Merge pull request #20249 from bfredl/cmdmessage

fix(redraw): avoid unnecessary redraws and glitches with floats+messages

18 files changed, 587 insertions, 124 deletions

diff --git a/runtime/lua/man.lua b/runtime/lua/man.lua
index f0306f4871..88535321ac 100644
--- a/runtime/lua/man.lua
+++ b/runtime/lua/man.lua
@@ -21,13 +21,15 @@ local function man_system(cmd, silent)
   local done = false
   local exit_code
 
-  local handle = vim.loop.spawn(cmd[1], {
+  local handle
+  handle = vim.loop.spawn(cmd[1], {
     args = vim.list_slice(cmd, 2),
     stdio = { nil, stdout, stderr },
   }, function(code)
     exit_code = code
     stdout:close()
     stderr:close()
+    handle:close()
     done = true
   end)
 
@@ -52,7 +54,7 @@ local function man_system(cmd, silent)
 
   if not done then
     if handle then
-      vim.loop.shutdown(handle)
+      handle:close()
       stdout:close()
       stderr:close()
     end
diff --git a/src/nvim/autocmd.c b/src/nvim/autocmd.c
index dafbae5813..644f892f3c 100644
--- a/src/nvim/autocmd.c
+++ b/src/nvim/autocmd.c
@@ -1445,7 +1445,6 @@ win_found:
     }
 
     aucmd_win_used = false;
-    last_status(false);  // may need to remove last status line
 
     if (!valid_tabpage_win(curtab)) {
       // no valid window in current tabpage
diff --git a/src/nvim/decoration.c b/src/nvim/decoration.c
index 778f9293fb..5a1708a57c 100644
--- a/src/nvim/decoration.c
+++ b/src/nvim/decoration.c
@@ -75,12 +75,11 @@ void decor_redraw(buf_T *buf, int row1, int row2, Decoration *decor)
   }
 
   if (decor && decor_virt_pos(*decor)) {
-    redraw_buf_line_later(buf, row1 + 1);
+    redraw_buf_line_later(buf, row1 + 1, false);
   }
 
   if (decor && kv_size(decor->virt_lines)) {
-    redraw_buf_line_later(buf, MIN(buf->b_ml.ml_line_count,
-                                   row1 + 1 + (decor->virt_lines_above?0:1)));
+    redraw_buf_line_later(buf, row1 + 1 + (decor->virt_lines_above?0:1), true);
   }
 }
 
diff --git a/src/nvim/drawline.c b/src/nvim/drawline.c
index 25ea2e1000..5c3fa3d3b0 100644
--- a/src/nvim/drawline.c
+++ b/src/nvim/drawline.c
@@ -2638,6 +2638,7 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, bool nochange,
       // When the window is too narrow draw all "@" lines.
       if (draw_state != WL_LINE && filler_todo <= 0) {
         win_draw_end(wp, '@', ' ', true, row, wp->w_grid.rows, HLF_AT);
+        set_empty_rows(wp, row);
         row = endrow;
       }
 
diff --git a/src/nvim/drawscreen.c b/src/nvim/drawscreen.c
index 957e8ae4da..c95f3f3550 100644
--- a/src/nvim/drawscreen.c
+++ b/src/nvim/drawscreen.c
@@ -389,6 +389,10 @@ int update_screen(int type)
     diff_redraw(true);
   }
 
+  // TODO(bfredl): completely get rid of using update_screen(UPD_XX_VALID)
+  // to redraw curwin
+  int curwin_type = MIN(type, UPD_NOT_VALID);
+
   if (must_redraw) {
     if (type < must_redraw) {       // use maximal type
       type = must_redraw;
@@ -445,9 +449,11 @@ int update_screen(int type)
     }
     if (msg_use_msgsep()) {
       msg_grid.throttled = false;
+      bool was_invalidated = false;
+
       // UPD_CLEAR is already handled
       if (type == UPD_NOT_VALID && !ui_has(kUIMultigrid) && msg_scrolled) {
-        ui_comp_set_screen_valid(false);
+        was_invalidated = ui_comp_set_screen_valid(false);
         for (int i = valid; i < Rows - p_ch; i++) {
           grid_clear_line(&default_grid, default_grid.line_offset[i],
                           Columns, false);
@@ -457,6 +463,8 @@ int update_screen(int type)
             continue;
           }
           if (W_ENDROW(wp) > valid) {
+            // TODO(bfredl): too pessimistic. type could be UPD_NOT_VALID
+            // only because windows that are above the separator.
             wp->w_redr_type = MAX(wp->w_redr_type, UPD_NOT_VALID);
           }
           if (!is_stl_global && W_ENDROW(wp) + wp->w_status_height > valid) {
@@ -469,9 +477,16 @@ int update_screen(int type)
       }
       msg_grid_set_pos(Rows - (int)p_ch, false);
       msg_grid_invalid = false;
+      if (was_invalidated) {
+        // screen was only invalid for the msgarea part.
+        // @TODO(bfredl): using the same "valid" flag
+        // for both messages and floats moving is bit of a mess.
+        ui_comp_set_screen_valid(true);
+      }
     } else if (type != UPD_CLEAR) {
       if (msg_scrolled > Rows - 5) {  // redrawing is faster
         type = UPD_NOT_VALID;
+        curwin_type = UPD_NOT_VALID;
       } else {
         check_for_delay(false);
         grid_ins_lines(&default_grid, 0, msg_scrolled, Rows, 0, Columns);
@@ -506,7 +521,7 @@ int update_screen(int type)
     need_wait_return = false;
   }
 
-  win_ui_flush();
+  win_ui_flush(true);
   msg_ext_check_clear();
 
   // reset cmdline_row now (may have been changed temporarily)
@@ -553,6 +568,8 @@ int update_screen(int type)
 
   // Force redraw when width of 'number' or 'relativenumber' column
   // changes.
+  // TODO(bfredl): special casing curwin here is SÅ JÄVLA BULL.
+  // Either this should be done for all windows or not at all.
   if (curwin->w_redr_type < UPD_NOT_VALID
       && curwin->w_nrwidth != ((curwin->w_p_nu || curwin->w_p_rnu)
                                ? number_width(curwin) : 0)) {
@@ -560,22 +577,25 @@ int update_screen(int type)
   }
 
   // Only start redrawing if there is really something to do.
-  if (type == UPD_INVERTED) {
+  // TODO(bfredl): more curwin special casing to get rid of.
+  // Change update_screen(UPD_INVERTED) to a wrapper function
+  // perhaps?
+  if (curwin_type == UPD_INVERTED) {
     update_curswant();
   }
-  if (curwin->w_redr_type < type
-      && !((type == UPD_VALID
+  if (curwin->w_redr_type < curwin_type
+      && !((curwin_type == UPD_VALID
             && curwin->w_lines[0].wl_valid
             && curwin->w_topfill == curwin->w_old_topfill
             && curwin->w_botfill == curwin->w_old_botfill
             && curwin->w_topline == curwin->w_lines[0].wl_lnum)
-           || (type == UPD_INVERTED
+           || (curwin_type == UPD_INVERTED
                && VIsual_active
                && curwin->w_old_cursor_lnum == curwin->w_cursor.lnum
                && curwin->w_old_visual_mode == VIsual_mode
                && (curwin->w_valid & VALID_VIRTCOL)
                && curwin->w_old_curswant == curwin->w_curswant))) {
-    curwin->w_redr_type = type;
+    curwin->w_redr_type = curwin_type;
   }
 
   // Redraw the tab pages line if needed.
@@ -998,6 +1018,9 @@ win_update_start:
   bool scrolled_down = false;   // true when scrolled down when w_topline got smaller a bit
   bool top_to_mod = false;      // redraw above mod_top
 
+  int bot_scroll_start = 999;   // first line that needs to be redrawn due to
+                                // scrolling. only used for EOB
+
   int row;                      // current window row to display
   linenr_T lnum;                // current buffer lnum to display
   int idx;                      // current index in w_lines[]
@@ -1022,7 +1045,9 @@ win_update_start:
   type = wp->w_redr_type;
 
   if (type >= UPD_NOT_VALID) {
+    // TODO(bfredl): should only be implied for CLEAR, not NOT_VALID!
     wp->w_redr_status = true;
+
     wp->w_lines_valid = 0;
   }
 
@@ -1173,6 +1198,7 @@ win_update_start:
       mod_bot = MAXLNUM;
     }
   }
+
   wp->w_redraw_top = 0;  // reset for next time
   wp->w_redraw_bot = 0;
 
@@ -1243,6 +1269,7 @@ win_update_start:
           // If not the last window, delete the lines at the bottom.
           // win_ins_lines may fail when the terminal can't do it.
           win_scroll_lines(wp, 0, i);
+          bot_scroll_start = 0;
           if (wp->w_lines_valid != 0) {
             // Need to update rows that are new, stop at the
             // first one that scrolled down.
@@ -1303,6 +1330,7 @@ win_update_start:
         if (row > 0) {
           win_scroll_lines(wp, 0, -row);
           bot_start = wp->w_grid.rows - row;
+          bot_scroll_start = bot_start;
         }
         if ((row == 0 || bot_start < 999) && wp->w_lines_valid != 0) {
           // Skip the lines (below the deleted lines) that are still
@@ -1680,6 +1708,7 @@ win_update_start:
           // need to redraw until the end of the window.
           // Inserting/deleting lines has no use.
           bot_start = 0;
+          bot_scroll_start = 0;
         } else {
           // Able to count old number of rows: Count new window
           // rows, and may insert/delete lines
@@ -1710,6 +1739,7 @@ win_update_start:
             } else {
               win_scroll_lines(wp, row, xtra_rows);
               bot_start = wp->w_grid.rows + xtra_rows;
+              bot_scroll_start = bot_start;
             }
           } else if (xtra_rows > 0) {
             // May scroll text down.  If there is not enough
@@ -1719,6 +1749,7 @@ win_update_start:
               mod_bot = MAXLNUM;
             } else {
               win_scroll_lines(wp, row + old_rows, xtra_rows);
+              bot_scroll_start = 0;
               if (top_end > row + old_rows) {
                 // Scrolled the part at the top that requires
                 // updating down.
@@ -1908,6 +1939,7 @@ win_update_start:
       wp->w_botline = lnum;
     } else {
       win_draw_end(wp, '@', ' ', true, srow, wp->w_grid.rows, HLF_AT);
+      set_empty_rows(wp, srow);
       wp->w_botline = lnum;
     }
   } else {
@@ -1928,8 +1960,18 @@ win_update_start:
     // Make sure the rest of the screen is blank.
     // write the "eob" character from 'fillchars' to rows that aren't part
     // of the file.
-    win_draw_end(wp, wp->w_p_fcs_chars.eob, ' ', false, row, wp->w_grid.rows,
+    // TODO(bfredl): just keep track of the valid EOB area from last redraw?
+    int lastline = bot_scroll_start;
+    if (mid_end >= row) {
+      lastline = MIN(lastline, mid_start);
+    }
+    if (mod_bot > buf->b_ml.ml_line_count + 1) {
+      lastline = 0;
+    }
+
+    win_draw_end(wp, wp->w_p_fcs_chars.eob, ' ', false, MAX(lastline, row), wp->w_grid.rows,
                  HLF_EOB);
+    set_empty_rows(wp, row);
   }
 
   kvi_destroy(line_providers);
@@ -2041,12 +2083,14 @@ void redraw_buf_later(buf_T *buf, int type)
   }
 }
 
-void redraw_buf_line_later(buf_T *buf,  linenr_T line)
+void redraw_buf_line_later(buf_T *buf, linenr_T line, bool force)
 {
   FOR_ALL_WINDOWS_IN_TAB(wp, curtab) {
-    if (wp->w_buffer == buf
-        && line >= wp->w_topline && line < wp->w_botline) {
-      redrawWinline(wp, line);
+    if (wp->w_buffer == buf) {
+      redrawWinline(wp, MIN(line, buf->b_ml.ml_line_count));
+      if (force && line > buf->b_ml.ml_line_count) {
+        wp->w_redraw_bot = line;
+      }
     }
   }
 }
diff --git a/src/nvim/grid.c b/src/nvim/grid.c
index 63bb945f73..2b73ff895d 100644
--- a/src/nvim/grid.c
+++ b/src/nvim/grid.c
@@ -175,7 +175,7 @@ void grid_put_schar(ScreenGrid *grid, int row, int col, char *schar, int attr)
 {
   assert(put_dirty_row == row);
   size_t off = grid->line_offset[row] + (size_t)col;
-  if (grid->attrs[off] != attr || schar_cmp(grid->chars[off], schar)) {
+  if (grid->attrs[off] != attr || schar_cmp(grid->chars[off], schar) || rdb_flags & RDB_NODELTA) {
     schar_copy(grid->chars[off], schar);
     grid->attrs[off] = attr;
 
@@ -280,7 +280,8 @@ void grid_puts_len(ScreenGrid *grid, char *text, int textlen, int row, int col,
     need_redraw = schar_cmp(grid->chars[off], buf)
                   || (mbyte_cells == 2 && grid->chars[off + 1][0] != 0)
                   || grid->attrs[off] != attr
-                  || exmode_active;
+                  || exmode_active
+                  || rdb_flags & RDB_NODELTA;
 
     if (need_redraw) {
       // When at the end of the text and overwriting a two-cell
@@ -412,8 +413,7 @@ void grid_fill(ScreenGrid *grid, int start_row, int end_row, int start_col, int
     size_t lineoff = grid->line_offset[row];
     for (col = start_col; col < end_col; col++) {
       size_t off = lineoff + (size_t)col;
-      if (schar_cmp(grid->chars[off], sc)
-          || grid->attrs[off] != attr) {
+      if (schar_cmp(grid->chars[off], sc) || grid->attrs[off] != attr || rdb_flags & RDB_NODELTA) {
         schar_copy(grid->chars[off], sc);
         grid->attrs[off] = attr;
         if (dirty_first == INT_MAX) {
@@ -605,7 +605,8 @@ void grid_put_linebuf(ScreenGrid *grid, int row, int coloff, int endcol, int cle
     while (col < clear_width) {
       if (grid->chars[off_to][0] != ' '
           || grid->chars[off_to][1] != NUL
-          || grid->attrs[off_to] != bg_attr) {
+          || grid->attrs[off_to] != bg_attr
+          || rdb_flags & RDB_NODELTA) {
         grid->chars[off_to][0] = ' ';
         grid->chars[off_to][1] = NUL;
         grid->attrs[off_to] = bg_attr;
diff --git a/src/nvim/lua/executor.c b/src/nvim/lua/executor.c
index 09f8c688d8..6063414a02 100644
--- a/src/nvim/lua/executor.c
+++ b/src/nvim/lua/executor.c
@@ -1658,7 +1658,7 @@ void ex_luado(exarg_T *const eap)
   }
   lua_pop(lstate, 1);
   check_cursor();
-  update_screen(UPD_NOT_VALID);
+  redraw_curbuf_later(UPD_NOT_VALID);
 }
 
 /// Run lua file
diff --git a/src/nvim/message.c b/src/nvim/message.c
index c93e825a5d..0b9cbfe474 100644
--- a/src/nvim/message.c
+++ b/src/nvim/message.c
@@ -2053,7 +2053,7 @@ void msg_puts_attr_len(const char *const str, const ptrdiff_t len, int attr)
       overflow = true;
     }
   } else {
-    overflow = msg_scrolled != 0;
+    overflow = msg_scrolled > (p_ch == 0 ? 1 : 0);
   }
 
   if (overflow && !msg_scrolled_ign && strcmp(str, "\r") != 0) {
@@ -2334,7 +2334,7 @@ bool message_filtered(char *msg)
 /// including horizontal separator
 int msg_scrollsize(void)
 {
-  return msg_scrolled + (int)p_ch + 1;
+  return msg_scrolled + (int)p_ch + ((p_ch > 0 || msg_scrolled > 1) ? 1 : 0);
 }
 
 bool msg_use_msgsep(void)
diff --git a/src/nvim/screen.c b/src/nvim/screen.c
index cdfb1e9ee1..1af93f061c 100644
--- a/src/nvim/screen.c
+++ b/src/nvim/screen.c
@@ -155,8 +155,6 @@ void win_draw_end(win_T *wp, int c1, int c2, bool draw_margin, int row, int endr
   } else {
     grid_fill(&wp->w_grid, row, endrow, n, wp->w_grid.cols, c1, c2, attr);
   }
-
-  set_empty_rows(wp, row);
 }
 
 /// Compute the width of the foldcolumn.  Based on 'foldcolumn' and how much
diff --git a/src/nvim/sign.c b/src/nvim/sign.c
index 5ce9ee4546..6f13dd2f06 100644
--- a/src/nvim/sign.c
+++ b/src/nvim/sign.c
@@ -557,7 +557,7 @@ static linenr_T buf_delsign(buf_T *buf, linenr_T atlnum, int id, char *group)
         sign_group_unref((char *)sign->se_group->sg_name);
       }
       xfree(sign);
-      redraw_buf_line_later(buf, lnum);
+      redraw_buf_line_later(buf, lnum, false);
       // Check whether only one sign needs to be deleted
       // If deleting a sign with a specific identifier in a particular
       // group or deleting any sign at a particular line number, delete
@@ -1062,7 +1062,7 @@ static int sign_place(int *sign_id, const char *sign_group, const char *sign_nam
     lnum = buf_change_sign_type(buf, *sign_id, (char *)sign_group, sp->sn_typenr, prio);
   }
   if (lnum > 0) {
-    redraw_buf_line_later(buf, lnum);
+    redraw_buf_line_later(buf, lnum, false);
 
     // When displaying signs in the 'number' column, if the width of the
     // number column is less than 2, then force recomputing the width.
@@ -1093,7 +1093,7 @@ static int sign_unplace(int sign_id, char *sign_group, buf_T *buf, linenr_T atln
     if (lnum == 0) {
       return FAIL;
     }
-    redraw_buf_line_later(buf, lnum);
+    redraw_buf_line_later(buf, lnum, false);
   }
 
   // When all the signs in a buffer are removed, force recomputing the
diff --git a/src/nvim/ui.c b/src/nvim/ui.c
index 09eedcf059..2c9510bf34 100644
--- a/src/nvim/ui.c
+++ b/src/nvim/ui.c
@@ -510,7 +510,7 @@ void ui_flush(void)
     return;
   }
   cmdline_ui_flush();
-  win_ui_flush();
+  win_ui_flush(false);
   msg_ext_ui_flush();
   msg_scroll_flush();
 
diff --git a/src/nvim/ui_compositor.c b/src/nvim/ui_compositor.c
index 9f9a32036c..f23615180e 100644
--- a/src/nvim/ui_compositor.c
+++ b/src/nvim/ui_compositor.c
@@ -590,12 +590,14 @@ static void ui_comp_raw_line(UI *ui, Integer grid, Integer row, Integer startcol
 /// The screen is invalid and will soon be cleared
 ///
 /// Don't redraw floats until screen is cleared
-void ui_comp_set_screen_valid(bool valid)
+bool ui_comp_set_screen_valid(bool valid)
 {
+  bool old_val = valid_screen;
   valid_screen = valid;
   if (!valid) {
     msg_sep_row = -1;
   }
+  return old_val;
 }
 
 static void ui_comp_msg_set_pos(UI *ui, Integer grid, Integer row, Boolean scrolled,
diff --git a/src/nvim/window.c b/src/nvim/window.c
index 2ccbdc10ea..cc20a5fcec 100644
--- a/src/nvim/window.c
+++ b/src/nvim/window.c
@@ -871,8 +871,9 @@ int win_fdccol_count(win_T *wp)
   }
 }
 
-void ui_ext_win_position(win_T *wp)
+void ui_ext_win_position(win_T *wp, bool validate)
 {
+  wp->w_pos_changed = false;
   if (!wp->w_floating) {
     ui_call_win_pos(wp->w_grid_alloc.handle, wp->handle, wp->w_winrow,
                     wp->w_wincol, wp->w_width, wp->w_height);
@@ -910,6 +911,11 @@ void ui_ext_win_position(win_T *wp)
                             grid->handle, row, col, c.focusable,
                             wp->w_grid_alloc.zindex);
     } else {
+      bool valid = (wp->w_redr_type == 0);
+      if (!valid && !validate) {
+        wp->w_pos_changed = true;
+        return;
+      }
       // TODO(bfredl): ideally, compositor should work like any multigrid UI
       // and use standard win_pos events.
       bool east = c.anchor & kFloatAnchorEast;
@@ -923,7 +929,6 @@ void ui_ext_win_position(win_T *wp)
       comp_col = MAX(MIN(comp_col, Columns - wp->w_width_outer), 0);
       wp->w_winrow = comp_row;
       wp->w_wincol = comp_col;
-      bool valid = (wp->w_redr_type == 0);
       ui_comp_put_grid(&wp->w_grid_alloc, comp_row, comp_col,
                        wp->w_height_outer, wp->w_width_outer, valid, false);
       ui_check_cursor_grid(wp->w_grid_alloc.handle);
@@ -2849,12 +2854,12 @@ int win_close(win_T *win, bool free_buf, bool force)
     check_cursor();
   }
 
-  // If last window has a status line now and we don't want one,
-  // remove the status line. Do this before win_equal(), because
-  // it may change the height of a window.
-  last_status(false);
-
   if (!was_floating) {
+    // If last window has a status line now and we don't want one,
+    // remove the status line. Do this before win_equal(), because
+    // it may change the height of a window.
+    last_status(false);
+
     if (!curwin->w_floating && p_ea && (*p_ead == 'b' || *p_ead == dir)) {
       // If the frame of the closed window contains the new current window,
       // only resize that frame.  Otherwise resize all windows.
@@ -2898,7 +2903,10 @@ int win_close(win_T *win, bool free_buf, bool force)
   }
 
   curwin->w_pos_changed = true;
-  redraw_all_later(UPD_NOT_VALID);
+  if (!was_floating) {
+    // TODO(bfredl): how about no?
+    redraw_all_later(UPD_NOT_VALID);
+  }
   return OK;
 }
 
@@ -5413,7 +5421,7 @@ void win_setheight_win(int height, win_T *win)
   if (win->w_floating) {
     win->w_float_config.height = height;
     win_config_float(win, win->w_float_config);
-    redraw_later(win, UPD_NOT_VALID);
+    redraw_later(win, UPD_VALID);
   } else {
     frame_setheight(win->w_frame, height + win->w_hsep_height + win->w_status_height);
 
@@ -6059,6 +6067,9 @@ void win_new_height(win_T *wp, int height)
   wp->w_height = height;
   wp->w_pos_changed = true;
   win_set_inner_size(wp, true);
+  if (wp->w_status_height) {
+    wp->w_redr_status = true;
+  }
 }
 
 void scroll_to_fraction(win_T *wp, int prev_height)
@@ -6196,7 +6207,7 @@ void win_set_inner_size(win_T *wp, bool valid_cursor)
     if (!exiting && valid_cursor) {
       scroll_to_fraction(wp, prev_height);
     }
-    redraw_later(wp, UPD_NOT_VALID);  // UPD_SOME_VALID??
+    redraw_later(wp, UPD_SOME_VALID);
   }
 
   if (width != wp->w_width_inner) {
@@ -6608,7 +6619,6 @@ static void last_status_rec(frame_T *fr, bool statusline, bool is_stl_global)
       wp->w_hsep_height = 0;
       comp_col();
     }
-    redraw_all_later(UPD_SOME_VALID);
   } else {
     // For a column or row frame, recursively call this function for all child frames
     FOR_ALL_FRAMES(fp, fr->fr_child) {
@@ -7336,16 +7346,16 @@ void get_framelayout(const frame_T *fr, list_T *l, bool outer)
   }
 }
 
-void win_ui_flush(void)
+void win_ui_flush(bool validate)
 {
   FOR_ALL_TAB_WINDOWS(tp, wp) {
     if (wp->w_pos_changed && wp->w_grid_alloc.chars != NULL) {
       if (tp == curtab) {
-        ui_ext_win_position(wp);
+        ui_ext_win_position(wp, validate);
       } else {
         ui_call_win_hide(wp->w_grid_alloc.handle);
+        wp->w_pos_changed = false;
       }
-      wp->w_pos_changed = false;
     }
     if (tp == curtab) {
       ui_ext_win_viewport(wp);
diff --git a/test/functional/fixtures/start/nvim-leftpad/lua/async_leftpad.lua b/test/functional/fixtures/start/nvim-leftpad/lua/async_leftpad.lua
index a312572c5b..45226ce24b 100644
--- a/test/functional/fixtures/start/nvim-leftpad/lua/async_leftpad.lua
+++ b/test/functional/fixtures/start/nvim-leftpad/lua/async_leftpad.lua
@@ -1,3 +1,5 @@
 return function (val, res)
-  vim.loop.new_async(function() _G[res] = require'leftpad'(val) end):send()
+  local handle
+  handle = vim.loop.new_async(function() _G[res] = require'leftpad'(val) handle:close() end)
+  handle:send()
 end
diff --git a/test/functional/helpers.lua b/test/functional/helpers.lua
index d672037a1e..eff54b6d4a 100644
--- a/test/functional/helpers.lua
+++ b/test/functional/helpers.lua
@@ -380,10 +380,23 @@ local function remove_args(args, args_rm)
   return new_args
 end
 
+function module.check_close(old_session)
+  local start_time = luv.now()
+  old_session:close()
+  luv.update_time()  -- Update cached value of luv.now() (libuv: uv_now()).
+  local end_time = luv.now()
+  local delta = end_time - start_time
+  if delta > 500 then
+    print("nvim took " .. delta .. " milliseconds to exit after last test\n"..
+          "This indicates a likely problem with the test even if it passed!\n")
+    io.stdout:flush()
+  end
+end
+
 --- @param io_extra used for stdin_fd, see :help ui-option
 function module.spawn(argv, merge, env, keep, io_extra)
   if session and not keep then
-    session:close()
+    module.check_close(session)
   end
 
   local child_stream = ChildProcessStream.spawn(
diff --git a/test/functional/ui/cmdline_spec.lua b/test/functional/ui/cmdline_spec.lua
index 40dee4186b..92eb853686 100644
--- a/test/functional/ui/cmdline_spec.lua
+++ b/test/functional/ui/cmdline_spec.lua
@@ -934,6 +934,15 @@ describe('cmdheight=0', function()
   before_each(function()
     clear()
     screen = Screen.new(25, 5)
+    screen:set_default_attr_ids {
+      [1] = {bold = true, foreground = Screen.colors.Blue};
+      [2] = {bold = true, reverse = true};
+      [3] = {bold = true};
+      [4] = {foreground = Screen.colors.White, background = Screen.colors.Red};
+      [5] = {foreground = Screen.colors.SeaGreen4, bold = true};
+      [6] = {reverse = true};
+      [7] = {background = Screen.colors.Yellow};
+    }
     screen:attach()
   end)
 
@@ -941,9 +950,9 @@ describe('cmdheight=0', function()
     command("set cmdheight=1 noruler laststatus=2")
     screen:expect{grid=[[
       ^                         |
-      ~                        |
-      ~                        |
-      [No Name]                |
+      {1:~                        }|
+      {1:~                        }|
+      {2:[No Name]                }|
                                |
     ]]}
   end)
@@ -952,10 +961,10 @@ describe('cmdheight=0', function()
     command("set cmdheight=0 noruler laststatus=2")
     screen:expect{grid=[[
       ^                         |
-      ~                        |
-      ~                        |
-      ~                        |
-      [No Name]                |
+      {1:~                        }|
+      {1:~                        }|
+      {1:~                        }|
+      {2:[No Name]                }|
     ]]}
   end)
 
@@ -963,10 +972,10 @@ describe('cmdheight=0', function()
     command("set cmdheight=0 ruler laststatus=0")
     screen:expect{grid=[[
       ^                         |
-      ~                        |
-      ~                        |
-      ~                        |
-      ~                        |
+      {1:~                        }|
+      {1:~                        }|
+      {1:~                        }|
+      {1:~                        }|
     ]]}
   end)
 
@@ -975,10 +984,10 @@ describe('cmdheight=0', function()
     feed('i')
     screen:expect{grid=[[
       ^                         |
-      ~                        |
-      ~                        |
-      ~                        |
-      ~                        |
+      {1:~                        }|
+      {1:~                        }|
+      {1:~                        }|
+      {1:~                        }|
     ]], showmode={}}
     feed('<Esc>')
     eq(0, eval('&cmdheight'))
@@ -989,10 +998,10 @@ describe('cmdheight=0', function()
     feed('i')
     screen:expect{grid=[[
       ^                         |
-      ~                        |
-      ~                        |
-      ~                        |
-      ~                        |
+      {1:~                        }|
+      {1:~                        }|
+      {1:~                        }|
+      {1:~                        }|
     ]], showmode={}}
     feed('<Esc>')
     eq(0, eval('&cmdheight'))
@@ -1003,10 +1012,10 @@ describe('cmdheight=0', function()
     feed('i')
     screen:expect{grid=[[
       ^                         |
-      ~                        |
-      ~                        |
-      ~                        |
-      -- INSERT --             |
+      {1:~                        }|
+      {1:~                        }|
+      {1:~                        }|
+      {3:-- INSERT --}             |
     ]]}
     feed('<Esc>')
     eq(1, eval('&cmdheight'))
@@ -1017,19 +1026,19 @@ describe('cmdheight=0', function()
     feed(':')
     screen:expect{grid=[[
                                |
-      ~                        |
-      ~                        |
-      ~                        |
+      {1:~                        }|
+      {1:~                        }|
+      {1:~                        }|
       :^                        |
     ]]}
     eq(0, eval('&cmdheight'))
     feed('<cr>')
     screen:expect{grid=[[
       ^                         |
-      ~                        |
-      ~                        |
-      ~                        |
-      ~                        |
+      {1:~                        }|
+      {1:~                        }|
+      {1:~                        }|
+      {1:~                        }|
     ]], showmode={}}
     eq(0, eval('&cmdheight'))
   end)
@@ -1039,8 +1048,8 @@ describe('cmdheight=0', function()
     feed(':call input("foo >")<cr>')
     screen:expect{grid=[[
                                |
-      ~                        |
-                               |
+      {1:~                        }|
+      {2:                         }|
       :call input("foo >")     |
       foo >^                    |
     ]]}
@@ -1048,10 +1057,10 @@ describe('cmdheight=0', function()
     feed('<cr>')
     screen:expect{grid=[[
       ^                         |
-      ~                        |
-      ~                        |
-      ~                        |
-      ~                        |
+      {1:~                        }|
+      {1:~                        }|
+      {1:~                        }|
+      {1:~                        }|
     ]], showmode={}}
     eq(0, eval('&cmdheight'))
   end)
@@ -1060,35 +1069,35 @@ describe('cmdheight=0', function()
     command("set cmdheight=0 noruler laststatus=3 winbar=foo")
     feed(':split<CR>')
     screen:expect{grid=[[
-                               |
+      {2:                         }|
       :split                   |
-      E36: Not enough room     |
-      Press ENTER or type comma|
-      nd to continue^           |
+      {4:E36: Not enough room}     |
+      {5:Press ENTER or type comma}|
+      {5:nd to continue}^           |
     ]]}
     feed('<CR>')
     screen:expect{grid=[[
-      foo                      |
+      {3:foo                      }|
       ^                         |
-      ~                        |
-      ~                        |
-      [No Name]                |
+      {1:~                        }|
+      {1:~                        }|
+      {2:[No Name]                }|
     ]]}
     feed(':')
     screen:expect{grid=[[
-      foo                      |
+      {3:foo                      }|
                                |
-      ~                        |
-      ~                        |
+      {1:~                        }|
+      {1:~                        }|
       :^                        |
     ]]}
     feed('<Esc>')
     screen:expect{grid=[[
-      foo                      |
+      {3:foo                      }|
       ^                         |
-      ~                        |
-      ~                        |
-      [No Name]                |
+      {1:~                        }|
+      {1:~                        }|
+      {2:[No Name]                }|
     ]], showmode={}}
     eq(0, eval('&cmdheight'))
 
@@ -1100,18 +1109,18 @@ describe('cmdheight=0', function()
     feed('qq')
     screen:expect{grid=[[
       ^                         |
-      ~                        |
-      ~                        |
-      ~                        |
-      ~                        |
+      {1:~                        }|
+      {1:~                        }|
+      {1:~                        }|
+      {1:~                        }|
     ]]}
     feed('q')
     screen:expect{grid=[[
       ^                         |
-      ~                        |
-      ~                        |
-      ~                        |
-      ~                        |
+      {1:~                        }|
+      {1:~                        }|
+      {1:~                        }|
+      {1:~                        }|
     ]], unchanged=true}
   end)
 
@@ -1120,28 +1129,28 @@ describe('cmdheight=0', function()
     feed('ifoo<ESC>')
     screen:expect{grid=[[
       fo^o                      |
-      ~                        |
-      ~                        |
-      ~                        |
-      [No Name] [+]            |
+      {1:~                        }|
+      {1:~                        }|
+      {1:~                        }|
+      {2:[No Name] [+]            }|
     ]]}
 
     feed(':%s/foo/bar/gc<CR>')
     screen:expect{grid=[[
-      foo                      |
-      ~                        |
-      ~                        |
-      ~                        |
-      replace wi...q/l/^E/^Y)?^ |
+      {6:foo}                      |
+      {1:~                        }|
+      {1:~                        }|
+      {1:~                        }|
+      {5:replace wi...q/l/^E/^Y)?}^ |
     ]]}
 
     feed('y')
     screen:expect{grid=[[
       ^bar                      |
-      ~                        |
-      ~                        |
-      ~                        |
-      [No Name] [+]            |
+      {1:~                        }|
+      {1:~                        }|
+      {1:~                        }|
+      {2:[No Name] [+]            }|
     ]]}
 
     assert_alive()
@@ -1152,4 +1161,26 @@ describe('cmdheight=0', function()
     feed('<C-w>+')
     eq(0, eval('&cmdheight'))
   end)
+
+  it("with non-silent mappings with cmdline", function()
+    command("set cmdheight=0")
+    command("map <f3> :nohlsearch<cr>")
+    feed('iaabbaa<esc>/aa<cr>')
+    screen:expect{grid=[[
+      {7:^aa}bb{7:aa}                   |
+      {1:~                        }|
+      {1:~                        }|
+      {1:~                        }|
+      {1:~                        }|
+    ]]}
+
+    feed('<f3>')
+    screen:expect{grid=[[
+      ^aabbaa                   |
+      {1:~                        }|
+      {1:~                        }|
+      {1:~                        }|
+      {1:~                        }|
+    ]]}
+  end)
 end)
diff --git a/test/functional/ui/float_spec.lua b/test/functional/ui/float_spec.lua
index 5967b630f6..a5a664cb3d 100644
--- a/test/functional/ui/float_spec.lua
+++ b/test/functional/ui/float_spec.lua
@@ -8147,6 +8147,366 @@ describe('float window', function()
         ]]}
       end
     end)
+
+    it('it can be resized with messages and cmdheight=0 #20106', function()
+      screen:try_resize(40,9)
+      command 'set cmdheight=0'
+      local buf = meths.create_buf(false,true)
+      local win = meths.open_win(buf, false, {relative='editor', width=40, height=4, anchor='SW', row=9, col=0, style='minimal', border="single", noautocmd=true})
+
+      if multigrid then
+        screen:expect{grid=[[
+        ## grid 1
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+        ## grid 2
+          ^                                        |
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+        ## grid 3
+        ## grid 5
+          {5:┌────────────────────────────────────────┐}|
+          {5:│}{1:                                        }{5:│}|
+          {5:│}{1:                                        }{5:│}|
+          {5:│}{1:                                        }{5:│}|
+          {5:│}{1:                                        }{5:│}|
+          {5:└────────────────────────────────────────┘}|
+        ]], float_pos={
+          [5] = {{id = 1002}, "SW", 1, 9, 0, true, 50};
+        }, win_viewport={
+          [2] = {win = {id = 1000}, topline = 0, botline = 2, curline = 0, curcol = 0, linecount = 1};
+          [5] = {win = {id = 1002}, topline = 0, botline = 2, curline = 0, curcol = 0, linecount = 1};
+        }}
+      else
+        screen:expect{grid=[[
+          ^                                        |
+          {0:~                                       }|
+          {0:~                                       }|
+          {5:┌──────────────────────────────────────┐}|
+          {5:│}{1:                                      }{5:│}|
+          {5:│}{1:                                      }{5:│}|
+          {5:│}{1:                                      }{5:│}|
+          {5:│}{1:                                      }{5:│}|
+          {5:└──────────────────────────────────────┘}|
+        ]]}
+      end
+
+      exec_lua([[
+        local win = ...
+        vim.api.nvim_win_set_height(win, 2)
+        vim.api.nvim_echo({ { "" } }, false, {})
+      ]], win)
+
+      if multigrid then
+        screen:expect{grid=[[
+        ## grid 1
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+        ## grid 2
+          ^                                        |
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+        ## grid 3
+        ## grid 5
+          {5:┌────────────────────────────────────────┐}|
+          {5:│}{1:                                        }{5:│}|
+          {5:│}{1:                                        }{5:│}|
+          {5:└────────────────────────────────────────┘}|
+        ]], float_pos={
+          [5] = {{id = 1002}, "SW", 1, 9, 0, true, 50};
+        }, win_viewport={
+          [2] = {win = {id = 1000}, topline = 0, botline = 2, curline = 0, curcol = 0, linecount = 1};
+          [5] = {win = {id = 1002}, topline = 0, botline = 2, curline = 0, curcol = 0, linecount = 1};
+        }}
+      else
+        screen:expect{grid=[[
+          ^                                        |
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {5:┌──────────────────────────────────────┐}|
+          {5:│}{1:                                      }{5:│}|
+          {5:│}{1:                                      }{5:│}|
+          {5:└──────────────────────────────────────┘}|
+        ]]}
+
+      end
+
+      meths.win_close(win, true)
+      if multigrid then
+        screen:expect{grid=[[
+        ## grid 1
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+        ## grid 2
+          ^                                        |
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+        ## grid 3
+        ]], win_viewport={
+          [2] = {win = {id = 1000}, topline = 0, botline = 2, curline = 0, curcol = 0, linecount = 1};
+        }}
+      else
+        screen:expect{grid=[[
+          ^                                        |
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+        ]]}
+      end
+    end)
+
+    it('it can be resized with messages and cmdheight=1', function()
+      screen:try_resize(40,9)
+      local buf = meths.create_buf(false,true)
+      local win = meths.open_win(buf, false, {relative='editor', width=40, height=4, anchor='SW', row=8, col=0, style='minimal', border="single", noautocmd=true})
+
+      if multigrid then
+        screen:expect{grid=[[
+        ## grid 1
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [3:----------------------------------------]|
+        ## grid 2
+          ^                                        |
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+        ## grid 3
+                                                  |
+        ## grid 5
+          {5:┌────────────────────────────────────────┐}|
+          {5:│}{1:                                        }{5:│}|
+          {5:│}{1:                                        }{5:│}|
+          {5:│}{1:                                        }{5:│}|
+          {5:│}{1:                                        }{5:│}|
+          {5:└────────────────────────────────────────┘}|
+        ]], float_pos={
+          [5] = {{id = 1002}, "SW", 1, 8, 0, true, 50};
+        }, win_viewport={
+          [2] = {win = {id = 1000}, topline = 0, botline = 2, curline = 0, curcol = 0, linecount = 1};
+          [5] = {win = {id = 1002}, topline = 0, botline = 2, curline = 0, curcol = 0, linecount = 1};
+        }}
+      else
+        screen:expect{grid=[[
+          ^                                        |
+          {0:~                                       }|
+          {5:┌──────────────────────────────────────┐}|
+          {5:│}{1:                                      }{5:│}|
+          {5:│}{1:                                      }{5:│}|
+          {5:│}{1:                                      }{5:│}|
+          {5:│}{1:                                      }{5:│}|
+          {5:└──────────────────────────────────────┘}|
+                                                  |
+        ]]}
+      end
+
+      exec_lua([[
+        -- echo prompt is blocking, so schedule
+        local win = ...
+        vim.schedule(function()
+          vim.api.nvim_win_set_height(win, 2)
+          vim.api.nvim_echo({ { "\n" } }, false, {})
+        end)
+      ]], win)
+
+      if multigrid then
+        screen:expect{grid=[[
+        ## grid 1
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [3:----------------------------------------]|
+          [3:----------------------------------------]|
+        ## grid 2
+                                                  |
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+        ## grid 3
+                                                  |
+          {8:Press ENTER or type command to continue}^ |
+        ## grid 5
+          {5:┌────────────────────────────────────────┐}|
+          {5:│}{1:                                        }{5:│}|
+          {5:│}{1:                                        }{5:│}|
+          {5:│}{1:                                        }{5:│}|
+          {5:│}{1:                                        }{5:│}|
+          {5:└────────────────────────────────────────┘}|
+        ]], float_pos={
+          [5] = {{id = 1002}, "SW", 1, 8, 0, true, 50};
+        }, win_viewport={
+          [2] = {win = {id = 1000}, topline = 0, botline = 2, curline = 0, curcol = 0, linecount = 1};
+          [5] = {win = {id = 1002}, topline = 0, botline = 2, curline = 0, curcol = 0, linecount = 1};
+        }}
+      else
+        screen:expect{grid=[[
+                                                  |
+          {0:~                                       }|
+          {5:┌──────────────────────────────────────┐}|
+          {5:│}{1:                                      }{5:│}|
+          {5:│}{1:                                      }{5:│}|
+          {5:│}{1:                                      }{5:│}|
+          {4:                                        }|
+                                                  |
+          {8:Press ENTER or type command to continue}^ |
+        ]]}
+      end
+
+      feed('<cr>')
+      if multigrid then
+        screen:expect{grid=[[
+        ## grid 1
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [3:----------------------------------------]|
+        ## grid 2
+          ^                                        |
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+        ## grid 3
+                                                  |
+        ## grid 5
+          {5:┌────────────────────────────────────────┐}|
+          {5:│}{1:                                        }{5:│}|
+          {5:│}{1:                                        }{5:│}|
+          {5:└────────────────────────────────────────┘}|
+        ]], float_pos={
+          [5] = {{id = 1002}, "SW", 1, 8, 0, true, 50};
+        }, win_viewport={
+          [2] = {win = {id = 1000}, topline = 0, botline = 2, curline = 0, curcol = 0, linecount = 1};
+          [5] = {win = {id = 1002}, topline = 0, botline = 2, curline = 0, curcol = 0, linecount = 1};
+        }}
+      else
+        screen:expect{grid=[[
+          ^                                        |
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {5:┌──────────────────────────────────────┐}|
+          {5:│}{1:                                      }{5:│}|
+          {5:│}{1:                                      }{5:│}|
+          {5:└──────────────────────────────────────┘}|
+                                                  |
+        ]]}
+      end
+
+      meths.win_close(win, true)
+      if multigrid then
+        screen:expect{grid=[[
+        ## grid 1
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [3:----------------------------------------]|
+        ## grid 2
+          ^                                        |
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+        ## grid 3
+                                                  |
+        ]], win_viewport={
+          [2] = {win = {id = 1000}, topline = 0, botline = 2, curline = 0, curcol = 0, linecount = 1};
+        }}
+
+      else
+        screen:expect{grid=[[
+          ^                                        |
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+                                                  |
+        ]]}
+      end
+    end)
   end
 
   describe('with ext_multigrid', function()
diff --git a/test/functional/ui/syntax_conceal_spec.lua b/test/functional/ui/syntax_conceal_spec.lua
index f790597140..e8798ddd93 100644
--- a/test/functional/ui/syntax_conceal_spec.lua
+++ b/test/functional/ui/syntax_conceal_spec.lua
@@ -947,7 +947,7 @@ describe('Screen', function()
       {0:~                                                    }|
                                                            |
     ]]}
-    eq({{2, 0, {{'c', 0, 3}}}}, grid_lines)
+    eq({{2, 0, {{'c', 0, 3}, {' ', 0, 50}}}, {3, 0, {{' ', 0, 53}}}}, grid_lines)
   end)
 
   it('K_EVENT should not cause extra redraws with concealcursor #13196', function()
@@ -994,10 +994,11 @@ describe('Screen', function()
       {0:~                                                    }|
                                                            |
     ]]}
-    eq({{2, 0, {{'c', 0, 3}}}}, grid_lines)
+    eq({{2, 0, {{'c', 0, 3}, {' ', 0, 50}}}}, grid_lines)
+    grid_lines = {}
     poke_eventloop()  -- causes K_EVENT key
     screen:expect_unchanged()
-    eq({{2, 0, {{'c', 0, 3}}}}, grid_lines)
+    eq({}, grid_lines) -- no redraw was done
   end)
 
   -- Copy of Test_cursor_column_in_concealed_line_after_window_scroll in