UI/cmdline: check if redraw is needed after K_EVENT, K_COMMAND #9804

fixes #8490

src/nvim/ex_getln.c

@@ -547,7 +547,10 @@ static int command_line_execute(VimState *state, int key)
     } else {
       do_cmdline(NULL, getcmdkeycmd, NULL, DOCMD_NOWAIT);
     }
-    redrawcmdline();
+
+    if (!cmdline_was_last_drawn) {
+      redrawcmdline();
+    }
     return 1;
   }
 
@@ -3457,6 +3460,8 @@ void redrawcmd(void)
     return;
   }
 
+  redrawing_cmdline = true;
+
   msg_start();
   redrawcmdprompt();
 
@@ -3478,9 +3483,11 @@ void redrawcmd(void)
    */
   msg_scroll = FALSE;           /* next message overwrites cmdline */
 
-  /* Typing ':' at the more prompt may set skip_redraw.  We don't want this
-   * in cmdline mode */
-  skip_redraw = FALSE;
+  // Typing ':' at the more prompt may set skip_redraw.  We don't want this
+  // in cmdline mode.
+  skip_redraw = false;
+
+  redrawing_cmdline = false;
 }
 
 void compute_cmdrow(void)

src/nvim/globals.h

@@ -146,12 +146,14 @@ EXTERN int mod_mask INIT(= 0x0);                /* current key modifiers */
  */
 EXTERN int cmdline_row;
 
-EXTERN int redraw_cmdline INIT(= FALSE);        /* cmdline must be redrawn */
-EXTERN int clear_cmdline INIT(= FALSE);         /* cmdline must be cleared */
-EXTERN int mode_displayed INIT(= FALSE);        /* mode is being displayed */
-EXTERN int cmdline_star INIT(= FALSE);          /* cmdline is crypted */
+EXTERN int redraw_cmdline INIT(= false);          // cmdline must be redrawn
+EXTERN int clear_cmdline INIT(= false);           // cmdline must be cleared
+EXTERN int mode_displayed INIT(= false);          // mode is being displayed
+EXTERN int cmdline_star INIT(= false);            // cmdline is crypted
+EXTERN int redrawing_cmdline INIT(= false);       // cmdline is being redrawn
+EXTERN int cmdline_was_last_drawn INIT(= false);  // cmdline was last drawn
 
-EXTERN int exec_from_reg INIT(= FALSE);         /* executing register */
+EXTERN int exec_from_reg INIT(= false);         // executing register
 
 /*
  * When '$' is included in 'cpoptions' option set:

src/nvim/message.c

@@ -1881,6 +1881,8 @@ static void msg_puts_display(const char_u *str, int maxlen, int attr,
     return;
   }
 
+  cmdline_was_last_drawn = redrawing_cmdline;
+
   while ((maxlen < 0 || (int)(s - str) < maxlen) && *s != NUL) {
     // We are at the end of the screen line when:
     // - When outputting a newline.

src/nvim/screen.c

@@ -507,6 +507,8 @@ void update_screen(int type)
     maybe_intro_message();
   did_intro = TRUE;
 
+  // either cmdline is cleared, not drawn or mode is last drawn
+  cmdline_was_last_drawn = false;
 }
 
 /*

test/functional/ui/cmdline_spec.lua

@@ -4,20 +4,25 @@ local clear, feed = helpers.clear, helpers.feed
 local source = helpers.source
 local command = helpers.command
 
+local function new_screen(opt)
+  local screen = Screen.new(25, 5)
+  screen:attach(opt)
+  screen:set_default_attr_ids({
+    [1] = {bold = true, foreground = Screen.colors.Blue1},
+    [2] = {reverse = true},
+    [3] = {bold = true, reverse = true},
+    [4] = {foreground = Screen.colors.Grey100, background = Screen.colors.Red},
+    [5] = {bold = true, foreground = Screen.colors.SeaGreen4},
+  })
+  return screen
+end
+
 local function test_cmdline(linegrid)
   local screen
 
   before_each(function()
     clear()
-    screen = Screen.new(25, 5)
-    screen:attach({rgb=true, ext_cmdline=true, ext_linegrid=linegrid})
-    screen:set_default_attr_ids({
-      [1] = {bold = true, foreground = Screen.colors.Blue1},
-      [2] = {reverse = true},
-      [3] = {bold = true, reverse = true},
-      [4] = {foreground = Screen.colors.Grey100, background = Screen.colors.Red},
-      [5] = {bold = true, foreground = Screen.colors.SeaGreen4},
-    })
+    screen = new_screen({rgb=true, ext_cmdline=true, ext_linegrid=linegrid})
   end)
 
   after_each(function()
@@ -758,6 +763,57 @@ local function test_cmdline(linegrid)
 
 end
 
+describe('cmdline redraw', function()
+  local screen
+  before_each(function()
+    clear()
+    screen = new_screen({rgb=true})
+  end)
+
+  after_each(function()
+    screen:detach()
+  end)
+
+  it('with timer', function()
+    feed(':012345678901234567890123456789')
+    screen:expect{grid=[[
+                             |
+    {1:~                        }|
+    {3:                         }|
+    :012345678901234567890123|
+    456789^                   |
+    ]]}
+    command('call timer_start(0, {-> 1})')
+    screen:expect{grid=[[
+                             |
+    {1:~                        }|
+    {3:                         }|
+    :012345678901234567890123|
+    456789^                   |
+    ]], unchanged=true, timeout=100}
+  end)
+
+  it('with <Cmd>', function()
+    command('cmap a <Cmd>0<CR>')  -- no-op
+    feed(':012345678901234567890123456789')
+    screen:expect{grid=[[
+                             |
+    {1:~                        }|
+    {3:                         }|
+    :012345678901234567890123|
+    456789^                   |
+    ]]}
+    feed('a')
+    screen:expect{grid=[[
+                             |
+    {1:~                        }|
+    {3:                         }|
+    :012345678901234567890123|
+    456789^                   |
+    ]], unchanged=true}
+  end)
+end)
+
 -- the representation of cmdline and cmdline_block contents changed with ext_linegrid
 -- (which uses indexed highlights) so make sure to test both
 describe('ui/ext_cmdline', function() test_cmdline(true) end)