fix(ui): superfluous showmode / excessive grid_cursor_goto #29089

Problem:  Unsetting global variables earlier in #28578 to avoid
          recursiveness, caused superfluous or even unlimited
          showmode().
Solution: Partly revert #28578 so that the globals are unset at the end
          of showmode(), and avoid recursiveness for ext UI by adding a
          recursive function guard to each generated UI call that may
          call a Lua callback.

1 files changed, 10 insertions, 12 deletions

diff --git a/src/nvim/drawscreen.c b/src/nvim/drawscreen.c
index bd9a834869..88e1f302da 100644
--- a/src/nvim/drawscreen.c
+++ b/src/nvim/drawscreen.c
@@ -931,13 +931,7 @@ int showmode(void)
     msg_ext_clear(true);
   }
 
-  // Don't make non-flushed message part of the showmode and reset global
-  // variables before flushing to to avoid recursiveness.
-  bool draw_mode = redraw_mode;
-  bool clear_cmd = clear_cmdline;
-  redraw_cmdline = false;
-  redraw_mode = false;
-  clear_cmdline = false;
+  // Don't make non-flushed message part of the showmode.
   msg_ext_ui_flush();
 
   msg_grid_validate();
@@ -960,8 +954,8 @@ int showmode(void)
     msg_check_for_delay(false);
 
     // if the cmdline is more than one line high, erase top lines
-    bool need_clear = clear_cmd;
-    if (clear_cmd && cmdline_row < Rows - 1) {
+    bool need_clear = clear_cmdline;
+    if (clear_cmdline && cmdline_row < Rows - 1) {
       msg_clr_cmdline();  // will reset clear_cmdline
     }
 
@@ -1083,7 +1077,7 @@ int showmode(void)
     }
 
     mode_displayed = true;
-    if (need_clear || clear_cmd || draw_mode) {
+    if (need_clear || clear_cmdline || redraw_mode) {
       msg_clr_eos();
     }
     msg_didout = false;                 // overwrite this message
@@ -1092,10 +1086,10 @@ int showmode(void)
     msg_no_more = false;
     lines_left = save_lines_left;
     need_wait_return = nwr_save;        // never ask for hit-return for this
-  } else if (clear_cmd && msg_silent == 0) {
+  } else if (clear_cmdline && msg_silent == 0) {
     // Clear the whole command line.  Will reset "clear_cmdline".
     msg_clr_cmdline();
-  } else if (draw_mode) {
+  } else if (redraw_mode) {
     msg_pos_mode();
     msg_clr_eos();
   }
@@ -1118,6 +1112,10 @@ int showmode(void)
     grid_line_flush();
   }
 
+  redraw_cmdline = false;
+  redraw_mode = false;
+  clear_cmdline = false;
+
   return length;
 }