feat: cmdheight=0 #16251

Fix https://github.com/neovim/neovim/issues/1004

Limitation: All outputs need hit-enter prompt.

Related:
https://github.com/neovim/neovim/pull/6732
https://github.com/neovim/neovim/pull/4382

13 files changed, 247 insertions, 36 deletions

diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index c9f978471f..5d227a702c 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -1320,6 +1320,9 @@ A jump table for the options with a short description can be found at |Q_op|.
 	The value of this option is stored with the tab page, so that each tab
 	page can have a different value.
 
+	When 'cmdheight' is zero, it disables echo area and all outputs need
+	|hit-enter| prompt.
+
 						*'cmdwinheight'* *'cwh'*
 'cmdwinheight' 'cwh'	number	(default 7)
 			global
@@ -4817,9 +4820,11 @@ A jump table for the options with a short description can be found at |Q_op|.
 		45%	relative position in the file
 	If 'rulerformat' is set, it will determine the contents of the ruler.
 	Each window has its own ruler.  If a window has a status line, the
-	ruler is shown there.  Otherwise it is shown in the last line of the
-	screen.  If the statusline is given by 'statusline' (i.e. not empty),
-	this option takes precedence over 'ruler' and 'rulerformat'
+	ruler is shown there.  If a window doesn't have a status line and
+	'cmdheight' is 0, the ruler is not shown.  Otherwise it is shown in
+	the last line of the screen.  If the statusline is given by
+	'statusline' (i.e. not empty), this option takes precedence over
+	'ruler' and 'rulerformat'.
 	If the number of characters displayed is different from the number of
 	bytes in the text (e.g., for a TAB or a multibyte character), both
 	the text column (byte number) and the screen column are shown,
@@ -5525,6 +5530,7 @@ A jump table for the options with a short description can be found at |Q_op|.
 			global
 	Show (partial) command in the last line of the screen.  Set this
 	option off if your terminal is slow.
+	The option is disabled if 'cmdheight' is 0.
 	In Visual mode the size of the selected area is shown:
 	- When selecting characters within a line, the number of characters.
 	  If the number of bytes is different it is also displayed: "2-6"
@@ -5571,6 +5577,7 @@ A jump table for the options with a short description can be found at |Q_op|.
 			global
 	If in Insert, Replace or Visual mode put a message on the last line.
 	The |hl-ModeMsg| highlight group determines the highlighting.
+	The option is disabled if 'cmdheight' is 0.
 
 						*'showtabline'* *'stal'*
 'showtabline' 'stal'	number	(default 1)
diff --git a/src/nvim/ex_getln.c b/src/nvim/ex_getln.c
index 94ce1ec495..46cc4b5c7e 100644
--- a/src/nvim/ex_getln.c
+++ b/src/nvim/ex_getln.c
@@ -108,11 +108,9 @@ typedef enum {
   kCmdRedrawAll,
 } CmdRedraw;
 
-/*
- * Variables shared between getcmdline(), redrawcmdline() and others.
- * These need to be saved when using CTRL-R |, that's why they are in a
- * structure.
- */
+// Variables shared between getcmdline(), redrawcmdline() and others.
+// These need to be saved when using CTRL-R |, that's why they are in a
+// structure.
 struct cmdline_info {
   char_u *cmdbuff;         // pointer to command line buffer
   int cmdbufflen;               // length of cmdbuff
@@ -139,6 +137,7 @@ struct cmdline_info {
   bool special_shift;           ///< shift of last putcmdline char
   CmdRedraw redraw_state;       ///< needed redraw for external cmdline
 };
+
 /// Last value of prompt_id, incremented when doing new prompt
 static unsigned last_prompt_id = 0;
 
@@ -689,6 +688,14 @@ 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 = p_ch < 1 && !ui_has(kUIMessages) && vpeekc() == NUL;
+
+  if (cmdheight0) {
+    // If cmdheight is 0, cmdheight must be set to 1 when we enter command line.
+    set_option_value("ch", 1L, NULL, 0);
+    redraw_statuslines();
+  }
+
   // can be invoked recursively, identify each level
   static int cmdline_level = 0;
   cmdline_level++;
@@ -976,6 +983,11 @@ theend:
     ccline.cmdbuff = NULL;
   }
 
+  if (cmdheight0) {
+    // Restore cmdheight
+    set_option_value("ch", 0L, NULL, 0);
+  }
+
   return p;
 }
 
@@ -2670,6 +2682,12 @@ char *getcmdline_prompt(const char firstc, const char *const prompt, const int a
   return ret;
 }
 
+// Return current cmdline prompt
+char_u *get_cmdprompt(void)
+{
+  return ccline.cmdprompt;
+}
+
 /*
  * Return TRUE when the text must not be changed and we can't switch to
  * another window or buffer.  Used when editing the command line etc.
@@ -3777,7 +3795,7 @@ void redrawcmd(void)
   msg_no_more = TRUE;
   draw_cmdline(0, ccline.cmdlen);
   msg_clr_eos();
-  msg_no_more = FALSE;
+  msg_no_more = false;
 
   ccline.cmdspos = cmd_screencol(ccline.cmdpos);
 
diff --git a/src/nvim/message.c b/src/nvim/message.c
index f250f6de58..23ceb0ba4c 100644
--- a/src/nvim/message.c
+++ b/src/nvim/message.c
@@ -18,6 +18,7 @@
 #include "nvim/eval.h"
 #include "nvim/ex_docmd.h"
 #include "nvim/ex_eval.h"
+#include "nvim/ex_getln.h"
 #include "nvim/fileio.h"
 #include "nvim/func_attr.h"
 #include "nvim/garray.h"
@@ -163,6 +164,7 @@ void msg_grid_validate(void)
 {
   grid_assign_handle(&msg_grid);
   bool should_alloc = msg_use_grid();
+  int max_rows = Rows - p_ch;
   if (should_alloc && (msg_grid.rows != Rows || msg_grid.cols != Columns
                        || !msg_grid.chars)) {
     // TODO(bfredl): eventually should be set to "invalid". I e all callers
@@ -174,7 +176,7 @@ void msg_grid_validate(void)
     msg_grid.dirty_col = xcalloc(Rows, sizeof(*msg_grid.dirty_col));
 
     // Tricky: allow resize while pager is active
-    int pos = msg_scrolled ? msg_grid_pos : Rows - p_ch;
+    int pos = msg_scrolled ? msg_grid_pos : max_rows;
     ui_comp_put_grid(&msg_grid, pos, 0, msg_grid.rows, msg_grid.cols,
                      false, true);
     ui_call_grid_resize(msg_grid.handle, msg_grid.cols, msg_grid.rows);
@@ -184,7 +186,7 @@ void msg_grid_validate(void)
     msg_grid.focusable = false;
     msg_grid_adj.target = &msg_grid;
     if (!msg_scrolled) {
-      msg_grid_set_pos(Rows - p_ch, false);
+      msg_grid_set_pos(max_rows, false);
     }
   } else if (!should_alloc && msg_grid.chars) {
     ui_comp_remove_grid(&msg_grid);
@@ -195,8 +197,8 @@ void msg_grid_validate(void)
     msg_grid_adj.row_offset = 0;
     msg_grid_adj.target = &default_grid;
     redraw_cmdline = true;
-  } else if (msg_grid.chars && !msg_scrolled && msg_grid_pos != Rows - p_ch) {
-    msg_grid_set_pos(Rows - p_ch, false);
+  } else if (msg_grid.chars && !msg_scrolled && msg_grid_pos != max_rows) {
+    msg_grid_set_pos(max_rows, false);
   }
 
   if (msg_grid.chars && cmdline_row < msg_grid_pos) {
@@ -1386,7 +1388,9 @@ void msg_start(void)
     need_fileinfo = false;
   }
 
-  if (need_clr_eos) {
+  bool no_msg_area = !ui_has(kUIMessages) && p_ch < 1;
+
+  if (need_clr_eos || (no_msg_area && redrawing_cmdline)) {
     // Halfway an ":echo" command and getting an (error) message: clear
     // any text from the command.
     need_clr_eos = false;
@@ -1395,10 +1399,11 @@ void msg_start(void)
 
   if (!msg_scroll && full_screen) {     // overwrite last message
     msg_row = cmdline_row;
-    msg_col =
-      cmdmsg_rl ? Columns - 1 :
-      0;
-  } else if (msg_didout) {                // start message on next line
+    msg_col = cmdmsg_rl ? Columns - 1 : 0;
+    if (no_msg_area && get_cmdprompt() == NULL) {
+      msg_row -= 1;
+    }
+  } else if (msg_didout || no_msg_area) {  // start message on next line
     msg_putchar('\n');
     did_return = true;
     cmdline_row = msg_row;
@@ -3055,7 +3060,7 @@ void repeat_message(void)
 /// Skip this when ":silent" was used, no need to clear for redirection.
 void msg_clr_eos(void)
 {
-  if (msg_silent == 0) {
+  if (msg_silent == 0 && p_ch > 0) {
     msg_clr_eos_force();
   }
 }
@@ -3077,10 +3082,11 @@ void msg_clr_eos_force(void)
     msg_row = msg_grid_pos;
   }
 
-  grid_fill(&msg_grid_adj, msg_row, msg_row + 1, msg_startcol, msg_endcol, ' ',
-            ' ', HL_ATTR(HLF_MSG));
-  grid_fill(&msg_grid_adj, msg_row + 1, Rows, 0, Columns, ' ', ' ',
-            HL_ATTR(HLF_MSG));
+  grid_fill(&msg_grid_adj, msg_row, msg_row + 1, msg_startcol, msg_endcol,
+            ' ', ' ', HL_ATTR(HLF_MSG));
+  if (p_ch > 0) {
+    grid_fill(&msg_grid_adj, msg_row + 1, Rows, 0, Columns, ' ', ' ', HL_ATTR(HLF_MSG));
+  }
 
   redraw_cmdline = true;  // overwritten the command line
   if (msg_row < Rows - 1 || msg_col == (cmdmsg_rl ? Columns : 0)) {
diff --git a/src/nvim/normal.c b/src/nvim/normal.c
index 3603e11f5d..87a9e1e765 100644
--- a/src/nvim/normal.c
+++ b/src/nvim/normal.c
@@ -2747,6 +2747,10 @@ void pop_showcmd(void)
 
 static void display_showcmd(void)
 {
+  if (p_ch < 1 && !ui_has(kUIMessages)) {
+    return;
+  }
+
   int len;
   len = (int)STRLEN(showcmd_buf);
   showcmd_is_clear = (len == 0);
diff --git a/src/nvim/ops.c b/src/nvim/ops.c
index 7dcf4c433e..0f202b2fd3 100644
--- a/src/nvim/ops.c
+++ b/src/nvim/ops.c
@@ -6041,6 +6041,10 @@ void cursor_pos_info(dict_T *dict)
       // Don't shorten this message, the user asked for it.
       p = p_shm;
       p_shm = (char_u *)"";
+      if (p_ch < 1) {
+        msg_start();
+        msg_scroll = true;
+      }
       msg((char *)IObuff);
       p_shm = p;
     }
diff --git a/src/nvim/option.c b/src/nvim/option.c
index 35736fd5eb..ca9c7468cf 100644
--- a/src/nvim/option.c
+++ b/src/nvim/option.c
@@ -4365,7 +4365,7 @@ static char *set_num_option(int opt_idx, char_u *varp, long value, char *errbuf,
       errmsg = e_positive;
     }
   } else if (pp == &p_ch) {
-    int minval = ui_has(kUIMessages) ? 0 : 1;
+    int minval = 0;
     if (value < minval) {
       errmsg = e_positive;
     }
diff --git a/src/nvim/screen.c b/src/nvim/screen.c
index 4142409ee0..2ee7cd44f7 100644
--- a/src/nvim/screen.c
+++ b/src/nvim/screen.c
@@ -6132,6 +6132,10 @@ void unshowmode(bool force)
 // Clear the mode message.
 void clearmode(void)
 {
+  if (p_ch <= 0 && !ui_has(kUIMessages)) {
+    return;
+  }
+
   const int save_msg_row = msg_row;
   const int save_msg_col = msg_col;
 
@@ -6500,7 +6504,6 @@ static void win_redr_ruler(win_T *wp, bool always)
 
   if (*p_ruf) {
     int save_called_emsg = called_emsg;
-
     called_emsg = false;
     win_redr_custom(wp, false, true);
     if (called_emsg) {
@@ -6558,6 +6561,10 @@ static void win_redr_ruler(win_T *wp, bool always)
       off = 0;
     }
 
+    if (!part_of_status && p_ch < 1 && !ui_has(kUIMessages)) {
+      return;
+    }
+
     // In list mode virtcol needs to be recomputed
     colnr_T virtcol = wp->w_virtcol;
     if (wp->w_p_list && wp->w_p_lcs_chars.tab1 == NUL) {
@@ -6770,7 +6777,7 @@ void screen_resize(int width, int height)
   Columns = width;
   check_shellsize();
   int max_p_ch = Rows - min_rows() + 1;
-  if (!ui_has(kUIMessages) && p_ch > max_p_ch) {
+  if (!ui_has(kUIMessages) && p_ch > 0 && p_ch > max_p_ch) {
     p_ch = max_p_ch ? max_p_ch : 1;
   }
   height = Rows;
diff --git a/src/nvim/testdir/test_window_cmd.vim b/src/nvim/testdir/test_window_cmd.vim
index 798122dc5d..0fe5fc59eb 100644
--- a/src/nvim/testdir/test_window_cmd.vim
+++ b/src/nvim/testdir/test_window_cmd.vim
@@ -887,6 +887,7 @@ func Test_floatwin_splitmove()
 endfunc
 
 func Test_window_resize()
+  throw 'Skipped: Nvim supports cmdheight=0'
   " Vertical :resize (absolute, relative, min and max size).
   vsplit
   vert resize 8
@@ -1028,9 +1029,14 @@ func Test_win_move_statusline()
     call assert_equal(h0, winheight(0))
     call assert_equal(1, &cmdheight)
   endfor
+  " Nvim 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, winheight(0))
+  "call assert_equal(1, &cmdheight)
+  call assert_equal(h0 + 1, winheight(0))
+  call assert_equal(0, &cmdheight)
+  set cmdheight&
   " check win_move_statusline from bottom window on top window ID
   let id = win_getid(1)
   for offset in range(5)
diff --git a/src/nvim/window.c b/src/nvim/window.c
index e09a7cd97e..e08db2261b 100644
--- a/src/nvim/window.c
+++ b/src/nvim/window.c
@@ -907,7 +907,7 @@ void ui_ext_win_position(win_T *wp)
       int comp_col = (int)col - (east ? wp->w_width_outer : 0);
       comp_row += grid->comp_row;
       comp_col += grid->comp_col;
-      comp_row = MAX(MIN(comp_row, Rows - wp->w_height_outer - 1), 0);
+      comp_row = MAX(MIN(comp_row, Rows - wp->w_height_outer - (p_ch > 0 ? 1 : 0)), 0);
       comp_col = MAX(MIN(comp_col, Columns - wp->w_width_outer), 0);
       wp->w_winrow = comp_row;
       wp->w_wincol = comp_col;
@@ -1144,6 +1144,9 @@ int win_split_ins(int size, int flags, win_T *new_wp, int dir)
     if (flags & WSP_ROOM) {
       needed += p_wh - wmh1 + oldwin->w_winbar_height;
     }
+    if (p_ch < 1) {
+      needed += 1;  // Adjust for cmdheight=0.
+    }
     if (flags & (WSP_BOT | WSP_TOP)) {
       minheight = frame_minheight(topframe, NOWIN) + need_status;
       available = topframe->fr_height;
@@ -5501,7 +5504,7 @@ void win_setheight_win(int height, win_T *win)
       }
     }
     cmdline_row = row;
-    p_ch = MAX(Rows - cmdline_row, ui_has(kUIMessages) ? 0 : 1);
+    p_ch = MAX(Rows - cmdline_row, 0);
     curtab->tp_ch_used = p_ch;
     msg_row = row;
     msg_col = 0;
@@ -5949,9 +5952,7 @@ void win_drag_status_line(win_T *dragwin, int offset)
     up = false;
     // Only dragging the last status line can reduce p_ch.
     room = Rows - cmdline_row;
-    if (curfr->fr_next == NULL) {
-      room -= 1;
-    } else {
+    if (curfr->fr_next != NULL) {
       room -= p_ch + global_stl_height();
     }
     if (room < 0) {
@@ -6008,7 +6009,7 @@ void win_drag_status_line(win_T *dragwin, int offset)
     clear_cmdline = true;
   }
   cmdline_row = row;
-  p_ch = MAX(Rows - cmdline_row, ui_has(kUIMessages) ? 0 : 1);
+  p_ch = MAX(Rows - cmdline_row, 0);
   curtab->tp_ch_used = p_ch;
   redraw_all_later(SOME_VALID);
   showmode();
diff --git a/test/functional/options/num_options_spec.lua b/test/functional/options/num_options_spec.lua
index 4754c14f5b..f343e2da75 100644
--- a/test/functional/options/num_options_spec.lua
+++ b/test/functional/options/num_options_spec.lua
@@ -54,7 +54,7 @@ describe(':set validation', function()
     should_fail('iminsert', 3, 'E474')
     should_fail('imsearch', 3, 'E474')
     should_fail('titlelen', -1, 'E487')
-    should_fail('cmdheight', 0, 'E487')
+    should_fail('cmdheight', -1, 'E487')
     should_fail('updatecount', -1, 'E487')
     should_fail('textwidth', -1, 'E487')
     should_fail('tabstop', 0, 'E487')
diff --git a/test/functional/ui/cmdline_spec.lua b/test/functional/ui/cmdline_spec.lua
index 3b273fd229..0aee34d367 100644
--- a/test/functional/ui/cmdline_spec.lua
+++ b/test/functional/ui/cmdline_spec.lua
@@ -5,6 +5,8 @@ local source = helpers.source
 local command = helpers.command
 local assert_alive = helpers.assert_alive
 local uname = helpers.uname
+local eval = helpers.eval
+local eq = helpers.eq
 
 local function new_screen(opt)
   local screen = Screen.new(25, 5)
@@ -858,3 +860,156 @@ describe("cmdline height", function()
     assert_alive()
   end)
 end)
+
+describe('cmdheight=0', function()
+  local screen
+  before_each(function()
+    clear()
+    screen = Screen.new(25, 5)
+    screen:attach()
+  end)
+
+  it("with cmdheight=1 noruler laststatus=2", function()
+    command("set cmdheight=1 noruler laststatus=2")
+    screen:expect{grid=[[
+      ^                         |
+      ~                        |
+      ~                        |
+      [No Name]                |
+                               |
+    ]]}
+  end)
+
+  it("with cmdheight=0 noruler laststatus=2", function()
+    command("set cmdheight=0 noruler laststatus=2")
+    screen:expect{grid=[[
+      ^                         |
+      ~                        |
+      ~                        |
+      ~                        |
+      [No Name]                |
+    ]]}
+  end)
+
+  it("with cmdheight=0 ruler laststatus=0", function()
+    command("set cmdheight=0 ruler laststatus=0")
+    screen:expect{grid=[[
+      ^                         |
+      ~                        |
+      ~                        |
+      ~                        |
+      ~                        |
+    ]]}
+  end)
+
+  it("with cmdheight=0 ruler laststatus=0", function()
+    command("set cmdheight=0 noruler laststatus=0 showmode")
+    feed('i')
+    screen:expect{grid=[[
+      ^                         |
+      ~                        |
+      ~                        |
+      ~                        |
+      ~                        |
+    ]], showmode={}}
+    feed('<Esc>')
+    eq(0, eval('&cmdheight'))
+  end)
+
+  it("with showmode", function()
+    command("set cmdheight=1 noruler laststatus=0 showmode")
+    feed('i')
+    screen:expect{grid=[[
+      ^                         |
+      ~                        |
+      ~                        |
+      ~                        |
+      -- INSERT --             |
+    ]]}
+    feed('<Esc>')
+    eq(1, eval('&cmdheight'))
+  end)
+
+  it("when using command line", function()
+    command("set cmdheight=0 noruler laststatus=0")
+    feed(':')
+    screen:expect{grid=[[
+                               |
+      ~                        |
+      ~                        |
+      ~                        |
+      :^                        |
+    ]]}
+    eq(1, eval('&cmdheight'))
+    feed('<cr>')
+    screen:expect{grid=[[
+      ^                         |
+      ~                        |
+      ~                        |
+      ~                        |
+      ~                        |
+    ]], showmode={}}
+    eq(0, eval('&cmdheight'))
+  end)
+
+  it("when using input()", function()
+    command("set cmdheight=0 noruler laststatus=0")
+    feed(':call input("foo >")<cr>')
+    screen:expect{grid=[[
+                               |
+      ~                        |
+      ~                        |
+      ~                        |
+      foo >^                    |
+    ]]}
+    eq(1, eval('&cmdheight'))
+    feed('<cr>')
+    screen:expect{grid=[[
+      ^                         |
+      ~                        |
+      ~                        |
+      ~                        |
+      ~                        |
+    ]], showmode={}}
+    eq(0, eval('&cmdheight'))
+  end)
+
+  it("with winbar and splits", function()
+    command("set cmdheight=0 noruler laststatus=3 winbar=foo")
+    feed(':split<CR>')
+    screen:expect{grid=[[
+      foo                      |
+                               |
+      E36: Not enough room     |
+      Press ENTER or type comma|
+      nd to continue^           |
+    ]]}
+    feed('<CR>')
+    screen:expect{grid=[[
+      foo                      |
+      ^                         |
+      ~                        |
+      ~                        |
+      [No Name]                |
+    ]]}
+    feed(':')
+    screen:expect{grid=[[
+      foo                      |
+                               |
+      ~                        |
+      [No Name]                |
+      :^                        |
+    ]]}
+    feed('<Esc>')
+    screen:expect{grid=[[
+      foo                      |
+      ^                         |
+      ~                        |
+      ~                        |
+      [No Name]                |
+    ]], showmode={}}
+    eq(0, eval('&cmdheight'))
+
+    assert_alive()
+  end)
+end)
diff --git a/test/functional/ui/messages_spec.lua b/test/functional/ui/messages_spec.lua
index 7c789a9e58..e9c0e1b2a1 100644
--- a/test/functional/ui/messages_spec.lua
+++ b/test/functional/ui/messages_spec.lua
@@ -737,7 +737,6 @@ describe('ui/ext_messages', function()
     ]])
     eq(0, eval('&cmdheight'))
 
-    -- normally this would be an error
     feed(':set cmdheight=0')
     screen:expect{grid=[[
       ^                         |
diff --git a/test/functional/ui/statusline_spec.lua b/test/functional/ui/statusline_spec.lua
index 3e1b284856..2733b9dd4a 100644
--- a/test/functional/ui/statusline_spec.lua
+++ b/test/functional/ui/statusline_spec.lua
@@ -313,5 +313,9 @@ describe('global statusline', function()
     eq(2, meths.get_option('cmdheight'))
     meths.input_mouse('left', 'drag', '', 0, 14, 10)
     eq(1, meths.get_option('cmdheight'))
+    meths.input_mouse('left', 'drag', '', 0, 15, 10)
+    eq(0, meths.get_option('cmdheight'))
+    meths.input_mouse('left', 'drag', '', 0, 14, 10)
+    eq(1, meths.get_option('cmdheight'))
   end)
 end)