perf(redraw): only redraw Visual area when cursor has moved (#27340)

src/nvim/move.c

@@ -147,6 +147,9 @@ static void redraw_for_cursorcolumn(win_T *wp)
       // When 'cursorcolumn' is set or "CurSearch" is in use
       // need to redraw with UPD_SOME_VALID.
       redraw_later(wp, UPD_SOME_VALID);
+    } else if (VIsual_active) {
+      // In Visual mode need to redraw with UPD_INVERTED.
+      redraw_later(wp, UPD_INVERTED);
     } else if (wp->w_p_cul && (wp->w_p_culopt_flags & CULOPT_SCRLINE)) {
       // When 'cursorlineopt' contains "screenline" need to redraw with UPD_VALID.
       redraw_later(wp, UPD_VALID);

src/nvim/normal.c

@@ -1347,10 +1347,6 @@ static void normal_redraw(NormalState *s)
 
   show_cursor_info_later(false);
 
-  if (VIsual_active) {
-    redraw_curbuf_later(UPD_INVERTED);  // update inverted part
-  }
-
   if (must_redraw) {
     update_screen();
   } else {
@@ -5129,6 +5125,7 @@ static void n_start_visual_mode(int c)
     curwin->w_old_cursor_lnum = curwin->w_cursor.lnum;
     curwin->w_old_visual_lnum = curwin->w_cursor.lnum;
   }
+  redraw_curbuf_later(UPD_VALID);
 }
 
 /// CTRL-W: Window commands

src/nvim/optionstr.c

@@ -1541,7 +1541,15 @@ int expand_set_formatoptions(optexpand_T *args, int *numMatches, char ***matches
 /// The 'guicursor' option is changed.
 const char *did_set_guicursor(optset_T *args FUNC_ATTR_UNUSED)
 {
-  return parse_shape_opt(SHAPE_CURSOR);
+  const char *errmsg = parse_shape_opt(SHAPE_CURSOR);
+  if (errmsg != NULL) {
+    return errmsg;
+  }
+  if (VIsual_active) {
+    // In Visual mode cursor may be drawn differently.
+    redrawWinline(curwin, curwin->w_cursor.lnum);
+  }
+  return NULL;
 }
 
 /// The 'helpfile' option is changed.
@@ -1958,6 +1966,10 @@ const char *did_set_selection(optset_T *args FUNC_ATTR_UNUSED)
   if (*p_sel == NUL || check_opt_strings(p_sel, p_sel_values, false) != OK) {
     return e_invarg;
   }
+  if (VIsual_active) {
+    // In Visual mode cursor may be drawn differently.
+    redrawWinline(curwin, curwin->w_cursor.lnum);
+  }
   return NULL;
 }
 

test/functional/ui/decorations_spec.lua

@@ -39,6 +39,7 @@ describe('decorations providers', function()
       [16] = {special = Screen.colors.Red, undercurl = true},
       [17] = {foreground = Screen.colors.Red},
       [18] = {bold = true, foreground = Screen.colors.SeaGreen};
+      [19] = {bold = true};
     }
   end)
 
@@ -738,6 +739,25 @@ describe('decorations providers', function()
                                               |
     ]]}
   end)
+
+  it('is not invoked repeatedly in Visual mode with vim.schedule() #20235', function()
+    exec_lua([[_G.cnt = 0]])
+    setup_provider([[
+      function on_do(event, ...)
+        if event == 'win' then
+          vim.schedule(function() end)
+          _G.cnt = _G.cnt + 1
+        end
+      end
+    ]])
+    feed('v')
+    screen:expect([[
+      ^                                        |
+      {1:~                                       }|*6
+      {19:-- VISUAL --}                            |
+    ]])
+    eq(2, exec_lua([[return _G.cnt]]))
+  end)
 end)
 
 local example_text = [[