fix(ui): propagate line wrapping state on grid_line events

This fixes the TUI's line-wrapping behavior, which was broken with the
migration to the msgpack-based UI protocol (see
https://github.com/neovim/neovim/issues/7369#issuecomment-1571812273).

runtime/doc/ui.txt

@@ -78,14 +78,14 @@ Example of a typical "redraw" batch in a single RPC notification: >
       [
 	['grid_resize', [2, 77, 36]],
 	['grid_line',
-	  [2, 0, 0, [[' ' , 0, 77]]],
+	  [2, 0, 0, [[' ' , 0, 77]], false],
-	  [2, 1, 0, [['~', 7], [' ', 7, 76]]],
+	  [2, 1, 0, [['~', 7], [' ', 7, 76]], false],
-	  [2, 9, 0, [['~', 7], [' ', 7, 76]]], 
+	  [2, 9, 0, [['~', 7], [' ', 7, 76]], false],
 	  ...
-	  [2, 35, 0, [['~', 7], [' ', 7, 76]]],
+	  [2, 35, 0, [['~', 7], [' ', 7, 76]], false],
-	  [1, 36, 0, [['[', 9], ['N'], ['o'], [' '], ['N'], ['a'], ['m'], ['e'], [']']]],
+	  [1, 36, 0, [['[', 9], ['N'], ['o'], [' '], ['N'], ['a'], ['m'], ['e'], [']']], false],
-	  [1, 36, 9, [[' ', 9, 50]]],
+	  [1, 36, 9, [[' ', 9, 50]], false],
-	  [1, 36, 59, [['0', 9], [','], ['0'], ['-' ], ['1'], [' ', 9, 10], ['A'], ['l', 9, 2]]]
+	  [1, 36, 59, [['0', 9], [','], ['0'], ['-' ], ['1'], [' ', 9, 10], ['A'], ['l', 9, 2]], false]
 	],
 	['msg_showmode', [[]]],
 	['win_pos', [2, 1000, 0, 0, 77, 36]],
@@ -360,7 +360,7 @@ numerical highlight ids to the actual attributes.
 	use the |hl-Pmenu| family of builtin highlights.
 
 							    *ui-event-grid_line*
-["grid_line", grid, row, col_start, cells] ~
+["grid_line", grid, row, col_start, cells, wrap] ~
 	Redraw a continuous part of a `row` on a `grid`, starting at the column
 	`col_start`. `cells` is an array of arrays each with 1 to 3 items:
 	`[text(, hl_id, repeat)]` . `text` is the UTF-8 text that should be put in
@@ -379,6 +379,12 @@ numerical highlight ids to the actual attributes.
 	enough to cover the remaining line, will be sent when the rest of the
 	line should be cleared.
 
+	`wrap` is a boolean indicating that this line wraps to the next row.
+	When redrawing a line which wraps to the next row, Nvim will emit a
+	`grid_line` event covering the last column of the line with `wrap` set
+	to true, followed immediately by a `grid_line` event starting at the
+	first column of the next row.
+
 ["grid_clear", grid] ~
 	Clear a `grid`.
 

src/nvim/api/ui.c

@@ -73,6 +73,11 @@ static void mpack_uint(char **buf, uint32_t val)
   }
 }
 
+static void mpack_bool(char **buf, bool val)
+{
+  mpack_w(buf, 0xc2 | val);
+}
+
 static void mpack_array(char **buf, uint32_t len)
 {
   if (len < 0x10) {
@@ -809,7 +814,7 @@ void remote_ui_raw_line(UI *ui, Integer grid, Integer row, Integer startcol, Int
     data->ncalls++;
 
     char **buf = &data->buf_wptr;
-    mpack_array(buf, 4);
+    mpack_array(buf, 5);
     mpack_uint(buf, (uint32_t)grid);
     mpack_uint(buf, (uint32_t)row);
     mpack_uint(buf, (uint32_t)startcol);
@@ -823,17 +828,20 @@ void remote_ui_raw_line(UI *ui, Integer grid, Integer row, Integer startcol, Int
       repeat++;
       if (i == ncells - 1 || attrs[i] != attrs[i + 1]
           || strcmp(chunk[i], chunk[i + 1]) != 0) {
-        if (UI_BUF_SIZE - BUF_POS(data) < 2 * (1 + 2 + sizeof(schar_T) + 5 + 5)) {
+        if (UI_BUF_SIZE - BUF_POS(data) < 2 * (1 + 2 + sizeof(schar_T) + 5 + 5) + 1) {
           // 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.
           mpack_w2(&lenpos, nelem);
+
+          // We only ever set the wrap field on the final "grid_line" event for the line.
+          mpack_bool(buf, false);
           remote_ui_flush_buf(ui);
 
           prepare_call(ui, "grid_line");
           data->ncalls++;
-          mpack_array(buf, 4);
+          mpack_array(buf, 5);
           mpack_uint(buf, (uint32_t)grid);
           mpack_uint(buf, (uint32_t)row);
           mpack_uint(buf, (uint32_t)startcol + (uint32_t)i - repeat + 1);
@@ -865,9 +873,10 @@ void remote_ui_raw_line(UI *ui, Integer grid, Integer row, Integer startcol, Int
       mpack_uint(buf, (uint32_t)(clearcol - endcol));
     }
     mpack_w2(&lenpos, nelem);
+    mpack_bool(buf, flags & kLineFlagWrap);
 
     if (data->ncells_pending > 500) {
-      // pass of cells to UI to let it start processing them
+      // pass off cells to UI to let it start processing them
       remote_ui_flush_buf(ui);
     }
   } else {

src/nvim/api/ui_events.in.h

@@ -82,7 +82,7 @@ void grid_clear(Integer grid)
   FUNC_API_SINCE(5) FUNC_API_REMOTE_IMPL;
 void grid_cursor_goto(Integer grid, Integer row, Integer col)
   FUNC_API_SINCE(5) FUNC_API_REMOTE_IMPL FUNC_API_COMPOSITOR_IMPL;
-void grid_line(Integer grid, Integer row, Integer col_start, Array data)
+void grid_line(Integer grid, Integer row, Integer col_start, Array data, Boolean wrap)
   FUNC_API_SINCE(5) FUNC_API_REMOTE_ONLY FUNC_API_CLIENT_IMPL;
 void grid_scroll(Integer grid, Integer top, Integer bot, Integer left, Integer right, Integer rows,
                  Integer cols)

src/nvim/grid_defs.h

@@ -117,6 +117,7 @@ typedef struct {
   int coloff;
   int cur_attr;
   int clear_width;
+  bool wrap;
 } GridLineEvent;
 
 #endif  // NVIM_GRID_DEFS_H

src/nvim/msgpack_rpc/unpacker.c

@@ -441,7 +441,7 @@ redo:
   case 14:
     NEXT_TYPE(tok, MPACK_TOKEN_ARRAY);
     int eventarrsize = (int)tok.length;
-    if (eventarrsize != 4) {
+    if (eventarrsize != 5) {
       p->state = -1;
       return false;
     }
@@ -509,11 +509,16 @@ redo:
     }
 
     g->icell++;
-    p->read_ptr = data;
-    p->read_size = size;
     if (g->icell == g->ncells) {
+      NEXT_TYPE(tok, MPACK_TOKEN_BOOLEAN);
+      g->wrap = mpack_unpack_boolean(tok);
+      p->read_ptr = data;
+      p->read_size = size;
       return true;
     }
+
+    p->read_ptr = data;
+    p->read_size = size;
     goto redo;
 
   case 12:

src/nvim/ui_client.c

@@ -210,9 +210,7 @@ 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;
-
+  LineFlags lineflags = g->wrap ? kLineFlagWrap : 0;
-  // TODO(hlpr98): Accommodate other LineFlags when included in grid_line
-  LineFlags lineflags = 0;
 
   tui_raw_line(tui, grid, row, startcol, endcol, clearcol, g->cur_attr, lineflags,
                (const schar_T *)grid_line_buf_char, grid_line_buf_attr);