Merge remote-tracking branch 'upstream/master' into mix_20240309

13 files changed, 704 insertions, 387 deletions

diff --git a/src/nvim/api/autocmd.c b/src/nvim/api/autocmd.c
index d71bcc4bcf..ca8367b7ce 100644
--- a/src/nvim/api/autocmd.c
+++ b/src/nvim/api/autocmd.c
@@ -381,15 +381,15 @@ cleanup:
 ///             - 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 a truthy
-///             value (not `false` or `nil`) to delete the autocommand. Receives a table argument
-///             with these keys:
+///             value (not `false` or `nil`) to delete the autocommand. Receives one argument,
+///             a table with these keys: [event-args]()
 ///                 - 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 from [nvim_exec_autocmds()]
+///                 - data: (any) arbitrary data passed from [nvim_exec_autocmds()] [event-data]()
 ///             - command (string) optional: Vim command to execute on event. Cannot be used with
 ///             {callback}
 ///             - once (boolean) optional: defaults to false. Run the autocommand
diff --git a/src/nvim/api/buffer.c b/src/nvim/api/buffer.c
index 7f195de959..7e64808709 100644
--- a/src/nvim/api/buffer.c
+++ b/src/nvim/api/buffer.c
@@ -39,6 +39,7 @@
 #include "nvim/memory_defs.h"
 #include "nvim/move.h"
 #include "nvim/ops.h"
+#include "nvim/option_vars.h"
 #include "nvim/pos_defs.h"
 #include "nvim/state_defs.h"
 #include "nvim/types_defs.h"
@@ -229,20 +230,6 @@ Boolean nvim_buf_detach(uint64_t channel_id, Buffer buffer, Error *err)
   return true;
 }
 
-/// @nodoc
-void nvim__buf_redraw_range(Buffer buffer, Integer first, Integer last, Error *err)
-{
-  buf_T *buf = find_buffer_by_handle(buffer, err);
-  if (!buf) {
-    return;
-  }
-  if (last < 0) {
-    last = buf->b_ml.ml_line_count;
-  }
-
-  redraw_buf_range_later(buf, (linenr_T)first + 1, (linenr_T)last);
-}
-
 /// Gets a line-range from the buffer.
 ///
 /// Indexing is zero-based, end-exclusive. Negative indices are interpreted
@@ -529,18 +516,18 @@ void nvim_buf_set_text(uint64_t channel_id, Buffer buffer, Integer start_row, In
 
   // Another call to ml_get_buf() may free the lines, so we make copies
   char *str_at_start = ml_get_buf(buf, (linenr_T)start_row);
-  size_t len_at_start = strlen(str_at_start);
-  str_at_start = arena_memdupz(arena, str_at_start, len_at_start);
-  start_col = start_col < 0 ? (int64_t)len_at_start + start_col + 1 : start_col;
-  VALIDATE_RANGE((start_col >= 0 && (size_t)start_col <= len_at_start), "start_col", {
+  colnr_T len_at_start = ml_get_buf_len(buf, (linenr_T)start_row);
+  str_at_start = arena_memdupz(arena, str_at_start, (size_t)len_at_start);
+  start_col = start_col < 0 ? len_at_start + start_col + 1 : start_col;
+  VALIDATE_RANGE((start_col >= 0 && start_col <= len_at_start), "start_col", {
     return;
   });
 
   char *str_at_end = ml_get_buf(buf, (linenr_T)end_row);
-  size_t len_at_end = strlen(str_at_end);
-  str_at_end = arena_memdupz(arena, str_at_end, len_at_end);
-  end_col = end_col < 0 ? (int64_t)len_at_end + end_col + 1 : end_col;
-  VALIDATE_RANGE((end_col >= 0 && (size_t)end_col <= len_at_end), "end_col", {
+  colnr_T len_at_end = ml_get_buf_len(buf, (linenr_T)end_row);
+  str_at_end = arena_memdupz(arena, str_at_end, (size_t)len_at_end);
+  end_col = end_col < 0 ? len_at_end + end_col + 1 : end_col;
+  VALIDATE_RANGE((end_col >= 0 && end_col <= len_at_end), "end_col", {
     return;
   });
 
@@ -563,12 +550,10 @@ void nvim_buf_set_text(uint64_t channel_id, Buffer buffer, Integer start_row, In
   if (start_row == end_row) {
     old_byte = (bcount_t)end_col - start_col;
   } else {
-    old_byte += (bcount_t)len_at_start - start_col;
+    old_byte += len_at_start - start_col;
     for (int64_t i = 1; i < end_row - start_row; i++) {
       int64_t lnum = start_row + i;
-
-      const char *bufline = ml_get_buf(buf, (linenr_T)lnum);
-      old_byte += (bcount_t)(strlen(bufline)) + 1;
+      old_byte += ml_get_buf_len(buf, (linenr_T)lnum) + 1;
     }
     old_byte += (bcount_t)end_col + 1;
   }
@@ -577,7 +562,7 @@ void nvim_buf_set_text(uint64_t channel_id, Buffer buffer, Integer start_row, In
   String last_item = replacement.items[replacement.size - 1].data.string;
 
   size_t firstlen = (size_t)start_col + first_item.size;
-  size_t last_part_len = len_at_end - (size_t)end_col;
+  size_t last_part_len = (size_t)len_at_end - (size_t)end_col;
   if (replacement.size == 1) {
     firstlen += last_part_len;
   }
@@ -970,7 +955,7 @@ String nvim_buf_get_name(Buffer buffer, Error *err)
   return cstr_as_string(buf->b_ffname);
 }
 
-/// Sets the full file name for a buffer
+/// Sets the full file name for a buffer, like |:file_f|
 ///
 /// @param buffer     Buffer handle, or 0 for current buffer
 /// @param name       Buffer name
@@ -986,12 +971,23 @@ void nvim_buf_set_name(Buffer buffer, String name, Error *err)
 
   try_start();
 
+  const bool is_curbuf = buf == curbuf;
+  const int save_acd = p_acd;
+  if (!is_curbuf) {
+    // Temporarily disable 'autochdir' when setting file name for another buffer.
+    p_acd = false;
+  }
+
   // Using aucmd_*: autocommands will be executed by rename_buffer
   aco_save_T aco;
   aucmd_prepbuf(&aco, buf);
   int ren_ret = rename_buffer(name.data);
   aucmd_restbuf(&aco);
 
+  if (!is_curbuf) {
+    p_acd = save_acd;
+  }
+
   if (try_end(err)) {
     return;
   }
@@ -1271,10 +1267,13 @@ static void fix_cursor(win_T *win, linenr_T lo, linenr_T hi, linenr_T extra)
     } else if (extra < 0) {
       check_cursor_lnum(win);
     }
-    check_cursor_col_win(win);
+    check_cursor_col(win);
     changed_cline_bef_curs(win);
+    win->w_valid &= ~(VALID_BOTLINE_AP);
+    update_topline(win);
+  } else {
+    invalidate_botline(win);
   }
-  invalidate_botline(win);
 }
 
 /// Fix cursor position after replacing text
@@ -1309,7 +1308,7 @@ static void fix_cursor_cols(win_T *win, linenr_T start_row, colnr_T start_col, l
 
     // it's easier to work with a single value here.
     // col and coladd are fixed by a later call
-    // to check_cursor_col_win when necessary
+    // to check_cursor_col when necessary
     win->w_cursor.col += win->w_cursor.coladd;
     win->w_cursor.coladd = 0;
 
@@ -1324,7 +1323,7 @@ static void fix_cursor_cols(win_T *win, linenr_T start_row, colnr_T start_col, l
       // it already (in case virtualedit is active)
       // column might be additionally adjusted below
       // to keep it inside col range if needed
-      colnr_T len = (colnr_T)strlen(ml_get_buf(win->w_buffer, new_end_row));
+      colnr_T len = ml_get_buf_len(win->w_buffer, new_end_row);
       if (win->w_cursor.col < len) {
         win->w_cursor.col = len;
       }
@@ -1345,7 +1344,7 @@ static void fix_cursor_cols(win_T *win, linenr_T start_row, colnr_T start_col, l
     }
   }
 
-  check_cursor_col_win(win);
+  check_cursor_col(win);
   changed_cline_bef_curs(win);
   invalidate_botline(win);
 }
@@ -1424,6 +1423,7 @@ void buf_collect_lines(buf_T *buf, size_t n, linenr_T start, int start_idx, bool
   for (size_t i = 0; i < n; i++) {
     linenr_T lnum = start + (linenr_T)i;
     char *bufstr = ml_get_buf(buf, lnum);
-    push_linestr(lstate, l, bufstr, strlen(bufstr), start_idx + (int)i, replace_nl, arena);
+    size_t bufstrlen = (size_t)ml_get_buf_len(buf, lnum);
+    push_linestr(lstate, l, bufstr, bufstrlen, start_idx + (int)i, replace_nl, arena);
   }
 }
diff --git a/src/nvim/api/deprecated.c b/src/nvim/api/deprecated.c
index 6254e9fbd8..af3bfe2c03 100644
--- a/src/nvim/api/deprecated.c
+++ b/src/nvim/api/deprecated.c
@@ -20,6 +20,9 @@
 #include "nvim/lua/executor.h"
 #include "nvim/memory.h"
 #include "nvim/memory_defs.h"
+#include "nvim/msgpack_rpc/channel.h"
+#include "nvim/msgpack_rpc/channel_defs.h"
+#include "nvim/msgpack_rpc/unpacker.h"
 #include "nvim/option.h"
 #include "nvim/option_defs.h"
 #include "nvim/pos_defs.h"
@@ -697,3 +700,109 @@ static void set_option_to(uint64_t channel_id, void *to, OptReqScope req_scope,
     set_option_value_for(name.data, opt_idx, optval, opt_flags, req_scope, to, err);
   });
 }
+
+/// @deprecated Use nvim_exec_lua() instead.
+///
+/// Calls many API methods atomically.
+///
+/// This has two main usages:
+/// 1. To perform several requests from an async context atomically, i.e.
+///    without interleaving redraws, RPC requests from other clients, or user
+///    interactions (however API methods may trigger autocommands or event
+///    processing which have such side effects, e.g. |:sleep| may wake timers).
+/// 2. To minimize RPC overhead (roundtrips) of a sequence of many requests.
+///
+/// @param channel_id
+/// @param calls an array of calls, where each call is described by an array
+///              with two elements: the request name, and an array of arguments.
+/// @param[out] err Validation error details (malformed `calls` parameter),
+///             if any. Errors from batched calls are given in the return value.
+///
+/// @return Array of two elements. The first is an array of return
+/// values. The second is NIL if all calls succeeded. If a call resulted in
+/// 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, Arena *arena, Error *err)
+  FUNC_API_SINCE(1) FUNC_API_DEPRECATED_SINCE(12) FUNC_API_REMOTE_ONLY
+{
+  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
+  for (i = 0; i < calls.size; i++) {
+    VALIDATE_T("'calls' item", kObjectTypeArray, calls.items[i].type, {
+      goto theend;
+    });
+    Array call = calls.items[i].data.array;
+    VALIDATE_EXP((call.size == 2), "'calls' item", "2-item Array", NULL, {
+      goto theend;
+    });
+    VALIDATE_T("name", kObjectTypeString, call.items[0].type, {
+      goto theend;
+    });
+    String name = call.items[0].data.string;
+    VALIDATE_T("call args", kObjectTypeArray, call.items[1].type, {
+      goto theend;
+    });
+    Array args = call.items[1].data.array;
+
+    MsgpackRpcRequestHandler handler =
+      msgpack_rpc_get_handler_for(name.data,
+                                  name.size,
+                                  &nested_error);
+
+    if (ERROR_SET(&nested_error)) {
+      break;
+    }
+
+    Object result = handler.fn(channel_id, args, arena, &nested_error);
+    if (ERROR_SET(&nested_error)) {
+      // error handled after loop
+      break;
+    }
+    // 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.ret_alloc) {
+      api_free_object(result);
+    }
+  }
+
+  ADD_C(rv, ARRAY_OBJ(results));
+  if (ERROR_SET(&nested_error)) {
+    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_C(rv, NIL);
+  }
+
+theend:
+  api_clear_error(&nested_error);
+  return rv;
+}
+
+/// @deprecated
+///
+/// @param channel_id Channel id (passed automatically by the dispatcher)
+/// @param event      Event type string
+void nvim_subscribe(uint64_t channel_id, String event)
+  FUNC_API_SINCE(1) FUNC_API_REMOTE_ONLY
+{
+  // Does nothing. `rpcnotify(0,…)` broadcasts to all channels, there are no "subscriptions".
+}
+
+/// @deprecated
+///
+/// @param channel_id Channel id (passed automatically by the dispatcher)
+/// @param event      Event type string
+void nvim_unsubscribe(uint64_t channel_id, String event)
+  FUNC_API_SINCE(1) FUNC_API_REMOTE_ONLY
+{
+  // Does nothing. `rpcnotify(0,…)` broadcasts to all channels, there are no "subscriptions".
+}
diff --git a/src/nvim/api/extmark.c b/src/nvim/api/extmark.c
index 1b03a97edb..85cce45560 100644
--- a/src/nvim/api/extmark.c
+++ b/src/nvim/api/extmark.c
@@ -121,7 +121,7 @@ Array virt_text_to_array(VirtText vt, bool hl_name, Arena *arena)
     Array hl_array = arena_array(arena, i < j ? j - i + 1 : 0);
     for (; i < j; i++) {
       int hl_id = kv_A(vt, i).hl_id;
-      if (hl_id > 0) {
+      if (hl_id >= 0) {
         ADD_C(hl_array, hl_group_name(hl_id, hl_name));
       }
     }
@@ -131,11 +131,11 @@ Array virt_text_to_array(VirtText vt, bool hl_name, Arena *arena)
     Array chunk = arena_array(arena, 2);
     ADD_C(chunk, CSTR_AS_OBJ(text));
     if (hl_array.size > 0) {
-      if (hl_id > 0) {
+      if (hl_id >= 0) {
         ADD_C(hl_array, hl_group_name(hl_id, hl_name));
       }
       ADD_C(chunk, ARRAY_OBJ(hl_array));
-    } else if (hl_id > 0) {
+    } else if (hl_id >= 0) {
       ADD_C(chunk, hl_group_name(hl_id, hl_name));
     }
     ADD_C(chunks, ARRAY_OBJ(chunk));
@@ -489,8 +489,8 @@ Array nvim_buf_get_extmarks(Buffer buffer, Integer ns_id, Object start, Object e
 ///                   used together with virt_text.
 ///               - url: A URL to associate with this extmark. In the TUI, the OSC 8 control
 ///                   sequence is used to generate a clickable hyperlink to this URL.
-///               - scoped: boolean that indicates that the extmark should only be
-///                   displayed in the namespace scope. (experimental)
+///               - scoped: boolean (EXPERIMENTAL) enables "scoping" for the extmark. See
+///                 |nvim__win_add_ns()|
 ///
 /// @param[out]  err   Error details, if any
 /// @return Id of the created/updated extmark
@@ -682,7 +682,7 @@ Integer nvim_buf_set_extmark(Buffer buffer, Integer ns_id, Integer line, Integer
     goto error;
   });
 
-  size_t len = 0;
+  colnr_T len = 0;
 
   if (HAS_KEY(opts, set_extmark, spell)) {
     hl.flags |= (opts->spell) ? kSHSpellOn : kSHSpellOff;
@@ -712,16 +712,16 @@ 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 = opts->ephemeral ? MAXCOL : strlen(ml_get_buf(buf, (linenr_T)line + 1));
+    len = opts->ephemeral ? MAXCOL : ml_get_buf_len(buf, (linenr_T)line + 1);
   }
 
   if (col == -1) {
-    col = (Integer)len;
-  } else if (col > (Integer)len) {
+    col = len;
+  } else if (col > len) {
     VALIDATE_RANGE(!strict, "col", {
       goto error;
     });
-    col = (Integer)len;
+    col = len;
   } else if (col < -1) {
     VALIDATE_RANGE(false, "col", {
       goto error;
@@ -730,7 +730,7 @@ 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 = opts->ephemeral ? MAXCOL : strlen(ml_get_buf(buf, (linenr_T)line2 + 1));
+      len = opts->ephemeral ? MAXCOL : ml_get_buf_len(buf, (linenr_T)line2 + 1);
     } else if (line2 == buf->b_ml.ml_line_count) {
       // We are trying to add an extmark past final newline
       len = 0;
@@ -738,11 +738,11 @@ Integer nvim_buf_set_extmark(Buffer buffer, Integer ns_id, Integer line, Integer
       // reuse len from before
       line2 = (int)line;
     }
-    if (col2 > (Integer)len) {
+    if (col2 > len) {
       VALIDATE_RANGE(!strict, "end_col", {
         goto error;
       });
-      col2 = (int)len;
+      col2 = len;
     }
   } else if (line2 >= 0) {
     col2 = 0;
@@ -761,32 +761,20 @@ Integer nvim_buf_set_extmark(Buffer buffer, Integer ns_id, Integer line, Integer
       col2 = c;
     }
 
-    DecorPriority subpriority = DECOR_PRIORITY_BASE;
-    if (HAS_KEY(opts, set_extmark, _subpriority)) {
-      VALIDATE_RANGE((opts->_subpriority >= 0 && opts->_subpriority <= UINT16_MAX),
-                     "_subpriority", {
-        goto error;
-      });
-      subpriority = (DecorPriority)opts->_subpriority;
-    }
-
     if (kv_size(virt_text.data.virt_text)) {
-      decor_range_add_virt(&decor_state, r, c, line2, col2, decor_put_vt(virt_text, NULL), true,
-                           subpriority);
+      decor_range_add_virt(&decor_state, r, c, line2, col2, decor_put_vt(virt_text, NULL), true);
     }
     if (kv_size(virt_lines.data.virt_lines)) {
-      decor_range_add_virt(&decor_state, r, c, line2, col2, decor_put_vt(virt_lines, NULL), true,
-                           subpriority);
+      decor_range_add_virt(&decor_state, r, c, line2, col2, decor_put_vt(virt_lines, NULL), true);
     }
     if (url != NULL) {
       DecorSignHighlight sh = DECOR_SIGN_HIGHLIGHT_INIT;
       sh.url = url;
-      decor_range_add_sh(&decor_state, r, c, line2, col2, &sh, true, 0, 0, subpriority);
+      decor_range_add_sh(&decor_state, r, c, line2, col2, &sh, true, 0, 0);
     }
     if (has_hl) {
       DecorSignHighlight sh = decor_sh_from_inline(hl);
-      decor_range_add_sh(&decor_state, r, c, line2, col2, &sh, true, (uint32_t)ns_id, id,
-                         subpriority);
+      decor_range_add_sh(&decor_state, r, c, line2, col2, &sh, true, (uint32_t)ns_id, id);
     }
   } else {
     if (opts->ephemeral) {
@@ -1177,7 +1165,7 @@ VirtText parse_virt_text(Array chunks, Error *err, int *width)
 
     String str = chunk.items[0].data.string;
 
-    int hl_id = 0;
+    int hl_id = -1;
     if (chunk.size == 2) {
       Object hl = chunk.items[1];
       if (hl.type == kObjectTypeArray) {
@@ -1227,13 +1215,15 @@ String nvim__buf_debug_extmarks(Buffer buffer, Boolean keys, Boolean dot, Error
   return mt_inspect(buf->b_marktree, keys, dot);
 }
 
-/// Adds the namespace scope to the window.
+/// EXPERIMENTAL: this API will change in the future.
+///
+/// Scopes a namespace to the a window, so extmarks in the namespace will be active only in the
+/// given window.
 ///
 /// @param window Window handle, or 0 for current window
-/// @param ns_id the namespace to add
+/// @param ns_id Namespace
 /// @return true if the namespace was added, else false
-Boolean nvim_win_add_ns(Window window, Integer ns_id, Error *err)
-  FUNC_API_SINCE(12)
+Boolean nvim__win_add_ns(Window window, Integer ns_id, Error *err)
 {
   win_T *win = find_window_by_handle(window, err);
   if (!win) {
@@ -1246,17 +1236,20 @@ Boolean nvim_win_add_ns(Window window, Integer ns_id, Error *err)
 
   set_put(uint32_t, &win->w_ns_set, (uint32_t)ns_id);
 
-  changed_window_setting_win(win);
+  if (map_has(uint32_t, win->w_buffer->b_extmark_ns, (uint32_t)ns_id)) {
+    changed_window_setting(win);
+  }
 
   return true;
 }
 
-/// Gets all the namespaces scopes associated with a window.
+/// EXPERIMENTAL: this API will change in the future.
+///
+/// Gets the namespace scopes for a given window.
 ///
 /// @param window Window handle, or 0 for current window
 /// @return a list of namespaces ids
-ArrayOf(Integer) nvim_win_get_ns(Window window, Arena *arena, Error *err)
-  FUNC_API_SINCE(12)
+ArrayOf(Integer) nvim__win_get_ns(Window window, Arena *arena, Error *err)
 {
   win_T *win = find_window_by_handle(window, err);
   if (!win) {
@@ -1272,13 +1265,14 @@ ArrayOf(Integer) nvim_win_get_ns(Window window, Arena *arena, Error *err)
   return rv;
 }
 
-/// Removes the namespace scope from the window.
+/// EXPERIMENTAL: this API will change in the future.
+///
+/// Unscopes a namespace (un-binds it from the given scope).
 ///
 /// @param window Window handle, or 0 for current window
 /// @param ns_id the namespace to remove
 /// @return true if the namespace was removed, else false
-Boolean nvim_win_remove_ns(Window window, Integer ns_id, Error *err)
-  FUNC_API_SINCE(12)
+Boolean nvim__win_del_ns(Window window, Integer ns_id, Error *err)
 {
   win_T *win = find_window_by_handle(window, err);
   if (!win) {
@@ -1291,7 +1285,9 @@ Boolean nvim_win_remove_ns(Window window, Integer ns_id, Error *err)
 
   set_del(uint32_t, &win->w_ns_set, (uint32_t)ns_id);
 
-  changed_window_setting_win(win);
+  if (map_has(uint32_t, win->w_buffer->b_extmark_ns, (uint32_t)ns_id)) {
+    changed_window_setting(win);
+  }
 
   return true;
 }
diff --git a/src/nvim/api/keysets_defs.h b/src/nvim/api/keysets_defs.h
index fe91d9760d..00d8aa8428 100644
--- a/src/nvim/api/keysets_defs.h
+++ b/src/nvim/api/keysets_defs.h
@@ -56,8 +56,6 @@ typedef struct {
   Boolean undo_restore;
   String url;
   Boolean scoped;
-
-  Integer _subpriority;
 } Dict(set_extmark);
 
 typedef struct {
@@ -375,3 +373,17 @@ typedef struct {
   Boolean ignore_blank_lines;
   Boolean indent_heuristic;
 } Dict(xdl_diff);
+
+typedef struct {
+  OptionalKeys is_set__redraw_;
+  Boolean flush;
+  Boolean cursor;
+  Boolean valid;
+  Boolean statuscolumn;
+  Boolean statusline;
+  Boolean tabline;
+  Boolean winbar;
+  Array range;
+  Window win;
+  Buffer buf;
+} Dict(redraw);
diff --git a/src/nvim/api/private/converter.c b/src/nvim/api/private/converter.c
index a70ef1e50b..a78d78c057 100644
--- a/src/nvim/api/private/converter.c
+++ b/src/nvim/api/private/converter.c
@@ -76,8 +76,7 @@ static Object typval_cbuf_to_obj(EncodedData *edata, const char *data, size_t le
   do { \
     ufunc_T *fp = find_func(fun); \
     if (fp != NULL && (fp->uf_flags & FC_LUAREF)) { \
-      LuaRef ref = api_new_luaref(fp->uf_luaref); \
-      kvi_push(edata->stack, LUAREF_OBJ(ref)); \
+      kvi_push(edata->stack, LUAREF_OBJ(api_new_luaref(fp->uf_luaref))); \
     } else { \
       TYPVAL_ENCODE_CONV_NIL(tv); \
     } \
diff --git a/src/nvim/api/private/helpers.c b/src/nvim/api/private/helpers.c
index 1cd98aa0c4..a17e78cc31 100644
--- a/src/nvim/api/private/helpers.c
+++ b/src/nvim/api/private/helpers.c
@@ -524,10 +524,10 @@ String buf_get_text(buf_T *buf, int64_t lnum, int64_t start_col, int64_t end_col
   }
 
   char *bufstr = ml_get_buf(buf, (linenr_T)lnum);
-  size_t line_length = strlen(bufstr);
+  colnr_T line_length = ml_get_buf_len(buf, (linenr_T)lnum);
 
-  start_col = start_col < 0 ? (int64_t)line_length + start_col + 1 : start_col;
-  end_col = end_col < 0 ? (int64_t)line_length + end_col + 1 : end_col;
+  start_col = start_col < 0 ? line_length + start_col + 1 : start_col;
+  end_col = end_col < 0 ? line_length + end_col + 1 : end_col;
 
   if (start_col >= MAXCOL || end_col >= MAXCOL) {
     api_set_error(err, kErrorTypeValidation, "Column index is too high");
@@ -539,7 +539,7 @@ String buf_get_text(buf_T *buf, int64_t lnum, int64_t start_col, int64_t end_col
     return rv;
   }
 
-  if ((size_t)start_col >= line_length) {
+  if (start_col >= line_length) {
     return rv;
   }
 
diff --git a/src/nvim/api/tabpage.c b/src/nvim/api/tabpage.c
index 040abb1e3f..56a3f1cf23 100644
--- a/src/nvim/api/tabpage.c
+++ b/src/nvim/api/tabpage.c
@@ -146,7 +146,11 @@ void nvim_tabpage_set_win(Tabpage tabpage, Window win, Error *err)
   }
 
   if (tp == curtab) {
-    win_enter(wp, true);
+    try_start();
+    win_goto(wp);
+    if (!try_end(err) && curwin != wp) {
+      api_set_error(err, kErrorTypeException, "Failed to switch to window %d", win);
+    }
   } else if (tp->tp_curwin != wp) {
     tp->tp_prevwin = tp->tp_curwin;
     tp->tp_curwin = wp;
diff --git a/src/nvim/api/ui.c b/src/nvim/api/ui.c
index 692e3f95fc..fdf25c75d7 100644
--- a/src/nvim/api/ui.c
+++ b/src/nvim/api/ui.c
@@ -67,7 +67,6 @@ static void mpack_str_small(char **buf, const char *str, size_t len)
 static void remote_ui_destroy(RemoteUI *ui)
   FUNC_ATTR_NONNULL_ALL
 {
-  kv_destroy(ui->call_buf);
   xfree(ui->packer.startptr);
   XFREE_CLEAR(ui->term_name);
   xfree(ui);
@@ -190,8 +189,6 @@ void nvim_ui_attach(uint64_t channel_id, Integer width, Integer height, Dictiona
     .anydata = ui,
   };
   ui->wildmenu_active = false;
-  ui->call_buf = (Array)ARRAY_DICT_INIT;
-  kv_ensure_space(ui->call_buf, 16);
 
   pmap_put(uint64_t)(&connected_uis, channel_id, ui);
   ui_attach_impl(ui, channel_id);
@@ -533,7 +530,8 @@ static void ui_alloc_buf(RemoteUI *ui)
 
 static void prepare_call(RemoteUI *ui, const char *name)
 {
-  if (ui->packer.startptr && BUF_POS(ui) > UI_BUF_SIZE - EVENT_BUF_SIZE) {
+  if (ui->packer.startptr
+      && (BUF_POS(ui) > UI_BUF_SIZE - EVENT_BUF_SIZE || ui->ncells_pending >= 500)) {
     ui_flush_buf(ui);
   }
 
@@ -582,7 +580,7 @@ static void ui_flush_callback(PackerBuffer *packer)
 
 void remote_ui_grid_clear(RemoteUI *ui, Integer grid)
 {
-  Array args = ui->call_buf;
+  MAXSIZE_TEMP_ARRAY(args, 1);
   if (ui->ui_ext[kUILinegrid]) {
     ADD_C(args, INTEGER_OBJ(grid));
   }
@@ -592,7 +590,7 @@ void remote_ui_grid_clear(RemoteUI *ui, Integer grid)
 
 void remote_ui_grid_resize(RemoteUI *ui, Integer grid, Integer width, Integer height)
 {
-  Array args = ui->call_buf;
+  MAXSIZE_TEMP_ARRAY(args, 3);
   if (ui->ui_ext[kUILinegrid]) {
     ADD_C(args, INTEGER_OBJ(grid));
   } else {
@@ -608,7 +606,7 @@ void remote_ui_grid_scroll(RemoteUI *ui, Integer grid, Integer top, Integer bot,
                            Integer right, Integer rows, Integer cols)
 {
   if (ui->ui_ext[kUILinegrid]) {
-    Array args = ui->call_buf;
+    MAXSIZE_TEMP_ARRAY(args, 7);
     ADD_C(args, INTEGER_OBJ(grid));
     ADD_C(args, INTEGER_OBJ(top));
     ADD_C(args, INTEGER_OBJ(bot));
@@ -618,20 +616,19 @@ void remote_ui_grid_scroll(RemoteUI *ui, Integer grid, Integer top, Integer bot,
     ADD_C(args, INTEGER_OBJ(cols));
     push_call(ui, "grid_scroll", args);
   } else {
-    Array args = ui->call_buf;
+    MAXSIZE_TEMP_ARRAY(args, 4);
     ADD_C(args, INTEGER_OBJ(top));
     ADD_C(args, INTEGER_OBJ(bot - 1));
     ADD_C(args, INTEGER_OBJ(left));
     ADD_C(args, INTEGER_OBJ(right - 1));
     push_call(ui, "set_scroll_region", args);
 
-    args = ui->call_buf;
+    kv_size(args) = 0;
     ADD_C(args, INTEGER_OBJ(rows));
     push_call(ui, "scroll", args);
 
-    // some clients have "clear" being affected by scroll region,
-    // so reset it.
-    args = ui->call_buf;
+    // some clients have "clear" being affected by scroll region, so reset it.
+    kv_size(args) = 0;
     ADD_C(args, INTEGER_OBJ(0));
     ADD_C(args, INTEGER_OBJ(ui->height - 1));
     ADD_C(args, INTEGER_OBJ(0));
@@ -646,7 +643,7 @@ void remote_ui_default_colors_set(RemoteUI *ui, Integer rgb_fg, Integer rgb_bg,
   if (!ui->ui_ext[kUITermColors]) {
     HL_SET_DEFAULT_COLORS(rgb_fg, rgb_bg, rgb_sp);
   }
-  Array args = ui->call_buf;
+  MAXSIZE_TEMP_ARRAY(args, 5);
   ADD_C(args, INTEGER_OBJ(rgb_fg));
   ADD_C(args, INTEGER_OBJ(rgb_bg));
   ADD_C(args, INTEGER_OBJ(rgb_sp));
@@ -656,15 +653,15 @@ void remote_ui_default_colors_set(RemoteUI *ui, Integer rgb_fg, Integer rgb_bg,
 
   // Deprecated
   if (!ui->ui_ext[kUILinegrid]) {
-    args = ui->call_buf;
+    kv_size(args) = 0;
     ADD_C(args, INTEGER_OBJ(ui->rgb ? rgb_fg : cterm_fg - 1));
     push_call(ui, "update_fg", args);
 
-    args = ui->call_buf;
+    kv_size(args) = 0;
     ADD_C(args, INTEGER_OBJ(ui->rgb ? rgb_bg : cterm_bg - 1));
     push_call(ui, "update_bg", args);
 
-    args = ui->call_buf;
+    kv_size(args) = 0;
     ADD_C(args, INTEGER_OBJ(ui->rgb ? rgb_sp : -1));
     push_call(ui, "update_sp", args);
   }
@@ -677,7 +674,7 @@ void remote_ui_hl_attr_define(RemoteUI *ui, Integer id, HlAttrs rgb_attrs, HlAtt
     return;
   }
 
-  Array args = ui->call_buf;
+  MAXSIZE_TEMP_ARRAY(args, 4);
   ADD_C(args, INTEGER_OBJ(id));
   MAXSIZE_TEMP_DICT(rgb, HLATTRS_DICT_SIZE);
   MAXSIZE_TEMP_DICT(cterm, HLATTRS_DICT_SIZE);
@@ -705,14 +702,14 @@ void remote_ui_hl_attr_define(RemoteUI *ui, Integer id, HlAttrs rgb_attrs, HlAtt
 
 void remote_ui_highlight_set(RemoteUI *ui, int id)
 {
-  Array args = ui->call_buf;
-
   if (ui->hl_id == id) {
     return;
   }
+
   ui->hl_id = id;
   MAXSIZE_TEMP_DICT(dict, HLATTRS_DICT_SIZE);
   hlattrs2dict(&dict, NULL, syn_attr2entry(id), ui->rgb, false);
+  MAXSIZE_TEMP_ARRAY(args, 1);
   ADD_C(args, DICTIONARY_OBJ(dict));
   push_call(ui, "highlight_set", args);
 }
@@ -721,7 +718,7 @@ void remote_ui_highlight_set(RemoteUI *ui, int id)
 void remote_ui_grid_cursor_goto(RemoteUI *ui, Integer grid, Integer row, Integer col)
 {
   if (ui->ui_ext[kUILinegrid]) {
-    Array args = ui->call_buf;
+    MAXSIZE_TEMP_ARRAY(args, 3);
     ADD_C(args, INTEGER_OBJ(grid));
     ADD_C(args, INTEGER_OBJ(row));
     ADD_C(args, INTEGER_OBJ(col));
@@ -741,7 +738,7 @@ void remote_ui_cursor_goto(RemoteUI *ui, Integer row, Integer col)
   }
   ui->client_row = row;
   ui->client_col = col;
-  Array args = ui->call_buf;
+  MAXSIZE_TEMP_ARRAY(args, 2);
   ADD_C(args, INTEGER_OBJ(row));
   ADD_C(args, INTEGER_OBJ(col));
   push_call(ui, "cursor_goto", args);
@@ -750,7 +747,7 @@ void remote_ui_cursor_goto(RemoteUI *ui, Integer row, Integer col)
 void remote_ui_put(RemoteUI *ui, const char *cell)
 {
   ui->client_col++;
-  Array args = ui->call_buf;
+  MAXSIZE_TEMP_ARRAY(args, 1);
   ADD_C(args, CSTR_AS_OBJ(cell));
   push_call(ui, "put", args);
 }
@@ -781,11 +778,14 @@ void remote_ui_raw_line(RemoteUI *ui, Integer grid, Integer row, Integer startco
     for (size_t i = 0; i < ncells; i++) {
       repeat++;
       if (i == ncells - 1 || attrs[i] != attrs[i + 1] || chunk[i] != chunk[i + 1]) {
-        if (UI_BUF_SIZE - BUF_POS(ui) < 2 * (1 + 2 + sizeof(schar_T) + 5 + 5) + 1) {
+        if (UI_BUF_SIZE - BUF_POS(ui) < 2 * (1 + 2 + MAX_SCHAR_SIZE + 5 + 5) + 1
+            || ui->ncells_pending >= 500) {
           // close to overflowing the redraw buffer. finish this event,
           // flush, and start a new "grid_line" event at the current position.
           // For simplicity leave place for the final "clear" element
           // as well, hence the factor of 2 in the check.
+          // Also if there is a lot of packed cells, pass them of to the UI to
+          // let it start processing them
           mpack_w2(&lenpos, nelem);
 
           // We only ever set the wrap field on the final "grid_line" event for the line.
@@ -831,11 +831,6 @@ void remote_ui_raw_line(RemoteUI *ui, Integer grid, Integer row, Integer startco
     }
     mpack_w2(&lenpos, nelem);
     mpack_bool(buf, flags & kLineFlagWrap);
-
-    if (ui->ncells_pending > 500) {
-      // pass off cells to UI to let it start processing them
-      ui_flush_buf(ui);
-    }
   } else {
     for (int i = 0; i < endcol - startcol; i++) {
       remote_ui_cursor_goto(ui, row, startcol + i);
@@ -951,12 +946,12 @@ void remote_ui_event(RemoteUI *ui, char *name, Array args)
       push_call(ui, name, new_args);
       goto free_ret;
     } else if (strequal(name, "cmdline_block_show")) {
-      Array new_args = ui->call_buf;
       Array block = args.items[0].data.array;
       Array new_block = arena_array(&arena, block.size);
       for (size_t i = 0; i < block.size; i++) {
         ADD_C(new_block, ARRAY_OBJ(translate_contents(ui, block.items[i].data.array, &arena)));
       }
+      MAXSIZE_TEMP_ARRAY(new_args, 1);
       ADD_C(new_args, ARRAY_OBJ(new_block));
       push_call(ui, name, new_args);
       goto free_ret;
@@ -973,18 +968,18 @@ void remote_ui_event(RemoteUI *ui, char *name, Array args)
       ui->wildmenu_active = (args.items[4].data.integer == -1)
                             || !ui->ui_ext[kUIPopupmenu];
       if (ui->wildmenu_active) {
-        Array new_args = ui->call_buf;
         Array items = args.items[0].data.array;
         Array new_items = arena_array(&arena, items.size);
         for (size_t i = 0; i < items.size; i++) {
           ADD_C(new_items, items.items[i].data.array.items[0]);
         }
+        MAXSIZE_TEMP_ARRAY(new_args, 1);
         ADD_C(new_args, ARRAY_OBJ(new_items));
         push_call(ui, "wildmenu_show", new_args);
         if (args.items[1].data.integer != -1) {
-          Array new_args2 = ui->call_buf;
-          ADD_C(new_args2, args.items[1]);
-          push_call(ui, "wildmenu_select", new_args2);
+          kv_size(new_args) = 0;
+          ADD_C(new_args, args.items[1]);
+          push_call(ui, "wildmenu_select", new_args);
         }
         goto free_ret;
       }
diff --git a/src/nvim/api/ui_events.in.h b/src/nvim/api/ui_events.in.h
index c2f02c34f8..2bd8792d71 100644
--- a/src/nvim/api/ui_events.in.h
+++ b/src/nvim/api/ui_events.in.h
@@ -118,6 +118,10 @@ void win_viewport(Integer grid, Window win, Integer topline, Integer botline, In
                   Integer curcol, Integer line_count, Integer scroll_delta)
   FUNC_API_SINCE(7) FUNC_API_CLIENT_IGNORE;
 
+void win_viewport_margins(Integer grid, Window win, Integer top, Integer bottom, Integer left,
+                          Integer right)
+  FUNC_API_SINCE(12) FUNC_API_CLIENT_IGNORE;
+
 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;
 
diff --git a/src/nvim/api/vim.c b/src/nvim/api/vim.c
index 84a2f24dbc..fc780e1248 100644
--- a/src/nvim/api/vim.c
+++ b/src/nvim/api/vim.c
@@ -45,10 +45,12 @@
 #include "nvim/keycodes.h"
 #include "nvim/log.h"
 #include "nvim/lua/executor.h"
+#include "nvim/lua/treesitter.h"
 #include "nvim/macros_defs.h"
 #include "nvim/mapping.h"
 #include "nvim/mark.h"
 #include "nvim/mark_defs.h"
+#include "nvim/math.h"
 #include "nvim/mbyte.h"
 #include "nvim/memline.h"
 #include "nvim/memory.h"
@@ -167,7 +169,7 @@ Dictionary nvim_get_hl(Integer ns_id, Dict(get_highlight) *opts, Arena *arena, E
 /// @param[out] err Error details, if any
 ///
 // TODO(bfredl): val should take update vs reset flag
-void nvim_set_hl(Integer ns_id, String name, Dict(highlight) *val, Error *err)
+void nvim_set_hl(uint64_t channel_id, Integer ns_id, String name, Dict(highlight) *val, Error *err)
   FUNC_API_SINCE(7)
 {
   int hl_id = syn_check_group(name.data, name.size);
@@ -184,7 +186,9 @@ void nvim_set_hl(Integer ns_id, String name, Dict(highlight) *val, Error *err)
 
   HlAttrs attrs = dict2hlattrs(val, true, &link_id, err);
   if (!ERROR_SET(err)) {
-    ns_hl_def((NS)ns_id, hl_id, attrs, link_id, val);
+    WITH_SCRIPT_CONTEXT(channel_id, {
+      ns_hl_def((NS)ns_id, hl_id, attrs, link_id, val);
+    });
   }
 }
 
@@ -275,6 +279,7 @@ void nvim_feedkeys(String keys, String mode, Boolean escape_ks)
   bool typed = false;
   bool execute = false;
   bool dangerous = false;
+  bool lowlevel = false;
 
   for (size_t i = 0; i < mode.size; i++) {
     switch (mode.data[i]) {
@@ -290,6 +295,8 @@ void nvim_feedkeys(String keys, String mode, Boolean escape_ks)
       execute = true; break;
     case '!':
       dangerous = true; break;
+    case 'L':
+      lowlevel = true; break;
     }
   }
 
@@ -305,10 +312,14 @@ void nvim_feedkeys(String keys, String mode, Boolean escape_ks)
   } else {
     keys_esc = keys.data;
   }
-  ins_typebuf(keys_esc, (remap ? REMAP_YES : REMAP_NONE),
-              insert ? 0 : typebuf.tb_len, !typed, false);
-  if (vgetc_busy) {
-    typebuf_was_filled = true;
+  if (lowlevel) {
+    input_enqueue_raw(cstr_as_string(keys_esc));
+  } else {
+    ins_typebuf(keys_esc, (remap ? REMAP_YES : REMAP_NONE),
+                insert ? 0 : typebuf.tb_len, !typed, false);
+    if (vgetc_busy) {
+      typebuf_was_filled = true;
+    }
   }
 
   if (escape_ks) {
@@ -876,6 +887,11 @@ void nvim_set_current_buf(Buffer buffer, Error *err)
     return;
   }
 
+  if (curwin->w_p_wfb) {
+    api_set_error(err, kErrorTypeException, "%s", e_winfixbuf_cannot_go_to_buffer);
+    return;
+  }
+
   try_start();
   int result = do_buffer(DOBUF_GOTO, DOBUF_FIRST, FORWARD, buf->b_fnum, 0);
   if (!try_end(err) && result == FAIL) {
@@ -953,21 +969,21 @@ Buffer nvim_create_buf(Boolean listed, Boolean scratch, Error *err)
   FUNC_API_SINCE(6)
 {
   try_start();
+  // Block autocommands for now so they don't mess with the buffer before we
+  // finish configuring it.
+  block_autocmds();
+
   buf_T *buf = buflist_new(NULL, NULL, 0,
                            BLN_NOOPT | BLN_NEW | (listed ? BLN_LISTED : 0));
-  try_end(err);
   if (buf == NULL) {
+    unblock_autocmds();
     goto fail;
   }
 
   // Open the memline for the buffer. This will avoid spurious autocmds when
   // a later nvim_buf_set_lines call would have needed to "open" the buffer.
-  try_start();
-  block_autocmds();
-  int status = ml_open(buf);
-  unblock_autocmds();
-  try_end(err);
-  if (status == FAIL) {
+  if (ml_open(buf) == FAIL) {
+    unblock_autocmds();
     goto fail;
   }
 
@@ -978,21 +994,39 @@ Buffer nvim_create_buf(Boolean listed, Boolean scratch, Error *err)
   buf->b_last_changedtick_pum = buf_get_changedtick(buf);
 
   // Only strictly needed for scratch, but could just as well be consistent
-  // and do this now. buffer is created NOW, not when it latter first happen
+  // and do this now. Buffer is created NOW, not when it later first happens
   // to reach a window or aucmd_prepbuf() ..
   buf_copy_options(buf, BCO_ENTER | BCO_NOHELP);
 
   if (scratch) {
-    set_string_option_direct_in_buf(buf, kOptBufhidden, "hide", OPT_LOCAL, 0);
-    set_string_option_direct_in_buf(buf, kOptBuftype, "nofile", OPT_LOCAL, 0);
+    set_option_direct_for(kOptBufhidden, STATIC_CSTR_AS_OPTVAL("hide"), OPT_LOCAL, 0, kOptReqBuf,
+                          buf);
+    set_option_direct_for(kOptBuftype, STATIC_CSTR_AS_OPTVAL("nofile"), OPT_LOCAL, 0, kOptReqBuf,
+                          buf);
     assert(buf->b_ml.ml_mfp->mf_fd < 0);  // ml_open() should not have opened swapfile already
     buf->b_p_swf = false;
     buf->b_p_ml = false;
   }
+
+  unblock_autocmds();
+
+  bufref_T bufref;
+  set_bufref(&bufref, buf);
+  if (apply_autocmds(EVENT_BUFNEW, NULL, NULL, false, buf)
+      && !bufref_valid(&bufref)) {
+    goto fail;
+  }
+  if (listed
+      && apply_autocmds(EVENT_BUFADD, NULL, NULL, false, buf)
+      && !bufref_valid(&bufref)) {
+    goto fail;
+  }
+
+  try_end(err);
   return buf->b_fnum;
 
 fail:
-  if (!ERROR_SET(err)) {
+  if (!try_end(err)) {
     api_set_error(err, kErrorTypeException, "Failed to create buffer");
   }
   return 0;
@@ -1300,36 +1334,6 @@ void nvim_put(ArrayOf(String) lines, String type, Boolean after, Boolean follow,
   });
 }
 
-/// Subscribes to event broadcasts.
-///
-/// @param channel_id Channel id (passed automatically by the dispatcher)
-/// @param event      Event type string
-void nvim_subscribe(uint64_t channel_id, String event)
-  FUNC_API_SINCE(1) FUNC_API_REMOTE_ONLY
-{
-  size_t length = (event.size < METHOD_MAXLEN ? event.size : METHOD_MAXLEN);
-  char e[METHOD_MAXLEN + 1];
-  memcpy(e, event.data, length);
-  e[length] = NUL;
-  rpc_subscribe(channel_id, e);
-}
-
-/// Unsubscribes to event broadcasts.
-///
-/// @param channel_id Channel id (passed automatically by the dispatcher)
-/// @param event      Event type string
-void nvim_unsubscribe(uint64_t channel_id, String event)
-  FUNC_API_SINCE(1) FUNC_API_REMOTE_ONLY
-{
-  size_t length = (event.size < METHOD_MAXLEN
-                   ? event.size
-                   : METHOD_MAXLEN);
-  char e[METHOD_MAXLEN + 1];
-  memcpy(e, event.data, length);
-  e[length] = NUL;
-  rpc_unsubscribe(channel_id, e);
-}
-
 /// Returns the 24-bit RGB value of a |nvim_get_color_map()| color name or
 /// "#rrggbb" hexadecimal string.
 ///
@@ -1666,90 +1670,6 @@ Array nvim_list_chans(Arena *arena)
   return channel_all_info(arena);
 }
 
-/// Calls many API methods atomically.
-///
-/// This has two main usages:
-/// 1. To perform several requests from an async context atomically, i.e.
-///    without interleaving redraws, RPC requests from other clients, or user
-///    interactions (however API methods may trigger autocommands or event
-///    processing which have such side effects, e.g. |:sleep| may wake timers).
-/// 2. To minimize RPC overhead (roundtrips) of a sequence of many requests.
-///
-/// @param channel_id
-/// @param calls an array of calls, where each call is described by an array
-///              with two elements: the request name, and an array of arguments.
-/// @param[out] err Validation error details (malformed `calls` parameter),
-///             if any. Errors from batched calls are given in the return value.
-///
-/// @return Array of two elements. The first is an array of return
-/// values. The second is NIL if all calls succeeded. If a call resulted in
-/// 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, Arena *arena, Error *err)
-  FUNC_API_SINCE(1) FUNC_API_REMOTE_ONLY
-{
-  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
-  for (i = 0; i < calls.size; i++) {
-    VALIDATE_T("'calls' item", kObjectTypeArray, calls.items[i].type, {
-      goto theend;
-    });
-    Array call = calls.items[i].data.array;
-    VALIDATE_EXP((call.size == 2), "'calls' item", "2-item Array", NULL, {
-      goto theend;
-    });
-    VALIDATE_T("name", kObjectTypeString, call.items[0].type, {
-      goto theend;
-    });
-    String name = call.items[0].data.string;
-    VALIDATE_T("call args", kObjectTypeArray, call.items[1].type, {
-      goto theend;
-    });
-    Array args = call.items[1].data.array;
-
-    MsgpackRpcRequestHandler handler =
-      msgpack_rpc_get_handler_for(name.data,
-                                  name.size,
-                                  &nested_error);
-
-    if (ERROR_SET(&nested_error)) {
-      break;
-    }
-
-    Object result = handler.fn(channel_id, args, arena, &nested_error);
-    if (ERROR_SET(&nested_error)) {
-      // error handled after loop
-      break;
-    }
-    // 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.ret_alloc) {
-      api_free_object(result);
-    }
-  }
-
-  ADD_C(rv, ARRAY_OBJ(results));
-  if (ERROR_SET(&nested_error)) {
-    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_C(rv, NIL);
-  }
-
-theend:
-  api_clear_error(&nested_error);
-  return rv;
-}
-
 /// Writes a message to vim output or error buffer. The string is split
 /// and flushed after each newline. Incomplete lines are kept for writing
 /// later.
@@ -1858,12 +1778,13 @@ Float nvim__id_float(Float flt)
 /// @return Map of various internal stats.
 Dictionary nvim__stats(Arena *arena)
 {
-  Dictionary rv = arena_dict(arena, 5);
+  Dictionary rv = arena_dict(arena, 6);
   PUT_C(rv, "fsync", INTEGER_OBJ(g_stats.fsync));
   PUT_C(rv, "log_skip", INTEGER_OBJ(g_stats.log_skip));
   PUT_C(rv, "lua_refcount", INTEGER_OBJ(nlua_get_global_ref_count()));
   PUT_C(rv, "redraw", INTEGER_OBJ(g_stats.redraw));
   PUT_C(rv, "arena_alloc_count", INTEGER_OBJ((Integer)arena_alloc_count));
+  PUT_C(rv, "ts_query_parse_count", INTEGER_OBJ((Integer)tslua_query_parse_count));
   return rv;
 }
 
@@ -2332,20 +2253,18 @@ void nvim_error_event(uint64_t channel_id, Integer lvl, String data)
   ELOG("async error on channel %" PRId64 ": %s", channel_id, data.size ? data.data : "");
 }
 
-/// Set info for the completion candidate index.
-/// if the info was shown in a window, then the
-/// window and buffer ids are returned for further
-/// customization. If the text was not shown, an
-/// empty dict is returned.
+/// EXPERIMENTAL: this API may change in the future.
 ///
-/// @param index  the completion candidate index
+/// Sets info for the completion item at the given index. If the info text was shown in a window,
+/// returns the window and buffer ids, or empty dict if not shown.
+///
+/// @param index  Completion candidate index
 /// @param opts   Optional parameters.
 ///       - info: (string) info text.
 /// @return Dictionary containing these keys:
 ///       - winid: (number) floating window id
 ///       - bufnr: (number) buffer id in floating window
-Dictionary nvim_complete_set(Integer index, Dict(complete_set) *opts, Arena *arena)
-  FUNC_API_SINCE(12)
+Dictionary nvim__complete_set(Integer index, Dict(complete_set) *opts, Arena *arena)
 {
   Dictionary rv = arena_dict(arena, 2);
   if (HAS_KEY(opts, complete_set, info)) {
@@ -2357,3 +2276,159 @@ Dictionary nvim_complete_set(Integer index, Dict(complete_set) *opts, Arena *are
   }
   return rv;
 }
+
+static void redraw_status(win_T *wp, Dict(redraw) *opts, bool *flush)
+{
+  if (opts->statuscolumn && *wp->w_p_stc != NUL) {
+    wp->w_nrwidth_line_count = 0;
+    changed_window_setting(wp);
+  }
+  win_grid_alloc(wp);
+
+  // Flush later in case winbar was just hidden or shown for the first time, or
+  // statuscolumn is being drawn.
+  if (wp->w_lines_valid == 0) {
+    *flush = true;
+  }
+
+  // Mark for redraw in case flush will happen, otherwise redraw now.
+  if (*flush && (opts->statusline || opts->winbar)) {
+    wp->w_redr_status = true;
+  } else if (opts->statusline || opts->winbar) {
+    win_check_ns_hl(wp);
+    if (opts->winbar) {
+      win_redr_winbar(wp);
+    }
+    if (opts->statusline) {
+      win_redr_status(wp);
+    }
+    win_check_ns_hl(NULL);
+  }
+}
+
+/// EXPERIMENTAL: this API may change in the future.
+///
+/// Instruct Nvim to redraw various components.
+///
+/// @see |:redraw|
+///
+/// @param opts  Optional parameters.
+///               - win: Target a specific |window-ID| as described below.
+///               - buf: Target a specific buffer number as described below.
+///               - flush: Update the screen with pending updates.
+///               - valid: When present mark `win`, `buf`, or all windows for
+///                 redraw. When `true`, only redraw changed lines (useful for
+///                 decoration providers). When `false`, forcefully redraw.
+///               - range: Redraw a range in `buf`, the buffer in `win` or the
+///                 current buffer (useful for decoration providers). Expects a
+///                 tuple `[first, last]` with the first and last line number
+///                 of the range, 0-based end-exclusive |api-indexing|.
+///               - cursor: Immediately update cursor position on the screen in
+///                 `win` or the current window.
+///               - statuscolumn: Redraw the 'statuscolumn' in `buf`, `win` or
+///                 all windows.
+///               - statusline: Redraw the 'statusline' in `buf`, `win` or all
+///                 windows.
+///               - winbar: Redraw the 'winbar' in `buf`, `win` or all windows.
+///               - tabline: Redraw the 'tabline'.
+void nvim__redraw(Dict(redraw) *opts, Error *err)
+  FUNC_API_SINCE(12)
+{
+  win_T *win = NULL;
+  buf_T *buf = NULL;
+
+  if (HAS_KEY(opts, redraw, win)) {
+    win = find_window_by_handle(opts->win, err);
+    if (ERROR_SET(err)) {
+      return;
+    }
+  }
+
+  if (HAS_KEY(opts, redraw, buf)) {
+    VALIDATE(win == NULL, "%s", "cannot use both 'buf' and 'win'", {
+      return;
+    });
+    buf = find_buffer_by_handle(opts->buf, err);
+    if (ERROR_SET(err)) {
+      return;
+    }
+  }
+
+  int count = (win != NULL) + (buf != NULL);
+  VALIDATE(popcount(opts->is_set__redraw_) > count, "%s", "at least one action required", {
+    return;
+  });
+
+  if (HAS_KEY(opts, redraw, valid)) {
+    // UPD_VALID redraw type does not actually do anything on it's own. Setting
+    // it here without scrolling or changing buffer text seems pointless but
+    // the expectation is that this may be called by decoration providers whose
+    // "on_win" callback may set "w_redr_top/bot".
+    int type = opts->valid ? UPD_VALID : UPD_NOT_VALID;
+    if (win != NULL) {
+      redraw_later(win, type);
+    } else if (buf != NULL) {
+      redraw_buf_later(buf, type);
+    } else {
+      redraw_all_later(type);
+    }
+  }
+
+  if (HAS_KEY(opts, redraw, range)) {
+    VALIDATE(kv_size(opts->range) == 2
+             && kv_A(opts->range, 0).type == kObjectTypeInteger
+             && kv_A(opts->range, 1).type == kObjectTypeInteger
+             && kv_A(opts->range, 0).data.integer >= 0
+             && kv_A(opts->range, 1).data.integer >= -1,
+             "%s", "Invalid 'range': Expected 2-tuple of Integers", {
+      return;
+    });
+    linenr_T first = (linenr_T)kv_A(opts->range, 0).data.integer + 1;
+    linenr_T last = (linenr_T)kv_A(opts->range, 1).data.integer;
+    buf_T *rbuf = win ? win->w_buffer : (buf ? buf : curbuf);
+    if (last == -1) {
+      last = rbuf->b_ml.ml_line_count;
+    }
+    redraw_buf_range_later(rbuf, first, last);
+  }
+
+  if (opts->cursor) {
+    setcursor_mayforce(win ? win : curwin, true);
+  }
+
+  bool flush = opts->flush;
+  if (opts->tabline) {
+    // Flush later in case tabline was just hidden or shown for the first time.
+    if (redraw_tabline && firstwin->w_lines_valid == 0) {
+      flush = true;
+    } else {
+      draw_tabline();
+    }
+  }
+
+  bool save_lz = p_lz;
+  int save_rd = RedrawingDisabled;
+  RedrawingDisabled = 0;
+  p_lz = false;
+  if (opts->statuscolumn || opts->statusline || opts->winbar) {
+    if (win == NULL) {
+      FOR_ALL_WINDOWS_IN_TAB(wp, curtab) {
+        if (buf == NULL || wp->w_buffer == buf) {
+          redraw_status(wp, opts, &flush);
+        }
+      }
+    } else {
+      redraw_status(win, opts, &flush);
+    }
+  }
+
+  // Flush pending screen updates if "flush" or "clear" is true, or when
+  // redrawing a status component may have changed the grid dimensions.
+  if (flush && !cmdpreview) {
+    update_screen();
+  }
+  ui_flush();
+
+  RedrawingDisabled = save_rd;
+  p_lz = save_lz;
+}
diff --git a/src/nvim/api/win_config.c b/src/nvim/api/win_config.c
index 543c7b8113..3a9986a7d1 100644
--- a/src/nvim/api/win_config.c
+++ b/src/nvim/api/win_config.c
@@ -12,6 +12,7 @@
 #include "nvim/ascii_defs.h"
 #include "nvim/autocmd.h"
 #include "nvim/autocmd_defs.h"
+#include "nvim/buffer.h"
 #include "nvim/buffer_defs.h"
 #include "nvim/decoration.h"
 #include "nvim/decoration_defs.h"
@@ -198,9 +199,8 @@
 ///   - footer_pos: Footer position. Must be set with `footer` option.
 ///     Value can be one of "left", "center", or "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.
+///   - noautocmd: If true then all autocommands are blocked for the duration of
+///     the call.
 ///   - fixed: If true when anchor is NW or SW, the float window
 ///            would be kept fixed even if the window would be truncated.
 ///   - hide: If true the floating window will be hidden.
@@ -224,25 +224,33 @@ Window nvim_open_win(Buffer buffer, Boolean enter, Dict(win_config) *config, Err
   }
 
   WinConfig fconfig = WIN_CONFIG_INIT;
-  if (!parse_float_config(config, &fconfig, false, true, err)) {
+  if (!parse_win_config(NULL, config, &fconfig, false, err)) {
     return 0;
   }
 
   bool is_split = HAS_KEY_X(config, split) || HAS_KEY_X(config, vertical);
+  Window rv = 0;
+  if (fconfig.noautocmd) {
+    block_autocmds();
+  }
 
   win_T *wp = NULL;
   tabpage_T *tp = curtab;
+  win_T *parent = NULL;
+  if (config->win != -1) {
+    parent = find_window_by_handle(fconfig.window, err);
+    if (!parent) {
+      // find_window_by_handle has already set the error
+      goto cleanup;
+    } else if (is_split && parent->w_floating) {
+      api_set_error(err, kErrorTypeException, "Cannot split a floating window");
+      goto cleanup;
+    }
+    tp = win_find_tabpage(parent);
+  }
   if (is_split) {
-    win_T *parent = NULL;
-    if (config->win != -1) {
-      parent = find_window_by_handle(fconfig.window, err);
-      if (!parent) {
-        // find_window_by_handle has already set the error
-        return 0;
-      } else if (parent->w_floating) {
-        api_set_error(err, kErrorTypeException, "Cannot split a floating window");
-        return 0;
-      }
+    if (!check_split_disallowed_err(parent ? parent : curwin, err)) {
+      goto cleanup;  // error already set
     }
 
     if (HAS_KEY_X(config, vertical) && !HAS_KEY_X(config, split)) {
@@ -254,18 +262,20 @@ Window nvim_open_win(Buffer buffer, Boolean enter, Dict(win_config) *config, Err
     }
     int flags = win_split_flags(fconfig.split, parent == NULL) | WSP_NOENTER;
 
-    if (parent == NULL) {
-      wp = win_split_ins(0, flags, NULL, 0);
-    } else {
-      tp = win_find_tabpage(parent);
-      switchwin_T switchwin;
-      // `parent` is valid in `tp`, so switch_win should not fail.
-      const int result = switch_win(&switchwin, parent, tp, true);
-      (void)result;
-      assert(result == OK);
-      wp = win_split_ins(0, flags, NULL, 0);
-      restore_win(&switchwin, true);
-    }
+    TRY_WRAP(err, {
+      int size = (flags & WSP_VERT) ? fconfig.width : fconfig.height;
+      if (parent == NULL || parent == curwin) {
+        wp = win_split_ins(size, flags, NULL, 0, NULL);
+      } else {
+        switchwin_T switchwin;
+        // `parent` is valid in `tp`, so switch_win should not fail.
+        const int result = switch_win(&switchwin, parent, tp, true);
+        assert(result == OK);
+        (void)result;
+        wp = win_split_ins(size, flags, NULL, 0, NULL);
+        restore_win(&switchwin, true);
+      }
+    });
     if (wp) {
       wp->w_config = fconfig;
     }
@@ -273,30 +283,64 @@ Window nvim_open_win(Buffer buffer, Boolean enter, Dict(win_config) *config, Err
     wp = win_new_float(NULL, false, fconfig, err);
   }
   if (!wp) {
-    api_set_error(err, kErrorTypeException, "Failed to create window");
-    return 0;
+    if (!ERROR_SET(err)) {
+      api_set_error(err, kErrorTypeException, "Failed to create window");
+    }
+    goto cleanup;
   }
-  switchwin_T switchwin;
-  if (switch_win_noblock(&switchwin, wp, tp, true) == OK) {
-    apply_autocmds(EVENT_WINNEW, NULL, NULL, false, curbuf);
+
+  // Autocommands may close `wp` or move it to another tabpage, so update and check `tp` after each
+  // event. In each case, `wp` should already be valid in `tp`, so switch_win should not fail.
+  // Also, autocommands may free the `buf` to switch to, so store a bufref to check.
+  bufref_T bufref;
+  set_bufref(&bufref, buf);
+  if (!fconfig.noautocmd) {
+    switchwin_T switchwin;
+    const int result = switch_win_noblock(&switchwin, wp, tp, true);
+    assert(result == OK);
+    (void)result;
+    if (apply_autocmds(EVENT_WINNEW, NULL, NULL, false, curbuf)) {
+      tp = win_find_tabpage(wp);
+    }
+    restore_win_noblock(&switchwin, true);
   }
-  restore_win_noblock(&switchwin, true);
-  if (enter) {
+  if (tp && enter) {
     goto_tabpage_win(tp, wp);
+    tp = win_find_tabpage(wp);
   }
-  if (win_valid_any_tab(wp) && buf != wp->w_buffer) {
-    win_set_buf(wp, buf, !enter || fconfig.noautocmd, err);
+  if (tp && bufref_valid(&bufref) && buf != wp->w_buffer) {
+    // win_set_buf temporarily makes `wp` the curwin to set the buffer.
+    // If not entering `wp`, block Enter and Leave events. (cringe)
+    const bool au_no_enter_leave = curwin != wp && !fconfig.noautocmd;
+    if (au_no_enter_leave) {
+      autocmd_no_enter++;
+      autocmd_no_leave++;
+    }
+    win_set_buf(wp, buf, err);
+    if (!fconfig.noautocmd) {
+      tp = win_find_tabpage(wp);
+    }
+    if (au_no_enter_leave) {
+      autocmd_no_enter--;
+      autocmd_no_leave--;
+    }
   }
-  if (!win_valid_any_tab(wp)) {
+  if (!tp) {
     api_set_error(err, kErrorTypeException, "Window was closed immediately");
-    return 0;
+    goto cleanup;
   }
 
   if (fconfig.style == kWinStyleMinimal) {
     win_set_minimal_style(wp);
     didset_window_options(wp, true);
   }
-  return wp->handle;
+  rv = wp->handle;
+
+cleanup:
+  if (fconfig.noautocmd) {
+    unblock_autocmds();
+  }
+  return rv;
 #undef HAS_KEY_X
 }
 
@@ -330,11 +374,11 @@ static int win_split_flags(WinSplit split, bool toplevel)
   return flags;
 }
 
-/// Configures window layout. Currently only for floating and external windows
-/// (including changing a split window to those layouts).
+/// Configures window layout. Cannot be used to move the last window in a
+/// tabpage to a different one.
 ///
-/// When reconfiguring a floating window, absent option keys will not be
-/// changed.  `row`/`col` and `relative` must be reconfigured together.
+/// When reconfiguring a window, absent option keys will not be changed.
+/// `row`/`col` and `relative` must be reconfigured together.
 ///
 /// @see |nvim_open_win()|
 ///
@@ -350,6 +394,7 @@ void nvim_win_set_config(Window window, Dict(win_config) *config, Error *err)
   if (!win) {
     return;
   }
+
   tabpage_T *win_tp = win_find_tabpage(win);
   bool was_split = !win->w_floating;
   bool has_split = HAS_KEY_X(config, split);
@@ -361,26 +406,31 @@ void nvim_win_set_config(Window window, Dict(win_config) *config, Error *err)
                   && !(HAS_KEY_X(config, external) ? config->external : fconfig.external)
                   && (has_split || has_vertical || was_split);
 
-  if (!parse_float_config(config, &fconfig, !was_split || to_split, false, err)) {
+  if (!parse_win_config(win, config, &fconfig, !was_split || to_split, err)) {
     return;
   }
+  win_T *parent = NULL;
+  if (config->win != -1) {
+    parent = find_window_by_handle(fconfig.window, err);
+    if (!parent) {
+      return;
+    } else if (to_split && parent->w_floating) {
+      api_set_error(err, kErrorTypeException, "Cannot split a floating window");
+      return;
+    }
+
+    // Prevent autocmd window from being moved into another tabpage
+    if (is_aucmd_win(win) && win_find_tabpage(win) != win_find_tabpage(parent)) {
+      api_set_error(err, kErrorTypeException, "Cannot move autocmd win to another tabpage");
+      return;
+    }
+  }
   if (was_split && !to_split) {
     if (!win_new_float(win, false, fconfig, err)) {
       return;
     }
     redraw_later(win, UPD_NOT_VALID);
   } else if (to_split) {
-    win_T *parent = NULL;
-    if (config->win != -1) {
-      parent = find_window_by_handle(fconfig.window, err);
-      if (!parent) {
-        return;
-      } else if (parent->w_floating) {
-        api_set_error(err, kErrorTypeException, "Cannot split a floating window");
-        return;
-      }
-    }
-
     WinSplit old_split = win_split_dir(win);
     if (has_vertical && !has_split) {
       if (config->vertical) {
@@ -413,17 +463,59 @@ void nvim_win_set_config(Window window, Dict(win_config) *config, Error *err)
       return;
     }
 
-    if (was_split) {
-      win_T *new_curwin = NULL;
+    if (!check_split_disallowed_err(win, err)) {
+      return;  // error already set
+    }
+    // Can't move the cmdwin or its old curwin to a different tabpage.
+    if ((win == cmdwin_win || win == cmdwin_old_curwin) && parent != NULL
+        && win_find_tabpage(parent) != win_tp) {
+      api_set_error(err, kErrorTypeException, "%s", e_cmdwin);
+      return;
+    }
+
+    bool to_split_ok = false;
+    // If we are moving curwin to another tabpage, switch windows *before* we remove it from the
+    // window list or remove its frame (if non-floating), so it's valid for autocommands.
+    const bool curwin_moving_tp
+      = win == curwin && parent != NULL && win_tp != win_find_tabpage(parent);
+    if (curwin_moving_tp) {
+      if (was_split) {
+        int dir;
+        win_goto(winframe_find_altwin(win, &dir, NULL, NULL));
+      } else {
+        win_goto(win_float_find_altwin(win, NULL));
+      }
+
+      // Autocommands may have been a real nuisance and messed things up...
+      if (curwin == win) {
+        api_set_error(err, kErrorTypeException, "Failed to switch away from window %d",
+                      win->handle);
+        return;
+      }
+      win_tp = win_find_tabpage(win);
+      if (!win_tp || !win_valid_any_tab(parent)) {
+        api_set_error(err, kErrorTypeException, "Windows to split were closed");
+        goto restore_curwin;
+      }
+      if (was_split == win->w_floating || parent->w_floating) {
+        api_set_error(err, kErrorTypeException, "Floating state of windows to split changed");
+        goto restore_curwin;
+      }
+    }
 
+    int dir = 0;
+    frame_T *unflat_altfr = NULL;
+    win_T *altwin = NULL;
+
+    if (was_split) {
       // If the window is the last in the tabpage or `fconfig.win` is
       // a handle to itself, we can't split it.
       if (win->w_frame->fr_parent == NULL) {
         // FIXME(willothy): if the window is the last in the tabpage but there is another tabpage
         // and the target window is in that other tabpage, should we move the window to that
         // tabpage and close the previous one, or just error?
-        api_set_error(err, kErrorTypeValidation, "Cannot move last window");
-        return;
+        api_set_error(err, kErrorTypeException, "Cannot move last window");
+        goto restore_curwin;
       } else if (parent != NULL && parent->handle == win->handle) {
         int n_frames = 0;
         for (frame_T *fr = win->w_frame->fr_parent->fr_child; fr != NULL; fr = fr->fr_next) {
@@ -459,83 +551,82 @@ void nvim_win_set_config(Window window, Dict(win_config) *config, Error *err)
           }
           // If the frame doesn't have a parent, the old frame
           // was the root frame and we need to create a top-level split.
-          int dir;
-          new_curwin = winframe_remove(win, &dir, win_tp == curtab ? NULL : win_tp);
+          altwin = winframe_remove(win, &dir, win_tp == curtab ? NULL : win_tp, &unflat_altfr);
         } else if (n_frames == 2) {
           // There are two windows in the frame, we can just rotate it.
-          int dir;
-          neighbor = winframe_remove(win, &dir, win_tp == curtab ? NULL : win_tp);
-          new_curwin = neighbor;
+          altwin = winframe_remove(win, &dir, win_tp == curtab ? NULL : win_tp, &unflat_altfr);
+          neighbor = altwin;
         } else {
           // There is only one window in the frame, we can't split it.
-          api_set_error(err, kErrorTypeValidation, "Cannot split window into itself");
-          return;
+          api_set_error(err, kErrorTypeException, "Cannot split window into itself");
+          goto restore_curwin;
         }
-        // Set the parent to whatever the correct
-        // neighbor window was determined to be.
+        // Set the parent to whatever the correct neighbor window was determined to be.
         parent = neighbor;
       } else {
-        int dir;
-        new_curwin = winframe_remove(win, &dir, win_tp == curtab ? NULL : win_tp);
-      }
-      // move to neighboring window if we're moving the current window to a new tabpage
-      if (curwin == win && parent != NULL && new_curwin != NULL
-          && win_tp != win_find_tabpage(parent)) {
-        win_enter(new_curwin, true);
+        altwin = winframe_remove(win, &dir, win_tp == curtab ? NULL : win_tp, &unflat_altfr);
       }
-      win_remove(win, win_tp == curtab ? NULL : win_tp);
     } else {
-      win_remove(win, win_tp == curtab ? NULL : win_tp);
-      ui_comp_remove_grid(&win->w_grid_alloc);
-      if (win->w_config.external) {
-        for (tabpage_T *tp = first_tabpage; tp != NULL; tp = tp->tp_next) {
-          if (tp == curtab) {
-            continue;
-          }
-          if (tp->tp_curwin == win) {
-            tp->tp_curwin = tp->tp_firstwin;
-          }
-        }
-      }
-      win->w_pos_changed = true;
+      altwin = win_float_find_altwin(win, win_tp == curtab ? NULL : win_tp);
     }
 
-    int flags = win_split_flags(fconfig.split, parent == NULL);
+    win_remove(win, win_tp == curtab ? NULL : win_tp);
+    if (win_tp == curtab) {
+      last_status(false);  // may need to remove last status line
+      win_comp_pos();  // recompute window positions
+    }
 
-    if (parent == NULL) {
-      if (!win_split_ins(0, flags, win, 0)) {
-        // TODO(willothy): What should this error message say?
-        api_set_error(err, kErrorTypeException, "Failed to split window");
-        return;
-      }
-    } else {
-      win_execute_T args;
+    int flags = win_split_flags(fconfig.split, parent == NULL) | WSP_NOENTER;
+    tabpage_T *const parent_tp = parent ? win_find_tabpage(parent) : curtab;
 
-      tabpage_T *tp = win_find_tabpage(parent);
-      if (!win_execute_before(&args, parent, tp)) {
-        // TODO(willothy): how should we handle this / what should the message be?
-        api_set_error(err, kErrorTypeException, "Failed to switch to tabpage %d", tp->handle);
-        win_execute_after(&args);
-        return;
+    TRY_WRAP(err, {
+      const bool need_switch = parent != NULL && parent != curwin;
+      switchwin_T switchwin;
+      if (need_switch) {
+        // `parent` is valid in its tabpage, so switch_win should not fail.
+        const int result = switch_win(&switchwin, parent, parent_tp, true);
+        (void)result;
+        assert(result == OK);
       }
-      // This should return the same ptr to `win`, but we check for
-      // NULL to detect errors.
-      win_T *res = win_split_ins(0, flags, win, 0);
-      win_execute_after(&args);
-      if (!res) {
-        // TODO(willothy): What should this error message say?
-        api_set_error(err, kErrorTypeException, "Failed to split window");
-        return;
+      to_split_ok = win_split_ins(0, flags, win, 0, unflat_altfr) != NULL;
+      if (!to_split_ok) {
+        // Restore `win` to the window list now, so it's valid for restore_win (if used).
+        win_append(win->w_prev, win, win_tp == curtab ? NULL : win_tp);
+      }
+      if (need_switch) {
+        restore_win(&switchwin, true);
+      }
+    });
+    if (!to_split_ok) {
+      if (was_split) {
+        // win_split_ins doesn't change sizes or layout if it fails to insert an existing window, so
+        // just undo winframe_remove.
+        winframe_restore(win, dir, unflat_altfr);
+      }
+      if (!ERROR_SET(err)) {
+        api_set_error(err, kErrorTypeException, "Failed to move window %d into split", win->handle);
+      }
+
+restore_curwin:
+      // If `win` was the original curwin, and autocommands didn't move it outside of curtab, be a
+      // good citizen and try to return to it.
+      if (curwin_moving_tp && win_valid(win)) {
+        win_goto(win);
       }
+      return;
+    }
+
+    // If `win` moved tabpages and was the curwin of its old one, select a new curwin for it.
+    if (win_tp != parent_tp && win_tp->tp_curwin == win) {
+      win_tp->tp_curwin = altwin;
     }
+
     if (HAS_KEY_X(config, width)) {
       win_setwidth_win(fconfig.width, win);
     }
     if (HAS_KEY_X(config, height)) {
       win_setheight_win(fconfig.height, win);
     }
-    redraw_later(win, UPD_NOT_VALID);
-    return;
   } else {
     win_config_float(win, fconfig);
     win->w_pos_changed = true;
@@ -947,8 +1038,19 @@ static void parse_border_style(Object style, WinConfig *fconfig, Error *err)
   }
 }
 
-static bool parse_float_config(Dict(win_config) *config, WinConfig *fconfig, bool reconf,
-                               bool new_win, Error *err)
+static void generate_api_error(win_T *wp, const char *attribute, Error *err)
+{
+  if (wp->w_floating) {
+    api_set_error(err, kErrorTypeValidation,
+                  "Missing 'relative' field when reconfiguring floating window %d",
+                  wp->handle);
+  } else {
+    api_set_error(err, kErrorTypeValidation, "non-float cannot have '%s'", attribute);
+  }
+}
+
+static bool parse_win_config(win_T *wp, Dict(win_config) *config, WinConfig *fconfig, bool reconf,
+                             Error *err)
 {
 #define HAS_KEY_X(d, key) HAS_KEY(d, win_config, key)
   bool has_relative = false, relative_is_win = false, is_split = false;
@@ -973,7 +1075,7 @@ static bool parse_float_config(Dict(win_config) *config, WinConfig *fconfig, boo
   } else if (!config->external) {
     if (HAS_KEY_X(config, vertical) || HAS_KEY_X(config, split)) {
       is_split = true;
-    } else if (new_win) {
+    } else if (wp == NULL) {  // new win
       api_set_error(err, kErrorTypeValidation,
                     "Must specify 'relative' or 'external' when creating a float");
       return false;
@@ -1007,7 +1109,7 @@ static bool parse_float_config(Dict(win_config) *config, WinConfig *fconfig, boo
 
   if (HAS_KEY_X(config, row)) {
     if (!has_relative || is_split) {
-      api_set_error(err, kErrorTypeValidation, "non-float cannot have 'row'");
+      generate_api_error(wp, "row", err);
       return false;
     }
     fconfig->row = config->row;
@@ -1015,7 +1117,7 @@ static bool parse_float_config(Dict(win_config) *config, WinConfig *fconfig, boo
 
   if (HAS_KEY_X(config, col)) {
     if (!has_relative || is_split) {
-      api_set_error(err, kErrorTypeValidation, "non-float cannot have 'col'");
+      generate_api_error(wp, "col", err);
       return false;
     }
     fconfig->col = config->col;
@@ -1023,7 +1125,7 @@ static bool parse_float_config(Dict(win_config) *config, WinConfig *fconfig, boo
 
   if (HAS_KEY_X(config, bufpos)) {
     if (!has_relative || is_split) {
-      api_set_error(err, kErrorTypeValidation, "non-float cannot have 'bufpos'");
+      generate_api_error(wp, "bufpos", err);
       return false;
     } else {
       if (!parse_float_bufpos(config->bufpos, &fconfig->bufpos)) {
@@ -1065,17 +1167,32 @@ static bool parse_float_config(Dict(win_config) *config, WinConfig *fconfig, boo
   }
 
   if (relative_is_win || is_split) {
+    if (reconf && relative_is_win) {
+      win_T *target_win = find_window_by_handle(config->win, err);
+      if (!target_win) {
+        return false;
+      }
+
+      if (target_win == wp) {
+        api_set_error(err, kErrorTypeException, "floating window cannot be relative to itself");
+        return false;
+      }
+    }
     fconfig->window = curwin->handle;
     if (HAS_KEY_X(config, win)) {
       if (config->win > 0) {
         fconfig->window = config->win;
       }
     }
-  } else if (has_relative) {
-    if (HAS_KEY_X(config, win)) {
+  } else if (HAS_KEY_X(config, win)) {
+    if (has_relative) {
       api_set_error(err, kErrorTypeValidation,
                     "'win' key is only valid with relative='win' and relative=''");
       return false;
+    } else if (!is_split) {
+      api_set_error(err, kErrorTypeValidation,
+                    "non-float with 'win' requires at least 'split' or 'vertical'");
+      return false;
     }
   }
 
@@ -1186,8 +1303,8 @@ static bool parse_float_config(Dict(win_config) *config, WinConfig *fconfig, boo
   }
 
   if (HAS_KEY_X(config, noautocmd)) {
-    if (!new_win) {
-      api_set_error(err, kErrorTypeValidation, "Invalid key: 'noautocmd'");
+    if (wp) {
+      api_set_error(err, kErrorTypeValidation, "'noautocmd' cannot be used with existing windows");
       return false;
     }
     fconfig->noautocmd = config->noautocmd;
diff --git a/src/nvim/api/window.c b/src/nvim/api/window.c
index ed51eedf1b..54a19513db 100644
--- a/src/nvim/api/window.c
+++ b/src/nvim/api/window.c
@@ -61,11 +61,17 @@ void nvim_win_set_buf(Window window, Buffer buffer, Error *err)
   if (!win || !buf) {
     return;
   }
+
+  if (win->w_p_wfb) {
+    api_set_error(err, kErrorTypeException, "%s", e_winfixbuf_cannot_go_to_buffer);
+    return;
+  }
+
   if (win == cmdwin_win || win == cmdwin_old_curwin || buf == cmdwin_buf) {
     api_set_error(err, kErrorTypeException, "%s", e_cmdwin);
     return;
   }
-  win_set_buf(win, buf, false, err);
+  win_set_buf(win, buf, err);
 }
 
 /// Gets the (1,0)-indexed, buffer-relative cursor position for a given window
@@ -132,7 +138,7 @@ void nvim_win_set_cursor(Window window, ArrayOf(Integer, 2) pos, Error *err)
   win->w_cursor.col = (colnr_T)col;
   win->w_cursor.coladd = 0;
   // When column is out of range silently correct it.
-  check_cursor_col_win(win);
+  check_cursor_col(win);
 
   // Make sure we stick in this column.
   win->w_set_curswant = true;
@@ -142,7 +148,7 @@ void nvim_win_set_cursor(Window window, ArrayOf(Integer, 2) pos, Error *err)
   switchwin_T switchwin;
   switch_win(&switchwin, win, NULL, true);
   update_topline(curwin);
-  validate_cursor();
+  validate_cursor(curwin);
   restore_win(&switchwin, true);
 
   redraw_later(win, UPD_VALID);