Merge pull request #19409 from bfredl/uiunpack

perf(ui): some ui_client fixes/optimizations before externalized TUI

19 files changed, 342 insertions, 161 deletions

diff --git a/scripts/gen_vimdoc.py b/scripts/gen_vimdoc.py
index 74b35b4e9b..c17742ddaf 100755
--- a/scripts/gen_vimdoc.py
+++ b/scripts/gen_vimdoc.py
@@ -949,7 +949,8 @@ def fmt_doxygen_xml_as_vimhelp(filename, target):
 
         func_doc = "\n".join(split_lines)
 
-        if name.startswith(CONFIG[target]['fn_name_prefix']):
+        if (name.startswith(CONFIG[target]['fn_name_prefix'])
+           and name != "nvim_error_event"):
             fns_txt[name] = func_doc
 
     return ('\n\n'.join(list(fns_txt.values())),
diff --git a/src/nvim/api/private/defs.h b/src/nvim/api/private/defs.h
index b1e0dd364c..9c7e59e4b3 100644
--- a/src/nvim/api/private/defs.h
+++ b/src/nvim/api/private/defs.h
@@ -36,6 +36,7 @@ typedef enum {
   kMessageTypeRequest = 0,
   kMessageTypeResponse = 1,
   kMessageTypeNotification = 2,
+  kMessageTypeRedrawEvent = 3,
 } MessageType;
 
 /// Mask for all internal calls
diff --git a/src/nvim/api/private/helpers.h b/src/nvim/api/private/helpers.h
index a4348d8b44..224ce41aae 100644
--- a/src/nvim/api/private/helpers.h
+++ b/src/nvim/api/private/helpers.h
@@ -86,6 +86,12 @@
   name.capacity = maxsize; \
   name.items = name##__items; \
 
+#define MAXSIZE_TEMP_DICT(name, maxsize) \
+  Dictionary name = ARRAY_DICT_INIT; \
+  KeyValuePair name##__items[maxsize]; \
+  name.capacity = maxsize; \
+  name.items = name##__items; \
+
 #define cbuf_as_string(d, s) ((String) { .data = d, .size = s })
 
 #define STATIC_CSTR_AS_STRING(s) ((String) { .data = s, .size = sizeof(s) - 1 })
diff --git a/src/nvim/api/ui.c b/src/nvim/api/ui.c
index 54ce838b9b..aa7bed1132 100644
--- a/src/nvim/api/ui.c
+++ b/src/nvim/api/ui.c
@@ -748,8 +748,10 @@ 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));
-  ADD_C(args, DICTIONARY_OBJ(hlattrs2dict(rgb_attrs, true)));
-  ADD_C(args, DICTIONARY_OBJ(hlattrs2dict(cterm_attrs, false)));
+  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)));
 
   if (ui->ui_ext[kUIHlState]) {
     ADD_C(args, ARRAY_OBJ(info));
@@ -758,9 +760,6 @@ static void remote_ui_hl_attr_define(UI *ui, Integer id, HlAttrs rgb_attrs, HlAt
   }
 
   push_call(ui, "hl_attr_define", args);
-  // TODO(bfredl): could be elided
-  api_free_dictionary(kv_A(args, 1).data.dictionary);
-  api_free_dictionary(kv_A(args, 2).data.dictionary);
 }
 
 static void remote_ui_highlight_set(UI *ui, int id)
@@ -772,11 +771,9 @@ static void remote_ui_highlight_set(UI *ui, int id)
     return;
   }
   data->hl_id = id;
-  Dictionary hl = hlattrs2dict(syn_attr2entry(id), ui->rgb);
-
-  ADD_C(args, DICTIONARY_OBJ(hl));
+  MAXSIZE_TEMP_DICT(dict, 16);
+  ADD_C(args, DICTIONARY_OBJ(hlattrs2dict(&dict, syn_attr2entry(id), ui->rgb)));
   push_call(ui, "highlight_set", args);
-  api_free_dictionary(kv_A(args, 0).data.dictionary);
 }
 
 /// "true" cursor used only for input focus
@@ -963,7 +960,7 @@ static Array translate_contents(UI *ui, Array contents)
     Array new_item = ARRAY_DICT_INIT;
     int attr = (int)item.items[0].data.integer;
     if (attr) {
-      Dictionary rgb_attrs = hlattrs2dict(syn_attr2entry(attr), ui->rgb);
+      Dictionary rgb_attrs = hlattrs2dict(NULL, syn_attr2entry(attr), ui->rgb);
       ADD(new_item, DICTIONARY_OBJ(rgb_attrs));
     } else {
       ADD(new_item, DICTIONARY_OBJ((Dictionary)ARRAY_DICT_INIT));
diff --git a/src/nvim/api/vim.c b/src/nvim/api/vim.c
index 56516b2ac7..5d941890db 100644
--- a/src/nvim/api/vim.c
+++ b/src/nvim/api/vim.c
@@ -2256,3 +2256,11 @@ Dictionary nvim_eval_statusline(String str, Dict(eval_statusline) *opts, Error *
 
   return result;
 }
+
+void nvim_error_event(uint64_t channel_id, Integer lvl, String data)
+  FUNC_API_REMOTE_ONLY
+{
+  // TODO(bfredl): consider printing message to user, as will be relevant
+  // if we fork nvim processes as async workers
+  ELOG("async error on channel %" PRId64 ": %s", channel_id, data.size ? data.data : "");
+}
diff --git a/src/nvim/generators/gen_api_dispatch.lua b/src/nvim/generators/gen_api_dispatch.lua
index 4cf282770d..b167767f7a 100644
--- a/src/nvim/generators/gen_api_dispatch.lua
+++ b/src/nvim/generators/gen_api_dispatch.lua
@@ -91,7 +91,7 @@ local deprecated_aliases = require("api.dispatch_deprecated")
 for _,f in ipairs(shallowcopy(functions)) do
   local ismethod = false
   if startswith(f.name, "nvim_") then
-    if startswith(f.name, "nvim__") then
+    if startswith(f.name, "nvim__") or f.name == "nvim_error_event" then
       f.since = -1
     elseif f.since == nil then
       print("Function "..f.name.." lacks since field.\n")
@@ -149,7 +149,7 @@ local exported_attributes = {'name', 'return_type', 'method',
                              'since', 'deprecated_since'}
 local exported_functions = {}
 for _,f in ipairs(functions) do
-  if not startswith(f.name, "nvim__") then
+  if not (startswith(f.name, "nvim__") or f.name == "nvim_error_event") then
     local f_exported = {}
     for _,attr in ipairs(exported_attributes) do
       f_exported[attr] = f[attr]
diff --git a/src/nvim/grid_defs.h b/src/nvim/grid_defs.h
index 1571340849..9252b8a371 100644
--- a/src/nvim/grid_defs.h
+++ b/src/nvim/grid_defs.h
@@ -128,4 +128,13 @@ typedef struct {
   const char *start;       ///< Location where region starts.
 } StlClickRecord;
 
+typedef struct {
+  int args[3];
+  int icell;
+  int ncells;
+  int coloff;
+  int cur_attr;
+  int clear_width;
+} GridLineEvent;
+
 #endif  // NVIM_GRID_DEFS_H
diff --git a/src/nvim/highlight.c b/src/nvim/highlight.c
index 0f20eb1905..83d819d3ec 100644
--- a/src/nvim/highlight.c
+++ b/src/nvim/highlight.c
@@ -719,93 +719,107 @@ Dictionary hl_get_attr_by_id(Integer attr_id, Boolean rgb, Error *err)
     return dic;
   }
 
-  return hlattrs2dict(syn_attr2entry((int)attr_id), rgb);
+  return hlattrs2dict(NULL, syn_attr2entry((int)attr_id), rgb);
 }
 
 /// Converts an HlAttrs into Dictionary
 ///
+/// @param[out] hl optional pre-allocated dictionary for return value
+///                if present, must be allocated with at least 16 elements!
 /// @param[in] aep data to convert
 /// @param use_rgb use 'gui*' settings if true, else resorts to 'cterm*'
-Dictionary hlattrs2dict(HlAttrs ae, bool use_rgb)
+Dictionary hlattrs2dict(Dictionary *hl_alloc, HlAttrs ae, bool use_rgb)
 {
-  Dictionary hl = ARRAY_DICT_INIT;
   int mask  = use_rgb ? ae.rgb_ae_attr : ae.cterm_ae_attr;
+  Dictionary hl = ARRAY_DICT_INIT;
+  if (hl_alloc) {
+    hl = *hl_alloc;
+  } else {
+    kv_ensure_space(hl, 16);
+  }
 
   if (mask & HL_BOLD) {
-    PUT(hl, "bold", BOOLEAN_OBJ(true));
+    PUT_C(hl, "bold", BOOLEAN_OBJ(true));
   }
 
   if (mask & HL_STANDOUT) {
-    PUT(hl, "standout", BOOLEAN_OBJ(true));
+    PUT_C(hl, "standout", BOOLEAN_OBJ(true));
   }
 
   if (mask & HL_UNDERLINE) {
-    PUT(hl, "underline", BOOLEAN_OBJ(true));
+    PUT_C(hl, "underline", BOOLEAN_OBJ(true));
   }
 
   if (mask & HL_UNDERCURL) {
-    PUT(hl, "undercurl", BOOLEAN_OBJ(true));
+    PUT_C(hl, "undercurl", BOOLEAN_OBJ(true));
   }
 
   if (mask & HL_UNDERDOUBLE) {
-    PUT(hl, "underdouble", BOOLEAN_OBJ(true));
+    PUT_C(hl, "underdouble", BOOLEAN_OBJ(true));
   }
 
   if (mask & HL_UNDERDOTTED) {
-    PUT(hl, "underdotted", BOOLEAN_OBJ(true));
+    PUT_C(hl, "underdotted", BOOLEAN_OBJ(true));
   }
 
   if (mask & HL_UNDERDASHED) {
-    PUT(hl, "underdashed", BOOLEAN_OBJ(true));
+    PUT_C(hl, "underdashed", BOOLEAN_OBJ(true));
   }
 
   if (mask & HL_ITALIC) {
-    PUT(hl, "italic", BOOLEAN_OBJ(true));
+    PUT_C(hl, "italic", BOOLEAN_OBJ(true));
   }
 
   if (mask & HL_INVERSE) {
-    PUT(hl, "reverse", BOOLEAN_OBJ(true));
+    PUT_C(hl, "reverse", BOOLEAN_OBJ(true));
   }
 
   if (mask & HL_STRIKETHROUGH) {
-    PUT(hl, "strikethrough", BOOLEAN_OBJ(true));
+    PUT_C(hl, "strikethrough", BOOLEAN_OBJ(true));
   }
 
   if (use_rgb) {
     if (mask & HL_FG_INDEXED) {
-      PUT(hl, "fg_indexed", BOOLEAN_OBJ(true));
+      PUT_C(hl, "fg_indexed", BOOLEAN_OBJ(true));
     }
 
     if (mask & HL_BG_INDEXED) {
-      PUT(hl, "bg_indexed", BOOLEAN_OBJ(true));
+      PUT_C(hl, "bg_indexed", BOOLEAN_OBJ(true));
     }
 
     if (ae.rgb_fg_color != -1) {
-      PUT(hl, "foreground", INTEGER_OBJ(ae.rgb_fg_color));
+      PUT_C(hl, "foreground", INTEGER_OBJ(ae.rgb_fg_color));
     }
 
     if (ae.rgb_bg_color != -1) {
-      PUT(hl, "background", INTEGER_OBJ(ae.rgb_bg_color));
+      PUT_C(hl, "background", INTEGER_OBJ(ae.rgb_bg_color));
     }
 
     if (ae.rgb_sp_color != -1) {
-      PUT(hl, "special", INTEGER_OBJ(ae.rgb_sp_color));
+      PUT_C(hl, "special", INTEGER_OBJ(ae.rgb_sp_color));
     }
   } else {
     if (ae.cterm_fg_color != 0) {
-      PUT(hl, "foreground", INTEGER_OBJ(ae.cterm_fg_color - 1));
+      PUT_C(hl, "foreground", INTEGER_OBJ(ae.cterm_fg_color - 1));
     }
 
     if (ae.cterm_bg_color != 0) {
-      PUT(hl, "background", INTEGER_OBJ(ae.cterm_bg_color - 1));
+      PUT_C(hl, "background", INTEGER_OBJ(ae.cterm_bg_color - 1));
     }
   }
 
   if (ae.hl_blend > -1) {
-    PUT(hl, "blend", INTEGER_OBJ(ae.hl_blend));
+    PUT_C(hl, "blend", INTEGER_OBJ(ae.hl_blend));
   }
 
-  return hl;
+  if (hl_alloc) {
+    *hl_alloc = hl;
+    return hl;
+  } else {
+    Dictionary allocated = copy_dictionary(hl);
+    kv_destroy(hl);
+    return allocated;
+  }
 }
 
 HlAttrs dict2hlattrs(Dict(highlight) *dict, bool use_rgb, int *link_id, Error *err)
diff --git a/src/nvim/highlight_group.c b/src/nvim/highlight_group.c
index d958b7b344..5027454222 100644
--- a/src/nvim/highlight_group.c
+++ b/src/nvim/highlight_group.c
@@ -1409,7 +1409,7 @@ Dictionary get_global_hl_defs(void)
     Dictionary attrs = ARRAY_DICT_INIT;
     HlGroup *h = &hl_table[i - 1];
     if (h->sg_attr > 0) {
-      attrs = hlattrs2dict(syn_attr2entry(h->sg_attr), true);
+      attrs = hlattrs2dict(NULL, syn_attr2entry(h->sg_attr), true);
     } else if (h->sg_link > 0) {
       const char *link = (const char *)hl_table[h->sg_link - 1].sg_name;
       PUT(attrs, "link", STRING_OBJ(cstr_to_string(link)));
diff --git a/src/nvim/main.c b/src/nvim/main.c
index b06b9630e2..c9403d9f19 100644
--- a/src/nvim/main.c
+++ b/src/nvim/main.c
@@ -202,7 +202,6 @@ void early_init(mparm_T *paramp)
   set_lang_var();               // set v:lang and v:ctype
 
   init_signs();
-  ui_comp_syn_init();
 }
 
 #ifdef MAKE_LIB
@@ -320,6 +319,7 @@ int main(int argc, char **argv)
   no_wait_return = true;
 
   init_highlight(true, false);  // Default highlight groups.
+  ui_comp_syn_init();
   TIME_MSG("init highlight");
 
   // Set the break level after the terminal is initialized.
diff --git a/src/nvim/msgpack_rpc/channel.c b/src/nvim/msgpack_rpc/channel.c
index de01443313..1ca68979f4 100644
--- a/src/nvim/msgpack_rpc/channel.c
+++ b/src/nvim/msgpack_rpc/channel.c
@@ -239,7 +239,14 @@ static void parse_msgpack(Channel *channel)
 {
   Unpacker *p = channel->rpc.unpacker;
   while (unpacker_advance(p)) {
-    if (p->type == kMessageTypeResponse) {
+    if (p->type == kMessageTypeRedrawEvent) {
+      if (p->grid_line_event) {
+        ui_client_event_raw_line(p->grid_line_event);
+      } else if (p->ui_handler.fn != NULL && p->result.type == kObjectTypeArray) {
+        p->ui_handler.fn(p->result.data.array);
+        arena_mem_free(arena_finish(&p->arena), &p->reuse_blk);
+      }
+    } else if (p->type == kMessageTypeResponse) {
       ChannelCallFrame *frame = kv_last(channel->rpc.call_stack);
       if (p->request_id != frame->request_id) {
         char buf[256];
diff --git a/src/nvim/msgpack_rpc/unpacker.c b/src/nvim/msgpack_rpc/unpacker.c
index 26c1843026..d73557ec11 100644
--- a/src/nvim/msgpack_rpc/unpacker.c
+++ b/src/nvim/msgpack_rpc/unpacker.c
@@ -6,6 +6,7 @@
 #include "nvim/memory.h"
 #include "nvim/msgpack_rpc/helpers.h"
 #include "nvim/msgpack_rpc/unpacker.h"
+#include "nvim/ui_client.h"
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "msgpack_rpc/unpacker.c.generated.h"
@@ -280,10 +281,20 @@ error:
 // is relatively small, just ~10 bytes + the method name. Thus we can simply refuse
 // to advance the stream beyond the header until it can be parsed in its entirety.
 //
-// Of course, later on, we want to specialize state 2 into sub-states depending
+// Later on, we want to specialize state 2 into more sub-states depending
 // on the specific method. "nvim_exec_lua" should just decode direct into lua
-// objects, and "redraw/grid_line" should use a hand-rolled decoder to avoid
-// a blizzard of small objects for each screen cell.
+// objects. For the moment "redraw/grid_line" uses a hand-rolled decoder,
+// to avoid a blizzard of small objects for each screen cell.
+//
+// <0>[2, "redraw", <10>[{11}["method", <12>[args], <12>[args], ...], <11>[...], ...]]
+//
+// Where [args] gets unpacked as an Array. Note: first {11} is not saved as a state.
+//
+// When method is "grid_line", we furthermore decode a cell at a time like:
+//
+// <0>[2, "redraw", <10>[{11}["grid_line", <13>[g, r, c, [<14>[cell], <14>[cell], ...]], ...], <11>[...], ...]]
+//
+// where [cell] is [char, repeat, attr], where 'repeat' and 'attr' is optional
 
 bool unpacker_advance(Unpacker *p)
 {
@@ -292,8 +303,27 @@ bool unpacker_advance(Unpacker *p)
     if (!unpacker_parse_header(p)) {
       return false;
     }
-    p->state = p->type == kMessageTypeResponse ? 1 : 2;
-    arena_start(&p->arena, &p->reuse_blk);
+    if (p->type == kMessageTypeNotification && p->handler.fn == handle_ui_client_redraw) {
+      p->type = kMessageTypeRedrawEvent;
+      p->state = 10;
+    } else {
+      p->state = p->type == kMessageTypeResponse ? 1 : 2;
+      arena_start(&p->arena, &p->reuse_blk);
+    }
+  }
+
+  if (p->state >= 10 && p->state != 12) {
+    if (!unpacker_parse_redraw(p)) {
+      return false;
+    }
+
+    if (p->state == 14) {
+      // grid_line event already unpacked
+      goto done;
+    } else {
+      // unpack other ui events using mpack_parse()
+      arena_start(&p->arena, &p->reuse_blk);
+    }
   }
 
   int result;
@@ -310,13 +340,173 @@ rerun:
     return false;
   }
 
-  if (p->state == 1) {
+done:
+  switch (p->state) {
+  case 1:
     p->error = p->result;
     p->state = 2;
     goto rerun;
-  } else {
-    assert(p->state == 2);
+  case 2:
     p->state = 0;
+    return true;
+  case 12:
+  case 14:
+    p->ncalls--;
+    if (p->ncalls > 0) {
+      p->state = (p->state == 14) ? 13 : 12;
+    } else if (p->nevents > 0) {
+      p->state = 11;
+    } else {
+      p->state = 0;
+    }
+    return true;
+  default:
+    abort();
+  }
+}
+
+bool unpacker_parse_redraw(Unpacker *p)
+{
+  mpack_token_t tok;
+  int result;
+
+  const char *data = p->read_ptr;
+  size_t size = p->read_size;
+  GridLineEvent *g = p->grid_line_event;
+
+#define NEXT_TYPE(tok, typ) \
+  result = mpack_rtoken(&data, &size, &tok); \
+  if (result == MPACK_EOF) { \
+    return false; \
+  } else if (result || (tok.type != typ \
+                        && !(typ == MPACK_TOKEN_STR && tok.type == MPACK_TOKEN_BIN) \
+                        && !(typ == MPACK_TOKEN_SINT && tok.type == MPACK_TOKEN_UINT))) { \
+    p->state = -1; \
+    return false; \
+  }
+
+redo:
+  switch (p->state) {
+  case 10:
+    NEXT_TYPE(tok, MPACK_TOKEN_ARRAY);
+    p->nevents = (int)tok.length;
+    FALLTHROUGH;
+
+  case 11:
+    NEXT_TYPE(tok, MPACK_TOKEN_ARRAY);
+    p->ncalls = (int)tok.length;
+
+    if (p->ncalls-- == 0) {
+      p->state = -1;
+      return false;
+    }
+
+    NEXT_TYPE(tok, MPACK_TOKEN_STR);
+    if (tok.length > size) {
+      return false;
+    }
+
+    p->ui_handler = ui_client_get_redraw_handler(data, tok.length, NULL);
+    data += tok.length;
+    size -= tok.length;
+
+    p->nevents--;
+    p->read_ptr = data;
+    p->read_size = size;
+    if (p->ui_handler.fn != ui_client_event_grid_line) {
+      p->state = 12;
+      if (p->grid_line_event) {
+        arena_mem_free(arena_finish(&p->arena), &p->reuse_blk);
+        p->grid_line_event = NULL;
+      }
+      return true;
+    } else {
+      p->state = 13;
+      arena_start(&p->arena, &p->reuse_blk);
+      p->grid_line_event = arena_alloc(&p->arena, sizeof *p->grid_line_event, true);
+      g = p->grid_line_event;
+      FALLTHROUGH;
+    }
+
+  case 13:
+    NEXT_TYPE(tok, MPACK_TOKEN_ARRAY);
+    int eventarrsize = (int)tok.length;
+    if (eventarrsize != 4) {
+      p->state = -1;
+      return false;
+    }
+
+    for (int i = 0; i < 3; i++) {
+      NEXT_TYPE(tok, MPACK_TOKEN_UINT);
+      g->args[i] = (int)tok.data.value.lo;
+    }
+
+    NEXT_TYPE(tok, MPACK_TOKEN_ARRAY);
+    g->ncells = (int)tok.length;
+    g->icell = 0;
+    g->coloff = 0;
+    g->cur_attr = -1;
+
+    p->read_ptr = data;
+    p->read_size = size;
+    p->state = 14;
+    FALLTHROUGH;
+
+  case 14:
+    assert(g->icell < g->ncells);
+
+    NEXT_TYPE(tok, MPACK_TOKEN_ARRAY);
+    int cellarrsize = (int)tok.length;
+    if (cellarrsize < 1 || cellarrsize > 3) {
+      p->state = -1;
+      return false;
+    }
+
+    NEXT_TYPE(tok, MPACK_TOKEN_STR);
+    if (tok.length > size) {
+      return false;
+    }
+
+    const char *cellbuf = data;
+    size_t cellsize = tok.length;
+    data += cellsize;
+    size -= cellsize;
+
+    if (cellarrsize >= 2) {
+      NEXT_TYPE(tok, MPACK_TOKEN_SINT);
+      g->cur_attr = (int)tok.data.value.lo;
+    }
+
+    int repeat = 1;
+    if (cellarrsize >= 3) {
+      NEXT_TYPE(tok, MPACK_TOKEN_UINT);
+      repeat = (int)tok.data.value.lo;
+    }
+
+    g->clear_width = 0;
+    if (g->icell == g->ncells - 1 && cellsize == 1 && cellbuf[0] == ' ' && repeat > 1) {
+      g->clear_width = repeat;
+    } else {
+      for (int r = 0; r < repeat; r++) {
+        if (g->coloff >= (int)grid_line_buf_size) {
+          p->state = -1;
+          return false;
+        }
+        memcpy(grid_line_buf_char[g->coloff], cellbuf, cellsize);
+        grid_line_buf_char[g->coloff][cellsize] = NUL;
+        grid_line_buf_attr[g->coloff++] = g->cur_attr;
+      }
+    }
+
+    g->icell++;
+    p->read_ptr = data;
+    p->read_size = size;
+    if (g->icell == g->ncells) {
+      return true;
+    }
+    goto redo;
+
+  default:
+    abort();
   }
-  return true;
 }
diff --git a/src/nvim/msgpack_rpc/unpacker.h b/src/nvim/msgpack_rpc/unpacker.h
index e0dc6f0a68..f39439be63 100644
--- a/src/nvim/msgpack_rpc/unpacker.h
+++ b/src/nvim/msgpack_rpc/unpacker.h
@@ -32,8 +32,13 @@ struct Unpacker {
   Error unpack_error;
 
   Arena arena;
-  // one lenght free-list of reusable blocks
+  // one length free-list of reusable blocks
   ArenaMem reuse_blk;
+
+  int nevents;
+  int ncalls;
+  UIClientHandler ui_handler;
+  GridLineEvent *grid_line_event;
 };
 
 // unrecovareble error. unpack_error should be set!
diff --git a/src/nvim/ui.c b/src/nvim/ui.c
index a49e9df9ee..e958f02e32 100644
--- a/src/nvim/ui.c
+++ b/src/nvim/ui.c
@@ -348,7 +348,8 @@ void ui_attach_impl(UI *ui, uint64_t chanid)
   if (ui_count == MAX_UI_COUNT) {
     abort();
   }
-  if (!ui->ui_ext[kUIMultigrid] && !ui->ui_ext[kUIFloatDebug]) {
+  if (!ui->ui_ext[kUIMultigrid] && !ui->ui_ext[kUIFloatDebug]
+      && !ui_client_channel_id) {
     ui_comp_attach(ui);
   }
 
@@ -502,6 +503,9 @@ handle_T ui_cursor_grid(void)
 
 void ui_flush(void)
 {
+  if (!ui_active()) {
+    return;
+  }
   cmdline_ui_flush();
   win_ui_flush();
   msg_ext_ui_flush();
diff --git a/src/nvim/ui_client.c b/src/nvim/ui_client.c
index be01538f67..09e971f03f 100644
--- a/src/nvim/ui_client.c
+++ b/src/nvim/ui_client.c
@@ -22,11 +22,6 @@
 # include "ui_events_client.generated.h"
 #endif
 
-// Temporary buffer for converting a single grid_line event
-static size_t buf_size = 0;
-static schar_T *buf_char = NULL;
-static sattr_T *buf_attr = NULL;
-
 void ui_client_init(uint64_t chan)
 {
   Array args = ARRAY_DICT_INIT;
@@ -46,37 +41,23 @@ void ui_client_init(uint64_t chan)
   ui_client_channel_id = chan;
 }
 
-/// Handler for "redraw" events sent by the NVIM server
-///
-/// This function will be called by handle_request (in msgpack_rpc/channel.c)
-/// The individual ui_events sent by the server are individually handled
-/// by their respective handlers defined in ui_events_client.generated.h
-///
-/// @note The "flush" event is called only once and only after handling all
-///       the other events
-/// @param channel_id: The id of the rpc channel
-/// @param uidata: The dense array containing the ui_events sent by the server
-/// @param[out] err Error details, if any
-Object handle_ui_client_redraw(uint64_t channel_id, Array args, Error *error)
+UIClientHandler ui_client_get_redraw_handler(const char *name, size_t name_len, Error *error)
 {
-  for (size_t i = 0; i < args.size; i++) {
-    Array call = args.items[i].data.array;
-    String name = call.items[0].data.string;
-
-    int hash = ui_client_handler_hash(name.data, name.size);
-    if (hash < 0) {
-      ELOG("No ui client handler for %s", name.size ? name.data : "<empty>");
-      continue;
-    }
-    UIClientHandler handler = event_handlers[hash];
-
-    // fprintf(stderr, "%s: %zu\n", name.data, call.size-1);
-    DLOG("Invoke ui client handler for %s", name.data);
-    for (size_t j = 1; j < call.size; j++) {
-      handler.fn(call.items[j].data.array);
-    }
+  int hash = ui_client_handler_hash(name, name_len);
+  if (hash < 0) {
+    return (UIClientHandler){ NULL, NULL };
   }
+  return event_handlers[hash];
+}
 
+/// Placeholder for _sync_ requests with 'redraw' method name
+///
+/// async 'redraw' events, which are expected when nvim acts as an ui client.
+/// get handled in msgpack_rpc/unpacker.c and directy dispatched to handlers
+/// of specific ui events, like ui_client_event_grid_resize and so on.
+Object handle_ui_client_redraw(uint64_t channel_id, Array args, Error *error)
+{
+  api_set_error(error, kErrorTypeValidation, "'redraw' cannot be sent as a request");
   return NIL;
 }
 
@@ -120,88 +101,30 @@ void ui_client_event_grid_resize(Array args)
   Integer height = args.items[2].data.integer;
   ui_call_grid_resize(grid, width, height);
 
-  if (buf_size < (size_t)width) {
-    xfree(buf_char);
-    xfree(buf_attr);
-    buf_size = (size_t)width;
-    buf_char = xmalloc(buf_size * sizeof(schar_T));
-    buf_attr = xmalloc(buf_size * sizeof(sattr_T));
+  if (grid_line_buf_size < (size_t)width) {
+    xfree(grid_line_buf_char);
+    xfree(grid_line_buf_attr);
+    grid_line_buf_size = (size_t)width;
+    grid_line_buf_char = xmalloc(grid_line_buf_size * sizeof(schar_T));
+    grid_line_buf_attr = xmalloc(grid_line_buf_size * sizeof(sattr_T));
   }
 }
 
 void ui_client_event_grid_line(Array args)
+  FUNC_ATTR_NORETURN
 {
-  if (args.size < 4
-      || args.items[0].type != kObjectTypeInteger
-      || args.items[1].type != kObjectTypeInteger
-      || args.items[2].type != kObjectTypeInteger
-      || args.items[3].type != kObjectTypeArray) {
-    goto error;
-  }
+  abort();  // unreachable
+}
 
-  Integer grid = args.items[0].data.integer;
-  Integer row = args.items[1].data.integer;
-  Integer startcol = args.items[2].data.integer;
-  Array cells = args.items[3].data.array;
+void ui_client_event_raw_line(GridLineEvent *g)
+{
+  int grid = g->args[0], row = g->args[1], startcol = g->args[2];
+  Integer endcol = startcol + g->coloff;
+  Integer clearcol = endcol + g->clear_width;
 
   // TODO(hlpr98): Accommodate other LineFlags when included in grid_line
   LineFlags lineflags = 0;
 
-  size_t j = 0;
-  int cur_attr = 0;
-  int clear_attr = 0;
-  int clear_width = 0;
-  for (size_t i = 0; i < cells.size; i++) {
-    if (cells.items[i].type != kObjectTypeArray) {
-      goto error;
-    }
-    Array cell = cells.items[i].data.array;
-
-    if (cell.size < 1 || cell.items[0].type != kObjectTypeString) {
-      goto error;
-    }
-    String sstring = cell.items[0].data.string;
-
-    char *schar = sstring.data;
-    int repeat = 1;
-    if (cell.size >= 2) {
-      if (cell.items[1].type != kObjectTypeInteger
-          || cell.items[1].data.integer < 0) {
-        goto error;
-      }
-      cur_attr = (int)cell.items[1].data.integer;
-    }
-
-    if (cell.size >= 3) {
-      if (cell.items[2].type != kObjectTypeInteger
-          || cell.items[2].data.integer < 0) {
-        goto error;
-      }
-      repeat = (int)cell.items[2].data.integer;
-    }
-
-    if (i == cells.size - 1 && sstring.size == 1 && sstring.data[0] == ' ' && repeat > 1) {
-      clear_width = repeat;
-      break;
-    }
-
-    for (int r = 0; r < repeat; r++) {
-      if (j >= buf_size) {
-        goto error;  // _YIKES_
-      }
-      STRLCPY(buf_char[j], schar, sizeof(schar_T));
-      buf_attr[j++] = cur_attr;
-    }
-  }
-
-  Integer endcol = startcol + (int)j;
-  Integer clearcol = endcol + clear_width;
-  clear_attr = cur_attr;
-
-  ui_call_raw_line(grid, row, startcol, endcol, clearcol, clear_attr, lineflags,
-                   (const schar_T *)buf_char, (const sattr_T *)buf_attr);
-  return;
-
-error:
-  ELOG("Error handling ui event 'grid_line'");
+  ui_call_raw_line(grid, row, startcol, endcol, clearcol, g->cur_attr, lineflags,
+                   (const schar_T *)grid_line_buf_char, grid_line_buf_attr);
 }
diff --git a/src/nvim/ui_client.h b/src/nvim/ui_client.h
index 41d9fa6227..311dafaa0b 100644
--- a/src/nvim/ui_client.h
+++ b/src/nvim/ui_client.h
@@ -2,12 +2,18 @@
 #define NVIM_UI_CLIENT_H
 
 #include "nvim/api/private/defs.h"
+#include "nvim/grid_defs.h"
 
 typedef struct {
   const char *name;
   void (*fn)(Array args);
 } UIClientHandler;
 
+// Temporary buffer for converting a single grid_line event
+EXTERN size_t grid_line_buf_size INIT(= 0);
+EXTERN schar_T *grid_line_buf_char INIT(= NULL);
+EXTERN sattr_T *grid_line_buf_attr INIT(= NULL);
+
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "ui_client.h.generated.h"
 
diff --git a/test/functional/editor/put_spec.lua b/test/functional/editor/put_spec.lua
index cc9fce8f67..5050edff5c 100644
--- a/test/functional/editor/put_spec.lua
+++ b/test/functional/editor/put_spec.lua
@@ -879,9 +879,13 @@ describe('put command', function()
 	ine of words 2]], curbuf_contents())
     end)
 
-    local function bell_test(actions, should_ring)
-      local screen = Screen.new()
+    local screen
+    setup(function()
+      screen = Screen.new()
       screen:attach()
+    end)
+
+    local function bell_test(actions, should_ring)
       if should_ring then
         -- check bell is not set by nvim before the action
         screen:sleep(50)
@@ -899,7 +903,6 @@ describe('put command', function()
           end
         end
       end, unchanged=(not should_ring)}
-      screen:detach()
     end
 
     it('should not ring the bell with gp at end of line', function()
diff --git a/test/functional/ui/cursor_spec.lua b/test/functional/ui/cursor_spec.lua
index a1423c98a8..03cd4bfd06 100644
--- a/test/functional/ui/cursor_spec.lua
+++ b/test/functional/ui/cursor_spec.lua
@@ -215,7 +215,7 @@ describe('ui/cursor', function()
           m.hl_id = 60
           m.attr = {background = Screen.colors.DarkGray}
       end
-      if m.id_lm then m.id_lm = 65 end
+      if m.id_lm then m.id_lm = 61 end
     end
 
     -- Assert the new expectation.
diff --git a/test/functional/ui/options_spec.lua b/test/functional/ui/options_spec.lua
index c2b0bcdb64..8d7c404637 100644
--- a/test/functional/ui/options_spec.lua
+++ b/test/functional/ui/options_spec.lua
@@ -51,7 +51,7 @@ describe('UI receives option updates', function()
   end)
 
   it('on attach #11372', function()
-    clear()
+    clear{args_rm={'--headless'}}
     local evs = {}
     screen = Screen.new(20,5)
     -- Override mouse_on/mouse_off handlers.
@@ -88,6 +88,13 @@ describe('UI receives option updates', function()
       eq(expected, screen.options)
     end)
 
+    command("set pumblend=50")
+    expected.pumblend = 50
+    screen:expect(function()
+        eq(expected, screen.options)
+    end)
+
+    -- check handling of out-of-bounds value
     command("set pumblend=-1")
     expected.pumblend = 0
     screen:expect(function()