = 0;
@@ -260,7 +207,6 @@ void nvim_ui_attach(uint64_t channel_id, Integer width, Integer height, Dictiona
   data->wildmenu_active = false;
   data->call_buf = (Array)ARRAY_DICT_INIT;
   kv_ensure_space(data->call_buf, 16);
-  ui->data = data;
 
   pmap_put(uint64_t)(&connected_uis, channel_id, ui);
   ui_attach_impl(ui, channel_id);
@@ -276,6 +222,19 @@ void ui_attach(uint64_t channel_id, Integer width, Integer height, Boolean enabl
   api_free_dictionary(opts);
 }
 
+/// Tells the nvim server if focus was gained or lost by the GUI
+void nvim_ui_set_focus(uint64_t channel_id, Boolean gained, Error *error)
+  FUNC_API_SINCE(11) FUNC_API_REMOTE_ONLY
+{
+  if (!pmap_has(uint64_t)(&connected_uis, channel_id)) {
+    api_set_error(error, kErrorTypeException,
+                  "UI not attached to channel: %" PRId64, channel_id);
+    return;
+  }
+
+  do_autocmd_focusgained((bool)gained);
+}
+
 /// Deactivates UI events on the channel.
 ///
 /// Removes the client from the list of UIs. |nvim_list_uis()|
@@ -293,6 +252,10 @@ void nvim_ui_detach(uint64_t channel_id, Error *err)
   remote_ui_disconnect(channel_id);
 }
 
+// TODO(bfredl): use me to detach a specifc ui from the server
+void remote_ui_stop(UI *ui)
+{}
+
 void nvim_ui_try_resize(uint64_t channel_id, Integer width, Integer height, Error *err)
   FUNC_API_SINCE(1) FUNC_API_REMOTE_ONLY
 {
@@ -395,6 +358,24 @@ static void ui_set_option(UI *ui, bool init, String name, Object value, Error *e
     return;
   }
 
+  if (strequal(name.data, "stdin_tty")) {
+    if (value.type != kObjectTypeBoolean) {
+      api_set_error(error, kErrorTypeValidation, "stdin_tty must be a Boolean");
+      return;
+    }
+    stdin_isatty = value.data.boolean;
+    return;
+  }
+
+  if (strequal(name.data, "stdout_tty")) {
+    if (value.type != kObjectTypeBoolean) {
+      api_set_error(error, kErrorTypeValidation, "stdout_tty must be a Boolean");
+      return;
+    }
+    stdout_isatty = value.data.boolean;
+    return;
+  }
+
   // LEGACY: Deprecated option, use `ext_cmdline` instead.
   bool is_popupmenu = strequal(name.data, "popupmenu_external");
 
@@ -452,7 +433,7 @@ void nvim_ui_try_resize_grid(uint64_t channel_id, Integer grid, Integer width, I
   }
 }
 
-/// Tells Nvim the number of elements displaying in the popumenu, to decide
+/// Tells Nvim the number of elements displaying in the popupmenu, to decide
 /// <PageUp> and <PageDown> movement.
 ///
 /// @param channel_id
@@ -482,7 +463,7 @@ void nvim_ui_pum_set_height(uint64_t channel_id, Integer height, Error *err)
   ui->pum_nlines = (int)height;
 }
 
-/// Tells Nvim the geometry of the popumenu, to align floating windows with an
+/// Tells Nvim the geometry of the popupmenu, to align floating windows with an
 /// external popup menu.
 ///
 /// Note that this method is not to be confused with |nvim_ui_pum_set_height()|,
@@ -646,7 +627,7 @@ static void push_call(UI *ui, const char *name, Array args)
   data->ncalls++;
 }
 
-static void remote_ui_grid_clear(UI *ui, Integer grid)
+void remote_ui_grid_clear(UI *ui, Integer grid)
 {
   UIData *data = ui->data;
   Array args = data->call_buf;
@@ -657,7 +638,7 @@ static void remote_ui_grid_clear(UI *ui, Integer grid)
   push_call(ui, name, args);
 }
 
-static void remote_ui_grid_resize(UI *ui, Integer grid, Integer width, Integer height)
+void remote_ui_grid_resize(UI *ui, Integer grid, Integer width, Integer height)
 {
   UIData *data = ui->data;
   Array args = data->call_buf;
@@ -670,8 +651,8 @@ static void remote_ui_grid_resize(UI *ui, Integer grid, Integer width, Integer h
   push_call(ui, name, args);
 }
 
-static void remote_ui_grid_scroll(UI *ui, Integer grid, Integer top, Integer bot, Integer left,
-                                  Integer right, Integer rows, Integer cols)
+void remote_ui_grid_scroll(UI *ui, Integer grid, Integer top, Integer bot, Integer left,
+                           Integer right, Integer rows, Integer cols)
 {
   UIData *data = ui->data;
   if (ui->ui_ext[kUILinegrid]) {
@@ -707,8 +688,8 @@ static void remote_ui_grid_scroll(UI *ui, Integer grid, Integer top, Integer bot
   }
 }
 
-static void remote_ui_default_colors_set(UI *ui, Integer rgb_fg, Integer rgb_bg, Integer rgb_sp,
-                                         Integer cterm_fg, Integer cterm_bg)
+void remote_ui_default_colors_set(UI *ui, Integer rgb_fg, Integer rgb_bg, Integer rgb_sp,
+                                  Integer cterm_fg, Integer cterm_bg)
 {
   if (!ui->ui_ext[kUITermColors]) {
     HL_SET_DEFAULT_COLORS(rgb_fg, rgb_bg, rgb_sp);
@@ -738,8 +719,8 @@ static void remote_ui_default_colors_set(UI *ui, Integer rgb_fg, Integer rgb_bg,
   }
 }
 
-static void remote_ui_hl_attr_define(UI *ui, Integer id, HlAttrs rgb_attrs, HlAttrs cterm_attrs,
-                                     Array info)
+void remote_ui_hl_attr_define(UI *ui, Integer id, HlAttrs rgb_attrs, HlAttrs cterm_attrs,
+                              Array info)
 {
   if (!ui->ui_ext[kUILinegrid]) {
     return;
@@ -748,10 +729,12 @@ static void remote_ui_hl_attr_define(UI *ui, Integer id, HlAttrs rgb_attrs, HlAt
   UIData *data = ui->data;
   Array args = data->call_buf;
   ADD_C(args, INTEGER_OBJ(id));
-  MAXSIZE_TEMP_DICT(rgb, 16);
-  MAXSIZE_TEMP_DICT(cterm, 16);
-  ADD_C(args, DICTIONARY_OBJ(hlattrs2dict(&rgb, rgb_attrs, true)));
-  ADD_C(args, DICTIONARY_OBJ(hlattrs2dict(&cterm, cterm_attrs, false)));
+  MAXSIZE_TEMP_DICT(rgb, HLATTRS_DICT_SIZE);
+  MAXSIZE_TEMP_DICT(cterm, HLATTRS_DICT_SIZE);
+  hlattrs2dict(&rgb, rgb_attrs, true);
+  hlattrs2dict(&cterm, rgb_attrs, false);
+  ADD_C(args, DICTIONARY_OBJ(rgb));
+  ADD_C(args, DICTIONARY_OBJ(cterm));
 
   if (ui->ui_ext[kUIHlState]) {
     ADD_C(args, ARRAY_OBJ(info));
@@ -762,7 +745,7 @@ static void remote_ui_hl_attr_define(UI *ui, Integer id, HlAttrs rgb_attrs, HlAt
   push_call(ui, "hl_attr_define", args);
 }
 
-static void remote_ui_highlight_set(UI *ui, int id)
+void remote_ui_highlight_set(UI *ui, int id)
 {
   UIData *data = ui->data;
   Array args = data->call_buf;
@@ -771,13 +754,14 @@ static void remote_ui_highlight_set(UI *ui, int id)
     return;
   }
   data->hl_id = id;
-  MAXSIZE_TEMP_DICT(dict, 16);
-  ADD_C(args, DICTIONARY_OBJ(hlattrs2dict(&dict, syn_attr2entry(id), ui->rgb)));
+  MAXSIZE_TEMP_DICT(dict, HLATTRS_DICT_SIZE);
+  hlattrs2dict(&dict, syn_attr2entry(id), ui->rgb);
+  ADD_C(args, DICTIONARY_OBJ(dict));
   push_call(ui, "highlight_set", args);
 }
 
 /// "true" cursor used only for input focus
-static void remote_ui_grid_cursor_goto(UI *ui, Integer grid, Integer row, Integer col)
+void remote_ui_grid_cursor_goto(UI *ui, Integer grid, Integer row, Integer col)
 {
   if (ui->ui_ext[kUILinegrid]) {
     UIData *data = ui->data;
@@ -795,7 +779,7 @@ static void remote_ui_grid_cursor_goto(UI *ui, Integer grid, Integer row, Intege
 }
 
 /// emulated cursor used both for drawing and for input focus
-static void remote_ui_cursor_goto(UI *ui, Integer row, Integer col)
+void remote_ui_cursor_goto(UI *ui, Integer row, Integer col)
 {
   UIData *data = ui->data;
   if (data->client_row == row && data->client_col == col) {
@@ -809,7 +793,7 @@ static void remote_ui_cursor_goto(UI *ui, Integer row, Integer col)
   push_call(ui, "cursor_goto", args);
 }
 
-static void remote_ui_put(UI *ui, const char *cell)
+void remote_ui_put(UI *ui, const char *cell)
 {
   UIData *data = ui->data;
   data->client_col++;
@@ -818,9 +802,9 @@ static void remote_ui_put(UI *ui, const char *cell)
   push_call(ui, "put", args);
 }
 
-static void remote_ui_raw_line(UI *ui, Integer grid, Integer row, Integer startcol, Integer endcol,
-                               Integer clearcol, Integer clearattr, LineFlags flags,
-                               const schar_T *chunk, const sattr_T *attrs)
+void remote_ui_raw_line(UI *ui, Integer grid, Integer row, Integer startcol, Integer endcol,
+                        Integer clearcol, Integer clearattr, LineFlags flags, const schar_T *chunk,
+                        const sattr_T *attrs)
 {
   UIData *data = ui->data;
   if (ui->ui_ext[kUILinegrid]) {
@@ -841,7 +825,7 @@ static void remote_ui_raw_line(UI *ui, Integer grid, Integer row, Integer startc
     for (size_t i = 0; i < ncells; i++) {
       repeat++;
       if (i == ncells - 1 || attrs[i] != attrs[i + 1]
-          || STRCMP(chunk[i], chunk[i + 1])) {
+          || strcmp(chunk[i], chunk[i + 1]) != 0) {
         if (UI_BUF_SIZE - BUF_POS(data) < 2 * (1 + 2 + sizeof(schar_T) + 5 + 5)) {
           // close to overflowing the redraw buffer. finish this event,
           // flush, and start a new "grid_line" event at the current position.
@@ -912,7 +896,7 @@ static void remote_ui_raw_line(UI *ui, Integer grid, Integer row, Integer startc
 ///
 /// This might happen multiple times before the actual ui_flush, if the
 /// total redraw size is large!
-static void remote_ui_flush_buf(UI *ui)
+void remote_ui_flush_buf(UI *ui)
 {
   UIData *data = ui->data;
   if (!data->nevents_pos) {
@@ -939,7 +923,7 @@ static void remote_ui_flush_buf(UI *ui)
 ///
 /// Clients can know this happened by a final "flush" event at the end of the
 /// "redraw" batch.
-static void remote_ui_flush(UI *ui)
+void remote_ui_flush(UI *ui)
 {
   UIData *data = ui->data;
   if (data->nevents > 0 || data->flushed_events) {
@@ -952,65 +936,63 @@ static void remote_ui_flush(UI *ui)
   }
 }
 
-static Array translate_contents(UI *ui, Array contents)
+static Array translate_contents(UI *ui, Array contents, Arena *arena)
 {
-  Array new_contents = ARRAY_DICT_INIT;
+  Array new_contents = arena_array(arena, contents.size);
   for (size_t i = 0; i < contents.size; i++) {
     Array item = contents.items[i].data.array;
-    Array new_item = ARRAY_DICT_INIT;
+    Array new_item = arena_array(arena, 2);
     int attr = (int)item.items[0].data.integer;
     if (attr) {
-      Dictionary rgb_attrs = hlattrs2dict(NULL, syn_attr2entry(attr), ui->rgb);
+      Dictionary rgb_attrs = arena_dict(arena, HLATTRS_DICT_SIZE);
+      hlattrs2dict(&rgb_attrs, syn_attr2entry(attr), ui->rgb);
       ADD(new_item, DICTIONARY_OBJ(rgb_attrs));
     } else {
       ADD(new_item, DICTIONARY_OBJ((Dictionary)ARRAY_DICT_INIT));
     }
-    ADD(new_item, copy_object(item.items[1]));
+    ADD(new_item, item.items[1]);
     ADD(new_contents, ARRAY_OBJ(new_item));
   }
   return new_contents;
 }
 
-static Array translate_firstarg(UI *ui, Array args)
+static Array translate_firstarg(UI *ui, Array args, Arena *arena)
 {
-  Array new_args = ARRAY_DICT_INIT;
+  Array new_args = arena_array(arena, args.size);
   Array contents = args.items[0].data.array;
 
-  ADD(new_args, ARRAY_OBJ(translate_contents(ui, contents)));
+  ADD_C(new_args, ARRAY_OBJ(translate_contents(ui, contents, arena)));
   for (size_t i = 1; i < args.size; i++) {
-    ADD(new_args, copy_object(args.items[i]));
+    ADD(new_args, args.items[i]);
   }
   return new_args;
 }
 
-static void remote_ui_event(UI *ui, char *name, Array args)
+void remote_ui_event(UI *ui, char *name, Array args)
 {
+  Arena arena = ARENA_EMPTY;
   UIData *data = ui->data;
   if (!ui->ui_ext[kUILinegrid]) {
     // the representation of highlights in cmdline changed, translate back
     // never consumes args
     if (strequal(name, "cmdline_show")) {
-      Array new_args = translate_firstarg(ui, args);
+      Array new_args = translate_firstarg(ui, args, &arena);
       push_call(ui, name, new_args);
-      api_free_array(new_args);
-      return;
+      goto free_ret;
     } else if (strequal(name, "cmdline_block_show")) {
       Array new_args = data->call_buf;
       Array block = args.items[0].data.array;
-      Array new_block = ARRAY_DICT_INIT;
+      Array new_block = arena_array(&arena, block.size);
       for (size_t i = 0; i < block.size; i++) {
-        ADD(new_block,
-            ARRAY_OBJ(translate_contents(ui, block.items[i].data.array)));
+        ADD_C(new_block, ARRAY_OBJ(translate_contents(ui, block.items[i].data.array, &arena)));
       }
       ADD_C(new_args, ARRAY_OBJ(new_block));
       push_call(ui, name, new_args);
-      api_free_array(new_block);
-      return;
+      goto free_ret;
     } else if (strequal(name, "cmdline_block_append")) {
-      Array new_args = translate_firstarg(ui, args);
+      Array new_args = translate_firstarg(ui, args, &arena);
       push_call(ui, name, new_args);
-      api_free_array(new_args);
-      return;
+      goto free_ret;
     }
   }
 
@@ -1022,19 +1004,18 @@ static void remote_ui_event(UI *ui, char *name, Array args)
       if (data->wildmenu_active) {
         Array new_args = data->call_buf;
         Array items = args.items[0].data.array;
-        Array new_items = ARRAY_DICT_INIT;
+        Array new_items = arena_array(&arena, items.size);
         for (size_t i = 0; i < items.size; i++) {
-          ADD(new_items, copy_object(items.items[i].data.array.items[0]));
+          ADD_C(new_items, items.items[i].data.array.items[0]);
         }
         ADD_C(new_args, ARRAY_OBJ(new_items));
         push_call(ui, "wildmenu_show", new_args);
-        api_free_array(new_items);
         if (args.items[1].data.integer != -1) {
           Array new_args2 = data->call_buf;
           ADD_C(new_args2, args.items[1]);
           push_call(ui, "wildmenu_select", new_args2);
         }
-        return;
+        goto free_ret;
       }
     } else if (strequal(name, "popupmenu_select")) {
       if (data->wildmenu_active) {
@@ -1048,9 +1029,13 @@ static void remote_ui_event(UI *ui, char *name, Array args)
   }
 
   push_call(ui, name, args);
+  return;
+
+free_ret:
+  arena_mem_free(arena_finish(&arena));
 }
 
-static void remote_ui_inspect(UI *ui, Dictionary *info)
+void remote_ui_inspect(UI *ui, Dictionary *info)
 {
   UIData *data = ui->data;
   PUT(*info, "chan", INTEGER_OBJ((Integer)data->channel_id));
diff --git a/src/nvim/api/ui.h b/src/nvim/api/ui.h
index bc70406acb..b3fe0fa2bb 100644
--- a/src/nvim/api/ui.h
+++ b/src/nvim/api/ui.h
@@ -5,8 +5,10 @@
 
 #include "nvim/api/private/defs.h"
 #include "nvim/map.h"
+#include "nvim/ui.h"
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "api/ui.h.generated.h"
+# include "ui_events_remote.h.generated.h"
 #endif
 #endif  // NVIM_API_UI_H
diff --git a/src/nvim/api/ui_events.in.h b/src/nvim/api/ui_events.in.h
index 8b7e01e1c3..a08e8dbfeb 100644
--- a/src/nvim/api/ui_events.in.h
+++ b/src/nvim/api/ui_events.in.h
@@ -31,15 +31,15 @@ void visual_bell(void)
 void flush(void)
   FUNC_API_SINCE(3) FUNC_API_REMOTE_IMPL;
 void suspend(void)
-  FUNC_API_SINCE(3) FUNC_API_BRIDGE_IMPL;
+  FUNC_API_SINCE(3);
 void set_title(String title)
   FUNC_API_SINCE(3);
 void set_icon(String icon)
   FUNC_API_SINCE(3);
 void screenshot(String path)
-  FUNC_API_SINCE(7) FUNC_API_REMOTE_IMPL;
+  FUNC_API_SINCE(7);
 void option_set(String name, Object value)
-  FUNC_API_SINCE(4) FUNC_API_BRIDGE_IMPL;
+  FUNC_API_SINCE(4);
 // Stop event is not exported as such, represented by EOF in the msgpack stream.
 void stop(void)
   FUNC_API_NOEXPORT;
@@ -69,14 +69,13 @@ void scroll(Integer count)
   FUNC_API_SINCE(3) FUNC_API_REMOTE_ONLY;
 
 // Second revision of the grid protocol, used with ext_linegrid ui option
-void default_colors_set(Integer rgb_fg, Integer rgb_bg, Integer rgb_sp,
-                        Integer cterm_fg, Integer cterm_bg)
+void default_colors_set(Integer rgb_fg, Integer rgb_bg, Integer rgb_sp, Integer cterm_fg,
+                        Integer cterm_bg)
   FUNC_API_SINCE(4) FUNC_API_REMOTE_IMPL;
-void hl_attr_define(Integer id, HlAttrs rgb_attrs, HlAttrs cterm_attrs,
-                    Array info)
-  FUNC_API_SINCE(5) FUNC_API_REMOTE_IMPL FUNC_API_BRIDGE_IMPL;
+void hl_attr_define(Integer id, HlAttrs rgb_attrs, HlAttrs cterm_attrs, Array info)
+  FUNC_API_SINCE(5) FUNC_API_REMOTE_IMPL;
 void hl_group_set(String name, Integer id)
-  FUNC_API_SINCE(6) FUNC_API_BRIDGE_IMPL;
+  FUNC_API_SINCE(6) FUNC_API_CLIENT_IGNORE;
 void grid_resize(Integer grid, Integer width, Integer height)
   FUNC_API_SINCE(5) FUNC_API_REMOTE_IMPL FUNC_API_COMPOSITOR_IMPL FUNC_API_CLIENT_IMPL;
 void grid_clear(Integer grid)
@@ -85,8 +84,8 @@ void grid_cursor_goto(Integer grid, Integer row, Integer col)
   FUNC_API_SINCE(5) FUNC_API_REMOTE_IMPL FUNC_API_COMPOSITOR_IMPL;
 void grid_line(Integer grid, Integer row, Integer col_start, Array data)
   FUNC_API_SINCE(5) FUNC_API_REMOTE_ONLY FUNC_API_CLIENT_IMPL;
-void grid_scroll(Integer grid, Integer top, Integer bot,
-                 Integer left, Integer right, Integer rows, Integer cols)
+void grid_scroll(Integer grid, Integer top, Integer bot, Integer left, Integer right, Integer rows,
+                 Integer cols)
   FUNC_API_SINCE(5) FUNC_API_REMOTE_IMPL FUNC_API_COMPOSITOR_IMPL;
 void grid_destroy(Integer grid)
   FUNC_API_SINCE(6) FUNC_API_REMOTE_ONLY;
@@ -94,20 +93,15 @@ void grid_destroy(Integer grid)
 // For performance and simplicity, we use the dense screen representation
 // in internal code, such as compositor and TUI. The remote_ui module will
 // translate this in to the public grid_line format.
-void raw_line(Integer grid, Integer row, Integer startcol,
-              Integer endcol, Integer clearcol, Integer clearattr,
-              LineFlags flags, const schar_T *chunk, const sattr_T *attrs)
+void raw_line(Integer grid, Integer row, Integer startcol, Integer endcol, Integer clearcol,
+              Integer clearattr, LineFlags flags, const schar_T *chunk, const sattr_T *attrs)
   FUNC_API_NOEXPORT FUNC_API_COMPOSITOR_IMPL;
 
-void event(char *name, Array args)
-  FUNC_API_NOEXPORT;
-
-void win_pos(Integer grid, Window win, Integer startrow,
-             Integer startcol, Integer width, Integer height)
+void win_pos(Integer grid, Window win, Integer startrow, Integer startcol, Integer width,
+             Integer height)
   FUNC_API_SINCE(6) FUNC_API_REMOTE_ONLY;
-void win_float_pos(Integer grid, Window win, String anchor, Integer anchor_grid,
-                   Float anchor_row, Float anchor_col, Boolean focusable,
-                   Integer zindex)
+void win_float_pos(Integer grid, Window win, String anchor, Integer anchor_grid, Float anchor_row,
+                   Float anchor_col, Boolean focusable, Integer zindex)
   FUNC_API_SINCE(6) FUNC_API_REMOTE_ONLY;
 void win_external_pos(Integer grid, Window win)
   FUNC_API_SINCE(6) FUNC_API_REMOTE_ONLY;
@@ -115,32 +109,29 @@ void win_hide(Integer grid)
   FUNC_API_SINCE(6) FUNC_API_REMOTE_ONLY;
 void win_close(Integer grid)
   FUNC_API_SINCE(6) FUNC_API_REMOTE_ONLY;
+
 void msg_set_pos(Integer grid, Integer row, Boolean scrolled, String sep_char)
-  FUNC_API_SINCE(6) FUNC_API_BRIDGE_IMPL FUNC_API_COMPOSITOR_IMPL;
+  FUNC_API_SINCE(6) FUNC_API_COMPOSITOR_IMPL FUNC_API_CLIENT_IGNORE;
 
-void win_viewport(Integer grid, Window win, Integer topline,
-                  Integer botline, Integer curline, Integer curcol,
-                  Integer line_count)
-  FUNC_API_SINCE(7) FUNC_API_REMOTE_ONLY;
+void win_viewport(Integer grid, Window win, Integer topline, Integer botline, Integer curline,
+                  Integer curcol, Integer line_count)
+  FUNC_API_SINCE(7) FUNC_API_CLIENT_IGNORE;
 
-void win_extmark(Integer grid, Window win, Integer ns_id, Integer mark_id,
-                 Integer row, Integer col)
+void win_extmark(Integer grid, Window win, Integer ns_id, Integer mark_id, Integer row, Integer col)
   FUNC_API_SINCE(10) FUNC_API_REMOTE_ONLY;
 
-void popupmenu_show(Array items, Integer selected,
-                    Integer row, Integer col, Integer grid)
+void popupmenu_show(Array items, Integer selected, Integer row, Integer col, Integer grid)
   FUNC_API_SINCE(3) FUNC_API_REMOTE_ONLY;
 void popupmenu_hide(void)
   FUNC_API_SINCE(3) FUNC_API_REMOTE_ONLY;
 void popupmenu_select(Integer selected)
   FUNC_API_SINCE(3) FUNC_API_REMOTE_ONLY;
 
-void tabline_update(Tabpage current, Array tabs,
-                    Buffer current_buffer, Array buffers)
+void tabline_update(Tabpage current, Array tabs, Buffer current_buffer, Array buffers)
   FUNC_API_SINCE(3) FUNC_API_REMOTE_ONLY;
 
-void cmdline_show(Array content, Integer pos, String firstc, String prompt,
-                  Integer indent, Integer level)
+void cmdline_show(Array content, Integer pos, String firstc, String prompt, Integer indent,
+                  Integer level)
   FUNC_API_SINCE(3) FUNC_API_REMOTE_ONLY;
 void cmdline_pos(Integer pos, Integer level)
   FUNC_API_SINCE(3) FUNC_API_REMOTE_ONLY;
@@ -156,11 +147,11 @@ void cmdline_block_hide(void)
   FUNC_API_SINCE(3) FUNC_API_REMOTE_ONLY;
 
 void wildmenu_show(Array items)
-  FUNC_API_SINCE(3) FUNC_API_REMOTE_IMPL FUNC_API_BRIDGE_IMPL;
+  FUNC_API_SINCE(3) FUNC_API_REMOTE_ONLY;
 void wildmenu_select(Integer selected)
-  FUNC_API_SINCE(3) FUNC_API_REMOTE_IMPL FUNC_API_BRIDGE_IMPL;
+  FUNC_API_SINCE(3) FUNC_API_REMOTE_ONLY;
 void wildmenu_hide(void)
-  FUNC_API_SINCE(3) FUNC_API_REMOTE_IMPL FUNC_API_BRIDGE_IMPL;
+  FUNC_API_SINCE(3) FUNC_API_REMOTE_ONLY;
 
 void msg_show(String kind, Array content, Boolean replace_last)
   FUNC_API_SINCE(6) FUNC_API_REMOTE_ONLY;
diff --git a/src/nvim/api/vim.c b/src/nvim/api/vim.c
index ce91c1b4af..a53b30dd8a 100644
--- a/src/nvim/api/vim.c
+++ b/src/nvim/api/vim.c
@@ -5,9 +5,13 @@
 #include <inttypes.h>
 #include <limits.h>
 #include <stdbool.h>
+#include <stddef.h>
+#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
+#include "klib/kvec.h"
+#include "lauxlib.h"
 #include "nvim/api/buffer.h"
 #include "nvim/api/deprecated.h"
 #include "nvim/api/private/converter.h"
@@ -15,58 +19,55 @@
 #include "nvim/api/private/dispatch.h"
 #include "nvim/api/private/helpers.h"
 #include "nvim/api/vim.h"
-#include "nvim/api/window.h"
 #include "nvim/ascii.h"
+#include "nvim/autocmd.h"
 #include "nvim/buffer.h"
-#include "nvim/buffer_defs.h"
-#include "nvim/charset.h"
+#include "nvim/channel.h"
 #include "nvim/context.h"
-#include "nvim/decoration.h"
-#include "nvim/decoration_provider.h"
 #include "nvim/drawscreen.h"
-#include "nvim/edit.h"
 #include "nvim/eval.h"
 #include "nvim/eval/typval.h"
-#include "nvim/eval/userfunc.h"
-#include "nvim/ex_cmds_defs.h"
+#include "nvim/eval/typval_defs.h"
 #include "nvim/ex_docmd.h"
 #include "nvim/ex_eval.h"
-#include "nvim/file_search.h"
-#include "nvim/fileio.h"
 #include "nvim/getchar.h"
 #include "nvim/globals.h"
 #include "nvim/grid.h"
 #include "nvim/highlight.h"
-#include "nvim/highlight_defs.h"
 #include "nvim/highlight_group.h"
-#include "nvim/insexpand.h"
+#include "nvim/keycodes.h"
+#include "nvim/log.h"
 #include "nvim/lua/executor.h"
+#include "nvim/macros.h"
 #include "nvim/mapping.h"
 #include "nvim/mark.h"
+#include "nvim/mbyte.h"
 #include "nvim/memline.h"
 #include "nvim/memory.h"
 #include "nvim/message.h"
 #include "nvim/move.h"
 #include "nvim/msgpack_rpc/channel.h"
-#include "nvim/msgpack_rpc/helpers.h"
+#include "nvim/msgpack_rpc/channel_defs.h"
 #include "nvim/msgpack_rpc/unpacker.h"
 #include "nvim/ops.h"
 #include "nvim/option.h"
 #include "nvim/optionstr.h"
 #include "nvim/os/input.h"
+#include "nvim/os/os_defs.h"
 #include "nvim/os/process.h"
 #include "nvim/popupmenu.h"
+#include "nvim/pos.h"
 #include "nvim/runtime.h"
 #include "nvim/state.h"
 #include "nvim/statusline.h"
+#include "nvim/strings.h"
+#include "nvim/terminal.h"
 #include "nvim/types.h"
 #include "nvim/ui.h"
 #include "nvim/vim.h"
-#include "nvim/viml/parser/expressions.h"
-#include "nvim/viml/parser/parser.h"
 #include "nvim/window.h"
 
-#define LINE_BUFFER_SIZE 4096
+#define LINE_BUFFER_MIN_SIZE 4096
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "api/vim.c.generated.h"
@@ -79,19 +80,17 @@
 /// @param[out] err Error details, if any
 /// @return Highlight definition map
 /// @see nvim_get_hl_by_id
-Dictionary nvim_get_hl_by_name(String name, Boolean rgb, Error *err)
+Dictionary nvim_get_hl_by_name(String name, Boolean rgb, Arena *arena, Error *err)
   FUNC_API_SINCE(3)
 {
   Dictionary result = ARRAY_DICT_INIT;
   int id = syn_name2id(name.data);
 
   if (id == 0) {
-    api_set_error(err, kErrorTypeException, "Invalid highlight name: %s",
-                  name.data);
+    api_set_error(err, kErrorTypeException, "Invalid highlight name: %s", name.data);
     return result;
   }
-  result = nvim_get_hl_by_id(id, rgb, err);
-  return result;
+  return nvim_get_hl_by_id(id, rgb, arena, err);
 }
 
 /// Gets a highlight definition by id. |hlID()|
@@ -100,17 +99,16 @@ Dictionary nvim_get_hl_by_name(String name, Boolean rgb, Error *err)
 /// @param[out] err Error details, if any
 /// @return Highlight definition map
 /// @see nvim_get_hl_by_name
-Dictionary nvim_get_hl_by_id(Integer hl_id, Boolean rgb, Error *err)
+Dictionary nvim_get_hl_by_id(Integer hl_id, Boolean rgb, Arena *arena, Error *err)
   FUNC_API_SINCE(3)
 {
   Dictionary dic = ARRAY_DICT_INIT;
   if (syn_get_final_id((int)hl_id) == 0) {
-    api_set_error(err, kErrorTypeException,
-                  "Invalid highlight id: %" PRId64, hl_id);
+    api_set_error(err, kErrorTypeException, "Invalid highlight id: %" PRId64, hl_id);
     return dic;
   }
   int attrcode = syn_id2attr((int)hl_id);
-  return hl_get_attr_by_id(attrcode, rgb, err);
+  return hl_get_attr_by_id(attrcode, rgb, arena, err);
 }
 
 /// Gets a highlight group by name
@@ -122,10 +120,10 @@ Integer nvim_get_hl_id_by_name(String name)
   return syn_check_group(name.data, name.size);
 }
 
-Dictionary nvim__get_hl_defs(Integer ns_id, Error *err)
+Dictionary nvim__get_hl_defs(Integer ns_id, Arena *arena, Error *err)
 {
   if (ns_id == 0) {
-    return get_global_hl_defs();
+    return get_global_hl_defs(arena);
   }
   abort();
 }
@@ -163,8 +161,8 @@ Dictionary nvim__get_hl_defs(Integer ns_id, Error *err)
 ///                - nocombine: boolean
 ///                - link: name of another highlight group to link to, see |:hi-link|.
 ///                - default: Don't override existing definition |:hi-default|
-///                - ctermfg: Sets foreground of cterm color |highlight-ctermfg|
-///                - ctermbg: Sets background of cterm color |highlight-ctermbg|
+///                - ctermfg: Sets foreground of cterm color |ctermfg|
+///                - ctermbg: Sets background of cterm color |ctermbg|
 ///                - cterm: cterm attribute map, like |highlight-args|. If not set,
 ///                         cterm attributes will match those from the attribute map
 ///                         documented above.
@@ -175,6 +173,10 @@ void nvim_set_hl(Integer ns_id, String name, Dict(highlight) *val, Error *err)
   FUNC_API_SINCE(7)
 {
   int hl_id = syn_check_group(name.data, name.size);
+  if (hl_id == 0) {
+    api_set_error(err, kErrorTypeException, "Invalid highlight name: %s", name.data);
+    return;
+  }
   int link_id = -1;
 
   HlAttrs attrs = dict2hlattrs(val, true, &link_id, err);
@@ -184,7 +186,7 @@ void nvim_set_hl(Integer ns_id, String name, Dict(highlight) *val, Error *err)
 }
 
 /// Set active namespace for highlights. This can be set for a single window,
-/// see |nvim_win_set_hl_ns|.
+/// see |nvim_win_set_hl_ns()|.
 ///
 /// @param ns_id the namespace to use
 /// @param[out] err Error details, if any
@@ -198,13 +200,13 @@ void nvim_set_hl_ns(Integer ns_id, Error *err)
 
   ns_hl_global = (NS)ns_id;
   hl_check_ns();
-  redraw_all_later(NOT_VALID);
+  redraw_all_later(UPD_NOT_VALID);
 }
 
 /// Set active namespace for highlights while redrawing.
 ///
 /// This function meant to be called while redrawing, primarily from
-/// |nvim_set_decoration_provider| on_win and on_line callbacks, which
+/// |nvim_set_decoration_provider()| on_win and on_line callbacks, which
 /// are allowed to change the namespace during a redraw cycle.
 ///
 /// @param ns_id the namespace to activate
@@ -227,14 +229,14 @@ void nvim_set_hl_ns_fast(Integer ns_id, Error *err)
 /// nvim_feedkeys().
 ///
 /// Example:
-/// <pre>
+/// <pre>vim
 ///     :let key = nvim_replace_termcodes("<C-o>", v:true, v:false, v:true)
 ///     :call nvim_feedkeys(key, 'n', v:false)
 /// </pre>
 ///
 /// @param keys         to be typed
 /// @param mode         behavior flags, see |feedkeys()|
-/// @param escape_ks    If true, escape K_SPECIAL bytes in `keys`
+/// @param escape_ks    If true, escape K_SPECIAL bytes in `keys`.
 ///                     This should be false if you already used
 ///                     |nvim_replace_termcodes()|, and true otherwise.
 /// @see feedkeys()
@@ -335,9 +337,9 @@ Integer nvim_input(String keys)
 ///       mouse input in a GUI. The deprecated pseudokey form
 ///       ("<LeftMouse><col,row>") of |nvim_input()| has the same limitation.
 ///
-/// @param button Mouse button: one of "left", "right", "middle", "wheel".
+/// @param button Mouse button: one of "left", "right", "middle", "wheel", "move".
 /// @param action For ordinary buttons, one of "press", "drag", "release".
-///               For the wheel, one of "up", "down", "left", "right".
+///               For the wheel, one of "up", "down", "left", "right". Ignored for "move".
 /// @param modifier String of modifiers each represented by a single char.
 ///                 The same specifiers are used as for a key press, except
 ///                 that the "-" separator is optional, so "C-A-", "c-a"
@@ -364,6 +366,8 @@ void nvim_input_mouse(String button, String action, String modifier, Integer gri
     code = KE_RIGHTMOUSE;
   } else if (strequal(button.data, "wheel")) {
     code = KE_MOUSEDOWN;
+  } else if (strequal(button.data, "move")) {
+    code = KE_MOUSEMOVE;
   } else {
     goto error;
   }
@@ -380,7 +384,7 @@ void nvim_input_mouse(String button, String action, String modifier, Integer gri
     } else {
       goto error;
     }
-  } else {
+  } else if (code != KE_MOUSEMOVE) {
     if (strequal(action.data, "press")) {
       // pass
     } else if (strequal(action.data, "drag")) {
@@ -520,7 +524,7 @@ Array nvim__runtime_inspect(void)
 
 /// Find files in runtime directories
 ///
-/// 'name' can contain wildcards. For example
+/// "name" can contain wildcards. For example
 /// nvim_get_runtime_file("colors/*.vim", true) will return all color
 /// scheme files. Always use forward slashes (/) in the search pattern for
 /// subdirectories regardless of platform.
@@ -722,8 +726,11 @@ void nvim_set_vvar(String name, Object value, Error *err)
 ///                text chunk with specified highlight. `hl_group` element
 ///                can be omitted for no highlight.
 /// @param history  if true, add to |message-history|.
-/// @param opts  Optional parameters. Reserved for future use.
-void nvim_echo(Array chunks, Boolean history, Dictionary opts, Error *err)
+/// @param opts  Optional parameters.
+///          - verbose: Message was printed as a result of 'verbose' option
+///            if Nvim was invoked with -V3log_file, the message will be
+///            redirected to the log_file and suppressed from direct output.
+void nvim_echo(Array chunks, Boolean history, Dict(echo_opts) *opts, Error *err)
   FUNC_API_SINCE(7)
 {
   HlMessage hl_msg = parse_hl_msg(chunks, err);
@@ -731,13 +738,19 @@ void nvim_echo(Array chunks, Boolean history, Dictionary opts, Error *err)
     goto error;
   }
 
-  if (opts.size > 0) {
-    api_set_error(err, kErrorTypeValidation, "opts dict isn't empty");
-    goto error;
+  bool verbose = api_object_to_bool(opts->verbose, "verbose", false, err);
+
+  if (verbose) {
+    verbose_enter();
   }
 
   msg_multiattr(hl_msg, history ? "echomsg" : "echo", history);
 
+  if (verbose) {
+    verbose_leave();
+    verbose_stop();  // flush now
+  }
+
   if (history) {
     // history takes ownership
     return;
@@ -961,7 +974,7 @@ fail:
 ///            mode. Note: keypresses are sent raw as they would be to the pty
 ///            master end. For instance, a carriage return is sent
 ///            as a "\r", not as a "\n". |textlock| applies. It is possible
-///            to call |nvim_chan_send| directly in the callback however.
+///            to call |nvim_chan_send()| directly in the callback however.
 ///                 ["input", term, bufnr, data]
 /// @param[out] err Error details, if any
 /// @return Channel id, or 0 on error
@@ -1009,7 +1022,7 @@ Integer nvim_open_term(Buffer buffer, DictionaryOf(LuaRef) opts, Error *err)
   return (Integer)chan->id;
 }
 
-static void term_write(char *buf, size_t size, void *data)
+static void term_write(char *buf, size_t size, void *data)  // NOLINT(readability-non-const-parameter)
 {
   Channel *chan = data;
   LuaRef cb = chan->stream.internal.cb;
@@ -1291,7 +1304,7 @@ void nvim_unsubscribe(uint64_t channel_id, String event)
 /// "#rrggbb" hexadecimal string.
 ///
 /// Example:
-/// <pre>
+/// <pre>vim
 ///     :echo nvim_get_color_by_name("Pink")
 ///     :echo nvim_get_color_by_name("#cbcbcb")
 /// </pre>
@@ -1419,10 +1432,10 @@ Dictionary nvim_get_mode(void)
 /// @param  mode       Mode short-name ("n", "i", "v", ...)
 /// @returns Array of |maparg()|-like dictionaries describing mappings.
 ///          The "buffer" key is always zero.
-ArrayOf(Dictionary) nvim_get_keymap(uint64_t channel_id, String mode)
+ArrayOf(Dictionary) nvim_get_keymap(String mode)
   FUNC_API_SINCE(3)
 {
-  return keymap_array(mode, NULL, channel_id == LUA_INTERNAL_CALL);
+  return keymap_array(mode, NULL);
 }
 
 /// Sets a global |mapping| for the given mode.
@@ -1433,12 +1446,12 @@ ArrayOf(Dictionary) nvim_get_keymap(uint64_t channel_id, String mode)
 /// Empty {rhs} is |<Nop>|. |keycodes| are replaced as usual.
 ///
 /// Example:
-/// <pre>
+/// <pre>vim
 ///     call nvim_set_keymap('n', ' <NL>', '', {'nowait': v:true})
 /// </pre>
 ///
 /// is equivalent to:
-/// <pre>
+/// <pre>vim
 ///     nmap <nowait> <Space><NL> <Nop>
 /// </pre>
 ///
@@ -1449,7 +1462,7 @@ ArrayOf(Dictionary) nvim_get_keymap(uint64_t channel_id, String mode)
 /// @param  rhs   Right-hand-side |{rhs}| of the mapping.
 /// @param  opts  Optional parameters map: keys are |:map-arguments|, values are booleans (default
 ///               false). Accepts all |:map-arguments| as keys excluding |<buffer>| but including
-///               |noremap| and "desc". Unknown key is an error.
+///               |:noremap| and "desc". Unknown key is an error.
 ///               "desc" can be used to give a description to the mapping.
 ///               When called from Lua, also accepts a "callback" key that takes a Lua function to
 ///               call when the mapping is executed.
@@ -1479,14 +1492,14 @@ void nvim_del_keymap(uint64_t channel_id, String mode, String lhs, Error *err)
 /// 1 is the |api-metadata| map (Dictionary).
 ///
 /// @returns 2-tuple [{channel-id}, {api-metadata}]
-Array nvim_get_api_info(uint64_t channel_id)
+Array nvim_get_api_info(uint64_t channel_id, Arena *arena)
   FUNC_API_SINCE(1) FUNC_API_FAST FUNC_API_REMOTE_ONLY
 {
-  Array rv = ARRAY_DICT_INIT;
+  Array rv = arena_array(arena, 2);
 
   assert(channel_id <= INT64_MAX);
-  ADD(rv, INTEGER_OBJ((int64_t)channel_id));
-  ADD(rv, DICTIONARY_OBJ(api_metadata()));
+  ADD_C(rv, INTEGER_OBJ((int64_t)channel_id));
+  ADD_C(rv, DICTIONARY_OBJ(api_metadata()));
 
   return rv;
 }
@@ -1545,9 +1558,9 @@ void nvim_set_client_info(uint64_t channel_id, String name, Dictionary version,
   FUNC_API_SINCE(4) FUNC_API_REMOTE_ONLY
 {
   Dictionary info = ARRAY_DICT_INIT;
-  PUT(info, "name", copy_object(STRING_OBJ(name)));
+  PUT(info, "name", copy_object(STRING_OBJ(name), NULL));
 
-  version = copy_dictionary(version);
+  version = copy_dictionary(version, NULL);
   bool has_major = false;
   for (size_t i = 0; i < version.size; i++) {
     if (strequal(version.items[i].key.data, "major")) {
@@ -1560,9 +1573,9 @@ void nvim_set_client_info(uint64_t channel_id, String name, Dictionary version,
   }
   PUT(info, "version", DICTIONARY_OBJ(version));
 
-  PUT(info, "type", copy_object(STRING_OBJ(type)));
-  PUT(info, "methods", DICTIONARY_OBJ(copy_dictionary(methods)));
-  PUT(info, "attributes", DICTIONARY_OBJ(copy_dictionary(attributes)));
+  PUT(info, "type", copy_object(STRING_OBJ(type), NULL));
+  PUT(info, "methods", DICTIONARY_OBJ(copy_dictionary(methods, NULL)));
+  PUT(info, "attributes", DICTIONARY_OBJ(copy_dictionary(attributes, NULL)));
 
   rpc_set_client_info(channel_id, info);
 }
@@ -1629,11 +1642,11 @@ Array nvim_list_chans(void)
 /// an error, it is a three-element array with the zero-based index of the call
 /// which resulted in an error, the error type and the error message. If an
 /// error occurred, the values from all preceding calls will still be returned.
-Array nvim_call_atomic(uint64_t channel_id, Array calls, Error *err)
+Array nvim_call_atomic(uint64_t channel_id, Array calls, Arena *arena, Error *err)
   FUNC_API_SINCE(1) FUNC_API_REMOTE_ONLY
 {
-  Array rv = ARRAY_DICT_INIT;
-  Array results = ARRAY_DICT_INIT;
+  Array rv = arena_array(arena, 2);
+  Array results = arena_array(arena, calls.size);
   Error nested_error = ERROR_INIT;
 
   size_t i;  // also used for freeing the variables
@@ -1642,21 +1655,21 @@ Array nvim_call_atomic(uint64_t channel_id, Array calls, Error *err)
       api_set_error(err,
                     kErrorTypeValidation,
                     "Items in calls array must be arrays");
-      goto validation_error;
+      goto theend;
     }
     Array call = calls.items[i].data.array;
     if (call.size != 2) {
       api_set_error(err,
                     kErrorTypeValidation,
                     "Items in calls array must be arrays of size 2");
-      goto validation_error;
+      goto theend;
     }
 
     if (call.items[0].type != kObjectTypeString) {
       api_set_error(err,
                     kErrorTypeValidation,
                     "Name must be String");
-      goto validation_error;
+      goto theend;
     }
     String name = call.items[0].data.string;
 
@@ -1664,7 +1677,7 @@ Array nvim_call_atomic(uint64_t channel_id, Array calls, Error *err)
       api_set_error(err,
                     kErrorTypeValidation,
                     "Args must be Array");
-      goto validation_error;
+      goto theend;
     }
     Array args = call.items[1].data.array;
 
@@ -1676,29 +1689,32 @@ Array nvim_call_atomic(uint64_t channel_id, Array calls, Error *err)
     if (ERROR_SET(&nested_error)) {
       break;
     }
-    Object result = handler.fn(channel_id, args, &nested_error);
+
+    Object result = handler.fn(channel_id, args, arena, &nested_error);
     if (ERROR_SET(&nested_error)) {
       // error handled after loop
       break;
     }
-
-    ADD(results, result);
+    // TODO(bfredl): wasteful copy. It could be avoided to encoding to msgpack
+    // directly here. But `result` might become invalid when next api function
+    // is called in the loop.
+    ADD_C(results, copy_object(result, arena));
+    if (!handler.arena_return) {
+      api_free_object(result);
+    }
   }
 
-  ADD(rv, ARRAY_OBJ(results));
+  ADD_C(rv, ARRAY_OBJ(results));
   if (ERROR_SET(&nested_error)) {
-    Array errval = ARRAY_DICT_INIT;
-    ADD(errval, INTEGER_OBJ((Integer)i));
-    ADD(errval, INTEGER_OBJ(nested_error.type));
-    ADD(errval, STRING_OBJ(cstr_to_string(nested_error.msg)));
-    ADD(rv, ARRAY_OBJ(errval));
+    Array errval = arena_array(arena, 3);
+    ADD_C(errval, INTEGER_OBJ((Integer)i));
+    ADD_C(errval, INTEGER_OBJ(nested_error.type));
+    ADD_C(errval, STRING_OBJ(copy_string(cstr_as_string(nested_error.msg), arena)));
+    ADD_C(rv, ARRAY_OBJ(errval));
   } else {
-    ADD(rv, NIL);
+    ADD_C(rv, NIL);
   }
-  goto theend;
 
-validation_error:
-  api_free_array(results);
 theend:
   api_clear_error(&nested_error);
   return rv;
@@ -1712,17 +1728,21 @@ theend:
 /// @param to_err   true: message is an error (uses `emsg` instead of `msg`)
 static void write_msg(String message, bool to_err)
 {
-  static size_t out_pos = 0, err_pos = 0;
-  static char out_line_buf[LINE_BUFFER_SIZE], err_line_buf[LINE_BUFFER_SIZE];
+  static StringBuilder out_line_buf = KV_INITIAL_VALUE;
+  static StringBuilder err_line_buf = KV_INITIAL_VALUE;
 
-#define PUSH_CHAR(i, pos, line_buf, msg) \
-  if (message.data[i] == NL || (pos) == LINE_BUFFER_SIZE - 1) { \
-    (line_buf)[pos] = NUL; \
-    msg(line_buf); \
-    (pos) = 0; \
+#define PUSH_CHAR(i, line_buf, msg) \
+  if (kv_max(line_buf) == 0) { \
+    kv_resize(line_buf, LINE_BUFFER_MIN_SIZE); \
+  } \
+  if (message.data[i] == NL) { \
+    kv_push(line_buf, NUL); \
+    msg(line_buf.items); \
+    kv_drop(line_buf, kv_size(line_buf)); \
+    kv_resize(line_buf, LINE_BUFFER_MIN_SIZE); \
     continue; \
   } \
-  (line_buf)[(pos)++] = message.data[i];
+  kv_push(line_buf, message.data[i]);
 
   no_wait_return++;
   for (uint32_t i = 0; i < message.size; i++) {
@@ -1730,9 +1750,9 @@ static void write_msg(String message, bool to_err)
       break;
     }
     if (to_err) {
-      PUSH_CHAR(i, err_pos, err_line_buf, emsg);
+      PUSH_CHAR(i, err_line_buf, emsg);
     } else {
-      PUSH_CHAR(i, out_pos, out_line_buf, msg);
+      PUSH_CHAR(i, out_line_buf, msg);
     }
   }
   no_wait_return--;
@@ -1751,7 +1771,7 @@ static void write_msg(String message, bool to_err)
 /// @return its argument.
 Object nvim__id(Object obj)
 {
-  return copy_object(obj);
+  return copy_object(obj, NULL);
 }
 
 /// Returns array given as argument.
@@ -1764,7 +1784,7 @@ Object nvim__id(Object obj)
 /// @return its argument.
 Array nvim__id_array(Array arr)
 {
-  return copy_object(ARRAY_OBJ(arr)).data.array;
+  return copy_array(arr, NULL);
 }
 
 /// Returns dictionary given as argument.
@@ -1777,7 +1797,7 @@ Array nvim__id_array(Array arr)
 /// @return its argument.
 Dictionary nvim__id_dictionary(Dictionary dct)
 {
-  return copy_object(DICTIONARY_OBJ(dct)).data.dictionary;
+  return copy_dictionary(dct, NULL);
 }
 
 /// Returns floating-point value given as argument.
@@ -1803,6 +1823,7 @@ Dictionary nvim__stats(void)
   PUT(rv, "log_skip", INTEGER_OBJ(g_stats.log_skip));
   PUT(rv, "lua_refcount", INTEGER_OBJ(nlua_get_global_ref_count()));
   PUT(rv, "redraw", INTEGER_OBJ(g_stats.redraw));
+  PUT(rv, "arena_alloc_count", INTEGER_OBJ((Integer)arena_alloc_count));
   return rv;
 }
 
@@ -1813,7 +1834,7 @@ Dictionary nvim__stats(void)
 ///   - "width"   Requested width of the UI
 ///   - "rgb"     true if the UI uses RGB colors (false implies |cterm-colors|)
 ///   - "ext_..." Requested UI extensions, see |ui-option|
-///   - "chan"    Channel id of remote UI (not present for TUI)
+///   - "chan"    |channel-id| of remote UI
 Array nvim_list_uis(void)
   FUNC_API_SINCE(4)
 {
@@ -1875,7 +1896,7 @@ Object nvim_get_proc(Integer pid, Error *err)
     api_set_error(err, kErrorTypeException, "Invalid pid: %" PRId64, pid);
     return NIL;
   }
-#ifdef WIN32
+#ifdef MSWIN
   rvobj.data.dictionary = os_proc_info((int)pid);
   if (rvobj.data.dictionary.size == 0) {  // Process not found.
     return NIL;
@@ -1897,19 +1918,20 @@ Object nvim_get_proc(Integer pid, Error *err)
   return rvobj;
 }
 
-/// Selects an item in the completion popupmenu.
+/// Selects an item in the completion popup menu.
 ///
-/// If |ins-completion| is not active this API call is silently ignored.
-/// Useful for an external UI using |ui-popupmenu| to control the popupmenu
-/// with the mouse. Can also be used in a mapping; use <cmd> |:map-cmd| to
-/// ensure the mapping doesn't end completion mode.
+/// If neither |ins-completion| nor |cmdline-completion| popup menu is active
+/// this API call is silently ignored.
+/// Useful for an external UI using |ui-popupmenu| to control the popup menu with the mouse.
+/// Can also be used in a mapping; use <Cmd> |:map-cmd| or a Lua mapping to ensure the mapping
+/// doesn't end completion mode.
 ///
-/// @param item   Index (zero-based) of the item to select. Value of -1 selects
-///               nothing and restores the original text.
-/// @param insert Whether the selection should be inserted in the buffer.
-/// @param finish Finish the completion and dismiss the popupmenu. Implies
-///               `insert`.
-/// @param  opts  Optional parameters. Reserved for future use.
+/// @param item    Index (zero-based) of the item to select. Value of -1 selects nothing
+///                and restores the original text.
+/// @param insert  For |ins-completion|, whether the selection should be inserted in the buffer.
+///                Ignored for |cmdline-completion|.
+/// @param finish  Finish the completion and dismiss the popup menu. Implies {insert}.
+/// @param opts    Optional parameters. Reserved for future use.
 /// @param[out] err Error details, if any
 void nvim_select_popupmenu_item(Integer item, Boolean insert, Boolean finish, Dictionary opts,
                                 Error *err)
@@ -1928,7 +1950,7 @@ void nvim_select_popupmenu_item(Integer item, Boolean insert, Boolean finish, Di
 }
 
 /// NB: if your UI doesn't use hlstate, this will not return hlstate first time
-Array nvim__inspect_cell(Integer grid, Integer row, Integer col, Error *err)
+Array nvim__inspect_cell(Integer grid, Integer row, Integer col, Arena *arena, Error *err)
 {
   Array ret = ARRAY_DICT_INIT;
 
@@ -1952,13 +1974,14 @@ Array nvim__inspect_cell(Integer grid, Integer row, Integer col, Error *err)
       || col < 0 || col >= g->cols) {
     return ret;
   }
+  ret = arena_array(arena, 3);
   size_t off = g->line_offset[(size_t)row] + (size_t)col;
-  ADD(ret, STRING_OBJ(cstr_to_string((char *)g->chars[off])));
+  ADD_C(ret, STRING_OBJ(cstr_as_string((char *)g->chars[off])));
   int attr = g->attrs[off];
-  ADD(ret, DICTIONARY_OBJ(hl_get_attr_by_id(attr, true, err)));
+  ADD_C(ret, DICTIONARY_OBJ(hl_get_attr_by_id(attr, true, arena, err)));
   // will not work first time
   if (!highlight_use_hlstate()) {
-    ADD(ret, ARRAY_OBJ(hl_inspect(attr)));
+    ADD_C(ret, ARRAY_OBJ(hl_inspect(attr)));
   }
   return ret;
 }
@@ -2040,7 +2063,7 @@ Array nvim_get_mark(String name, Dictionary opts, Error *err)
   // Marks are from an open buffer it fnum is non zero
   if (mark->fmark.fnum != 0) {
     bufnr = mark->fmark.fnum;
-    filename = (char *)buflist_nr2name(bufnr, true, true);
+    filename = buflist_nr2name(bufnr, true, true);
     allocated = true;
     // Marks comes from shada
   } else {
@@ -2088,7 +2111,7 @@ Array nvim_get_mark(String name, Dictionary opts, Error *err)
 ///                                'fillchars'). Treated as single-width even if it isn't.
 ///           - highlights: (boolean) Return highlight information.
 ///           - use_winbar: (boolean) Evaluate winbar instead of statusline.
-///           - use_tabline: (boolean) Evaluate tabline instead of statusline. When |TRUE|, {winid}
+///           - use_tabline: (boolean) Evaluate tabline instead of statusline. When true, {winid}
 ///                                    is ignored. Mutually exclusive with {use_winbar}.
 ///
 /// @param[out] err Error details, if any.
@@ -2096,7 +2119,7 @@ Array nvim_get_mark(String name, Dictionary opts, Error *err)
 ///       - str: (string) Characters that will be displayed on the statusline.
 ///       - width: (number) Display width of the statusline.
 ///       - highlights: Array containing highlight information of the statusline. Only included when
-///                     the "highlights" key in {opts} is |TRUE|. Each element of the array is a
+///                     the "highlights" key in {opts} is true. Each element of the array is a
 ///                     |Dictionary| with these keys:
 ///           - start: (number) Byte index (0-based) of first character that uses the highlight.
 ///           - group: (string) Name of highlight group.
@@ -2112,7 +2135,7 @@ Dictionary nvim_eval_statusline(String str, Dict(eval_statusline) *opts, Error *
   bool use_tabline = false;
   bool highlights = false;
 
-  if (str.size < 2 || memcmp(str.data, "%!", 2)) {
+  if (str.size < 2 || memcmp(str.data, "%!", 2) != 0) {
     const char *const errmsg = check_stl_option(str.data);
     if (errmsg) {
       api_set_error(err, kErrorTypeValidation, "%s", errmsg);
@@ -2210,10 +2233,12 @@ Dictionary nvim_eval_statusline(String str, Dict(eval_statusline) *opts, Error *
                                buf,
                                sizeof(buf),
                                str.data,
-                               false,
+                               NULL,
+                               0,
                                fillchar,
                                maxwidth,
                                hltab_ptr,
+                               NULL,
                                NULL);
 
   PUT(result, "width", INTEGER_OBJ(width));
@@ -2228,7 +2253,7 @@ Dictionary nvim_eval_statusline(String str, Dict(eval_statusline) *opts, Error *
 
     // If first character doesn't have a defined highlight,
     // add the default highlight at the beginning of the highlight list
-    if (hltab->start == NULL || ((char *)hltab->start - buf) != 0) {
+    if (hltab->start == NULL || (hltab->start - buf) != 0) {
       Dictionary hl_info = ARRAY_DICT_INIT;
       grpname = get_default_stl_hl(wp, use_winbar);
 
@@ -2246,7 +2271,7 @@ Dictionary nvim_eval_statusline(String str, Dict(eval_statusline) *opts, Error *
       if (sp->userhl == 0) {
         grpname = get_default_stl_hl(wp, use_winbar);
       } else if (sp->userhl < 0) {
-        grpname = (char *)syn_id2name(-sp->userhl);
+        grpname = syn_id2name(-sp->userhl);
       } else {
         snprintf(user_group, sizeof(user_group), "User%d", sp->userhl);
         grpname = user_group;
diff --git a/src/nvim/api/vimscript.c b/src/nvim/api/vimscript.c
index a28bfd2ab9..af1b23b712 100644
--- a/src/nvim/api/vimscript.c
+++ b/src/nvim/api/vimscript.c
@@ -2,26 +2,31 @@
 // it. PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
 
 #include <assert.h>
-#include <limits.h>
-#include <stdlib.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <string.h>
 
+#include "klib/kvec.h"
 #include "nvim/api/private/converter.h"
 #include "nvim/api/private/defs.h"
 #include "nvim/api/private/helpers.h"
 #include "nvim/api/vimscript.h"
 #include "nvim/ascii.h"
-#include "nvim/autocmd.h"
+#include "nvim/buffer_defs.h"
 #include "nvim/eval.h"
 #include "nvim/eval/typval.h"
+#include "nvim/eval/typval_defs.h"
 #include "nvim/eval/userfunc.h"
 #include "nvim/ex_docmd.h"
-#include "nvim/ops.h"
+#include "nvim/garray.h"
+#include "nvim/globals.h"
+#include "nvim/memory.h"
+#include "nvim/pos.h"
 #include "nvim/runtime.h"
-#include "nvim/strings.h"
 #include "nvim/vim.h"
 #include "nvim/viml/parser/expressions.h"
 #include "nvim/viml/parser/parser.h"
-#include "nvim/window.h"
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "api/vimscript.c.generated.h"
@@ -137,7 +142,7 @@ Object nvim_eval(String expr, Error *err)
     if (!recursive) {
       force_abort = false;
       suppress_errthrow = false;
-      current_exception = NULL;
+      did_throw = false;
       // `did_emsg` is set by emsg(), which cancels execution.
       did_emsg = false;
     }
@@ -196,7 +201,7 @@ static Object _call_function(String fn, Array args, dict_T *self, Error *err)
     if (!recursive) {
       force_abort = false;
       suppress_errthrow = false;
-      current_exception = NULL;
+      did_throw = false;
       // `did_emsg` is set by emsg(), which cancels execution.
       did_emsg = false;
     }
@@ -204,10 +209,10 @@ static Object _call_function(String fn, Array args, dict_T *self, Error *err)
     try_start();
     typval_T rettv;
     funcexe_T funcexe = FUNCEXE_INIT;
-    funcexe.firstline = curwin->w_cursor.lnum;
-    funcexe.lastline = curwin->w_cursor.lnum;
-    funcexe.evaluate = true;
-    funcexe.selfdict = self;
+    funcexe.fe_firstline = curwin->w_cursor.lnum;
+    funcexe.fe_lastline = curwin->w_cursor.lnum;
+    funcexe.fe_evaluate = true;
+    funcexe.fe_selfdict = self;
     // call_func() retval is deceptive, ignore it.  Instead we set `msg_list`
     // (see above) to capture abort-causing non-exception errors.
     (void)call_func(fn.data, (int)fn.size, &rettv, (int)args.size,
@@ -304,7 +309,7 @@ Object nvim_call_dict_function(Object dict, String fn, Array args, Error *err)
     }
     fn = (String) {
       .data = di->di_tv.vval.v_string,
-      .size = STRLEN(di->di_tv.vval.v_string),
+      .size = strlen(di->di_tv.vval.v_string),
     };
   }
 
@@ -532,7 +537,7 @@ Dictionary nvim_parse_expression(String expr, String flags, Boolean highlight, E
       kv_drop(ast_conv_stack, 1);
     } else {
       if (cur_item.ret_node_p->type == kObjectTypeNil) {
-        size_t items_size = (size_t)(3  // "type", "start" and "len"
+        size_t items_size = (size_t)(3  // "type", "start" and "len"  // NOLINT(bugprone-misplaced-widening-cast)
                                      + (node->children != NULL)  // "children"
                                      + (node->type == kExprNodeOption
                                         || node->type == kExprNodePlainIdentifier)  // "scope"
diff --git a/src/nvim/api/win_config.c b/src/nvim/api/win_config.c
index 6c37df6af8..0ffeac1bff 100644
--- a/src/nvim/api/win_config.c
+++ b/src/nvim/api/win_config.c
@@ -1,19 +1,27 @@
 // This is an open source non-commercial project. Dear PVS-Studio, please check
 // it. PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
 
-#include <assert.h>
 #include <stdbool.h>
-#include <stddef.h>
-#include <stdint.h>
+#include <string.h>
 
+#include "klib/kvec.h"
+#include "nvim/api/extmark.h"
 #include "nvim/api/private/defs.h"
 #include "nvim/api/private/helpers.h"
 #include "nvim/api/win_config.h"
 #include "nvim/ascii.h"
+#include "nvim/buffer_defs.h"
+#include "nvim/decoration.h"
 #include "nvim/drawscreen.h"
+#include "nvim/extmark_defs.h"
+#include "nvim/globals.h"
+#include "nvim/grid_defs.h"
 #include "nvim/highlight_group.h"
+#include "nvim/macros.h"
+#include "nvim/mbyte.h"
+#include "nvim/memory.h"
 #include "nvim/option.h"
-#include "nvim/strings.h"
+#include "nvim/pos.h"
 #include "nvim/syntax.h"
 #include "nvim/ui.h"
 #include "nvim/window.h"
@@ -47,13 +55,13 @@
 /// this should not be used to specify arbitrary WM screen positions.
 ///
 /// Example (Lua): window-relative float
-/// <pre>
+/// <pre>lua
 ///     vim.api.nvim_open_win(0, false,
 ///       {relative='win', row=3, col=3, width=12, height=3})
 /// </pre>
 ///
 /// Example (Lua): buffer-relative float (travels as buffer is scrolled)
-/// <pre>
+/// <pre>lua
 ///     vim.api.nvim_open_win(0, false,
 ///       {relative='win', width=12, height=3, bufpos={100,10}})
 /// </pre>
@@ -66,6 +74,7 @@
 ///      - "editor" The global editor grid
 ///      - "win"    Window given by the `win` field, or current window.
 ///      - "cursor" Cursor position in current window.
+///      - "mouse"  Mouse position
 ///   - win: |window-ID| for relative="win".
 ///   - anchor: Decides which corner of the float to place at (row,col):
 ///      - "NW" northwest (default)
@@ -106,10 +115,11 @@
 ///                    float where the text should not be edited. Disables
 ///                    'number', 'relativenumber', 'cursorline', 'cursorcolumn',
 ///                    'foldcolumn', 'spell' and 'list' options. 'signcolumn'
-///                    is changed to `auto` and 'colorcolumn' is cleared. The
-///                    end-of-buffer region is hidden by setting `eob` flag of
+///                    is changed to `auto` and 'colorcolumn' is cleared.
+///                    'statuscolumn' is changed to empty. The end-of-buffer
+///                     region is hidden by setting `eob` flag of
 ///                    'fillchars' to a space char, and clearing the
-///                    |EndOfBuffer| region in 'winhighlight'.
+///                    |hl-EndOfBuffer| region in 'winhighlight'.
 ///   - border: Style of (optional) window border. This can either be a string
 ///      or an array. The string values are
 ///     - "none": No border (default).
@@ -133,7 +143,12 @@
 ///     will only make vertical borders but not horizontal ones.
 ///     By default, `FloatBorder` highlight is used, which links to `WinSeparator`
 ///     when not defined.  It could also be specified by character:
-///       [ {"+", "MyCorner"}, {"x", "MyBorder"} ].
+///       [ ["+", "MyCorner"], ["x", "MyBorder"] ].
+///   - title: Title (optional) in window border, String or list.
+///     List is [text, highlight] tuples. if is string the default
+///     highlight group is `FloatTitle`.
+///   - title_pos: Title position must set with title option.
+///     value can be of `left` `center` `right` default is left.
 ///   - noautocmd: If true then no buffer-related autocommand events such as
 ///                  |BufEnter|, |BufLeave| or |BufWinEnter| may fire from
 ///                  calling this function.
@@ -202,7 +217,7 @@ void nvim_win_set_config(Window window, Dict(float_config) *config, Error *err)
     if (!win_new_float(win, false, fconfig, err)) {
       return;
     }
-    redraw_later(win, NOT_VALID);
+    redraw_later(win, UPD_NOT_VALID);
   } else {
     win_config_float(win, fconfig);
     win->w_pos_changed = true;
@@ -263,7 +278,7 @@ Dictionary nvim_win_get_config(Window window, Error *err)
         String s = cstrn_to_string((const char *)config->border_chars[i], sizeof(schar_T));
 
         int hi_id = config->border_hl_ids[i];
-        char *hi_name = (char *)syn_id2name(hi_id);
+        char *hi_name = syn_id2name(hi_id);
         if (hi_name[0]) {
           ADD(tuple, STRING_OBJ(s));
           ADD(tuple, STRING_OBJ(cstr_to_string((const char *)hi_name)));
@@ -273,6 +288,29 @@ Dictionary nvim_win_get_config(Window window, Error *err)
         }
       }
       PUT(rv, "border", ARRAY_OBJ(border));
+      if (config->title) {
+        Array titles = ARRAY_DICT_INIT;
+        VirtText title_datas = config->title_chunks;
+        for (size_t i = 0; i < title_datas.size; i++) {
+          Array tuple = ARRAY_DICT_INIT;
+          ADD(tuple, CSTR_TO_OBJ((const char *)title_datas.items[i].text));
+          if (title_datas.items[i].hl_id > 0) {
+            ADD(tuple,
+                STRING_OBJ(cstr_to_string((const char *)syn_id2name(title_datas.items[i].hl_id))));
+          }
+          ADD(titles, ARRAY_OBJ(tuple));
+        }
+        PUT(rv, "title", ARRAY_OBJ(titles));
+        char *title_pos;
+        if (config->title_pos == kAlignLeft) {
+          title_pos = "left";
+        } else if (config->title_pos == kAlignCenter) {
+          title_pos = "center";
+        } else {
+          title_pos = "right";
+        }
+        PUT(rv, "title_pos", CSTR_TO_OBJ(title_pos));
+      }
     }
   }
 
@@ -312,6 +350,8 @@ static bool parse_float_relative(String relative, FloatRelative *out)
     *out = kFloatRelativeWindow;
   } else if (striequal(str, "cursor")) {
     *out = kFloatRelativeCursor;
+  } else if (striequal(str, "mouse")) {
+    *out = kFloatRelativeMouse;
   } else {
     return false;
   }
@@ -330,7 +370,74 @@ static bool parse_float_bufpos(Array bufpos, lpos_T *out)
   return true;
 }
 
-static void parse_border_style(Object style, FloatConfig *fconfig, Error *err)
+static void parse_border_title(Object title, Object title_pos, FloatConfig *fconfig, Error *err)
+{
+  if (!parse_title_pos(title_pos, fconfig, err)) {
+    return;
+  }
+
+  if (title.type == kObjectTypeString) {
+    if (title.data.string.size == 0) {
+      fconfig->title = false;
+      return;
+    }
+    int hl_id = syn_check_group(S_LEN("FloatTitle"));
+    kv_push(fconfig->title_chunks, ((VirtTextChunk){ .text = xstrdup(title.data.string.data),
+                                                     .hl_id = hl_id }));
+    fconfig->title_width = (int)mb_string2cells(title.data.string.data);
+    fconfig->title = true;
+    return;
+  }
+
+  if (title.type != kObjectTypeArray) {
+    api_set_error(err, kErrorTypeValidation, "title must be string or array");
+    return;
+  }
+
+  if (title.data.array.size == 0) {
+    api_set_error(err, kErrorTypeValidation, "title cannot be an empty array");
+    return;
+  }
+
+  fconfig->title_width = 0;
+  fconfig->title_chunks = parse_virt_text(title.data.array, err, &fconfig->title_width);
+
+  fconfig->title = true;
+}
+
+static bool parse_title_pos(Object title_pos, FloatConfig *fconfig, Error *err)
+{
+  if (!HAS_KEY(title_pos)) {
+    fconfig->title_pos = kAlignLeft;
+    return true;
+  }
+
+  if (title_pos.type != kObjectTypeString) {
+    api_set_error(err, kErrorTypeValidation, "title_pos must be string");
+    return false;
+  }
+
+  if (title_pos.data.string.size == 0) {
+    fconfig->title_pos = kAlignLeft;
+    return true;
+  }
+
+  char *pos = title_pos.data.string.data;
+
+  if (strequal(pos, "left")) {
+    fconfig->title_pos = kAlignLeft;
+  } else if (strequal(pos, "center")) {
+    fconfig->title_pos = kAlignCenter;
+  } else if (strequal(pos, "right")) {
+    fconfig->title_pos = kAlignRight;
+  } else {
+    api_set_error(err, kErrorTypeValidation, "invalid title_pos value");
+    return false;
+  }
+  return true;
+}
+
+static void parse_border_style(Object style,  FloatConfig *fconfig, Error *err)
 {
   struct {
     const char *name;
@@ -414,6 +521,8 @@ static void parse_border_style(Object style, FloatConfig *fconfig, Error *err)
     String str = style.data.string;
     if (str.size == 0 || strequal(str.data, "none")) {
       fconfig->border = false;
+      // title does not work with border equal none
+      fconfig->title = false;
       return;
     }
     for (size_t i = 0; defaults[i].name; i++) {
@@ -603,6 +712,29 @@ static bool parse_float_config(Dict(float_config) *config, FloatConfig *fconfig,
     return false;
   }
 
+  if (HAS_KEY(config->title_pos)) {
+    if (!HAS_KEY(config->title)) {
+      api_set_error(err, kErrorTypeException, "title_pos requires title to be set");
+      return false;
+    }
+  }
+
+  if (HAS_KEY(config->title)) {
+    // title only work with border
+    if (!HAS_KEY(config->border) && !fconfig->border) {
+      api_set_error(err, kErrorTypeException, "title requires border to be set");
+      return false;
+    }
+
+    if (fconfig->title) {
+      clear_virttext(&fconfig->title_chunks);
+    }
+    parse_border_title(config->title, config->title_pos, fconfig, err);
+    if (ERROR_SET(err)) {
+      return false;
+    }
+  }
+
   if (HAS_KEY(config->border)) {
     parse_border_style(config->border, fconfig, err);
     if (ERROR_SET(err)) {
diff --git a/src/nvim/api/window.c b/src/nvim/api/window.c
index 580dfd8639..e2c234ab29 100644
--- a/src/nvim/api/window.c
+++ b/src/nvim/api/window.c
@@ -10,16 +10,18 @@
 #include "nvim/api/private/helpers.h"
 #include "nvim/api/window.h"
 #include "nvim/ascii.h"
-#include "nvim/buffer.h"
+#include "nvim/buffer_defs.h"
 #include "nvim/cursor.h"
 #include "nvim/drawscreen.h"
+#include "nvim/eval/window.h"
 #include "nvim/ex_docmd.h"
+#include "nvim/gettext.h"
 #include "nvim/globals.h"
 #include "nvim/lua/executor.h"
+#include "nvim/memline_defs.h"
 #include "nvim/move.h"
-#include "nvim/option.h"
-#include "nvim/syntax.h"
-#include "nvim/vim.h"
+#include "nvim/pos.h"
+#include "nvim/types.h"
 #include "nvim/window.h"
 
 /// Gets the current buffer in a window
@@ -51,7 +53,9 @@ void nvim_win_set_buf(Window window, Buffer buffer, Error *err)
   win_set_buf(window, buffer, false, err);
 }
 
-/// Gets the (1,0)-indexed cursor position in the window. |api-indexing|
+/// Gets the (1,0)-indexed, buffer-relative cursor position for a given window
+/// (different windows showing the same buffer have independent cursor
+/// positions). |api-indexing|
 ///
 /// @param window   Window handle, or 0 for current window
 /// @param[out] err Error details, if any
@@ -115,10 +119,15 @@ void nvim_win_set_cursor(Window window, ArrayOf(Integer, 2) pos, Error *err)
   // Make sure we stick in this column.
   win->w_set_curswant = true;
 
-  // make sure cursor is in visible range even if win != curwin
-  update_topline_win(win);
+  // make sure cursor is in visible range and
+  // cursorcolumn and cursorline are updated even if win != curwin
+  switchwin_T switchwin;
+  switch_win(&switchwin, win, NULL, true);
+  update_topline(curwin);
+  validate_cursor();
+  restore_win(&switchwin, true);
 
-  redraw_later(win, VALID);
+  redraw_later(win, UPD_VALID);
   win->w_redr_status = true;
 }
 
@@ -160,9 +169,11 @@ void nvim_win_set_height(Window window, Integer height, Error *err)
 
   win_T *savewin = curwin;
   curwin = win;
+  curbuf = curwin->w_buffer;
   try_start();
   win_setheight((int)height);
   curwin = savewin;
+  curbuf = curwin->w_buffer;
   try_end(err);
 }
 
@@ -205,9 +216,11 @@ void nvim_win_set_width(Window window, Integer width, Error *err)
 
   win_T *savewin = curwin;
   curwin = win;
+  curbuf = curwin->w_buffer;
   try_start();
   win_setwidth((int)width);
   curwin = savewin;
+  curbuf = curwin->w_buffer;
   try_end(err);
 }
 
@@ -340,7 +353,7 @@ Boolean nvim_win_is_valid(Window window)
 ///
 /// Like |:hide| the buffer becomes hidden unless another window is editing it,
 /// or 'bufhidden' is `unload`, `delete` or `wipe` as opposed to |:close| or
-/// |nvim_win_close|, which will close the buffer.
+/// |nvim_win_close()|, which will close the buffer.
 ///
 /// @param window   Window handle, or 0 for current window
 /// @param[out] err Error details, if any
@@ -356,11 +369,16 @@ void nvim_win_hide(Window window, Error *err)
   tabpage_T *tabpage = win_find_tabpage(win);
   TryState tstate;
   try_enter(&tstate);
-  if (tabpage == curtab) {
+
+  // Never close the autocommand window.
+  if (is_aucmd_win(win)) {
+    emsg(_(e_autocmd_close));
+  } else if (tabpage == curtab) {
     win_close(win, false, false);
   } else {
     win_close_othertab(win, false, tabpage);
   }
+
   vim_ignored = try_leave(&tstate, err);
 }
 
@@ -430,7 +448,7 @@ Object nvim_win_call(Window window, LuaRef fun, Error *err)
 /// Set highlight namespace for a window. This will use highlights defined in
 /// this namespace, but fall back to global highlights (ns=0) when missing.
 ///
-/// This takes predecence over the 'winhighlight' option.
+/// This takes precedence over the 'winhighlight' option.
 ///
 /// @param ns_id the namespace to use
 /// @param[out] err Error details, if any
@@ -449,5 +467,5 @@ void nvim_win_set_hl_ns(Window window, Integer ns_id, Error *err)
 
   win->w_ns_hl = (NS)ns_id;
   win->w_hl_needs_update = true;
-  redraw_later(win, NOT_VALID);
+  redraw_later(win, UPD_NOT_VALID);
 }