vim-patch:9.0.0114: the command line takes up space even when not used

Problem:    The command line takes up space even when not used.
Solution:   Allow for 'cmdheight' to be set to zero. (Shougo Matsushita,
            closes vim/vim#10675, closes vim/vim#940)
f39cfb7262

Omit win_redr_ruler() change: winbar may still need redraw.
Omit win_update() changes: Nvim doesn't use `Rows` there.
Omit redraw_asap(): removed.

src/nvim/ex_cmds.c

@@ -3669,7 +3669,7 @@ static int do_sub(exarg_T *eap, proftime_T timeout, long cmdpreview_ns, handle_T
     }
   }
 
-  bool cmdheight0 = !ui_has_messages();
+  const bool cmdheight0 = !ui_has_messages();
   if (cmdheight0) {
     // If cmdheight is 0, cmdheight must be set to 1 when we enter command line.
     set_option_value("ch", 1L, NULL, 0);

src/nvim/ex_getln.c

@@ -689,7 +689,7 @@ static void finish_incsearch_highlighting(int gotesc, incsearch_state_T *s, bool
 /// @param init_ccline  clear ccline first
 static uint8_t *command_line_enter(int firstc, long count, int indent, bool init_ccline)
 {
-  bool cmdheight0 = !ui_has_messages();
+  const bool cmdheight0 = !ui_has_messages();
 
   if (cmdheight0) {
     // If cmdheight is 0, cmdheight must be set to 1 when we enter command line.
@@ -993,7 +993,6 @@ theend:
   if (cmdheight0) {
     // Restore cmdheight
     set_option_value("ch", 0L, NULL, 0);
-
     // Redraw is needed for command line completion
     redraw_all_later(CLEAR);
   }

src/nvim/message.c

@@ -1390,7 +1390,7 @@ void msg_start(void)
     need_fileinfo = false;
   }
 
-  bool no_msg_area = !ui_has_messages();
+  const bool no_msg_area = !ui_has_messages();
 
   if (need_clr_eos || (no_msg_area && redrawing_cmdline)) {
     // Halfway an ":echo" command and getting an (error) message: clear

src/nvim/ops.c

@@ -893,7 +893,7 @@ int do_record(int c)
 {
   char_u *p;
   static int regname;
-  static bool change_cmdheight = false;
+  static bool changed_cmdheight = false;
   yankreg_T *old_y_previous;
   int retval;
 
@@ -907,13 +907,15 @@ int do_record(int c)
       showmode();
       regname = c;
       retval = OK;
+
       if (!ui_has_messages()) {
         // Enable macro indicator temporary
         set_option_value("ch", 1L, NULL, 0);
         update_screen(VALID);
 
-        change_cmdheight = true;
+        changed_cmdheight = true;
       }
+
       apply_autocmds(EVENT_RECORDINGENTER, NULL, NULL, false, curbuf);
     }
   } else {  // stop recording
@@ -936,15 +938,6 @@ int do_record(int c)
     (void)tv_dict_add_str(dict, S_LEN("regname"), buf);
     tv_dict_set_keys_readonly(dict);
 
-    if (change_cmdheight) {
-      // Restore cmdheight
-      set_option_value("ch", 0L, NULL, 0);
-
-      redraw_all_later(CLEAR);
-
-      change_cmdheight = false;
-    }
-
     // Get the recorded key hits.  K_SPECIAL will be escaped, this
     // needs to be removed again to put it in a register.  exec_reg then
     // adds the escaping back later.
@@ -968,6 +961,12 @@ int do_record(int c)
 
       y_previous = old_y_previous;
     }
+
+    if (changed_cmdheight) {
+      // Restore cmdheight
+      set_option_value("ch", 0L, NULL, 0);
+      redraw_all_later(CLEAR);
+    }
   }
   return retval;
 }

src/nvim/screen.c

@@ -6501,7 +6501,7 @@ static void win_redr_ruler(win_T *wp, bool always)
   bool is_stl_global = global_stl_height() > 0;
   static bool did_show_ext_ruler = false;
 
-  // If 'ruler' off or redrawing disabled, don't do anything
+  // If 'ruler' off, don't do anything
   if (!p_ru) {
     return;
   }

src/nvim/testdir/test_messages.vim

@@ -316,4 +316,51 @@ func Test_fileinfo_after_echo()
   call delete('b.txt')
 endfunc
 
+func Test_cmdheight_zero()
+  set cmdheight=0
+  set showcmd
+  redraw!
+
+  echo 'test echo'
+  call assert_equal(116, screenchar(&lines, 1))
+  redraw!
+
+  echomsg 'test echomsg'
+  call assert_equal(116, screenchar(&lines, 1))
+  redraw!
+
+  call feedkeys(":ls\<CR>", "xt")
+  call assert_equal(':ls', Screenline(&lines - 1))
+  redraw!
+
+  let char = getchar(0)
+  call assert_match(char, 0)
+
+  " Check change/restore cmdheight when macro
+  call feedkeys("qa", "xt")
+  call assert_equal(&cmdheight, 1)
+  call feedkeys("q", "xt")
+  call assert_equal(&cmdheight, 0)
+
+  call setline(1, 'somestring')
+  call feedkeys("y", "n")
+  %s/somestring/otherstring/gc
+  call assert_equal(getline(1), 'otherstring')
+
+  call feedkeys("g\<C-g>", "xt")
+  call assert_match(
+        \ 'Col 1 of 11; Line 1 of 1; Word 1 of 1',
+        \ Screenline(&lines))
+
+  " Check split behavior
+  for i in range(1, 10)
+    split
+  endfor
+  only
+  call assert_equal(&cmdheight, 0)
+
+  set cmdheight&
+  set showcmd&
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab

src/nvim/testdir/test_window_cmd.vim

@@ -1390,11 +1390,9 @@ func Test_win_move_statusline()
     call assert_equal(h0, winheight(0))
     call assert_equal(1, &cmdheight)
   endfor
-  " Nvim supports cmdheight=0
+  " supports cmdheight=0
   set cmdheight=0
   call assert_true(win_move_statusline(0, 1))
-  "call assert_equal(h0, winheight(0))
-  "call assert_equal(1, &cmdheight)
   call assert_equal(h0 + 1, winheight(0))
   call assert_equal(0, &cmdheight)
   set cmdheight&

src/nvim/window.c

@@ -5555,7 +5555,6 @@ static void frame_setheight(frame_T *curfrp, int height)
   }
 
   if (curfrp->fr_parent == NULL) {
-    // topframe: can only change the command line
     if (height > ROWS_AVAIL) {
       // If height is greater than the available space, try to create space for
       // the frame by reducing 'cmdheight' if possible, while making sure