fix(window): prevent win_size_restore from changing cmdheight

Currently it only skips if `Rows` changed, but it's possible for the height of
the usable area for windows to change (e.g: via `&ch`, `&stal` or `&ls`), which
can cause the value of `&cmdheight` to change when the sizes are restored.

This is a Vim bug, so I've submitted a PR there too. No telling when it'll be
merged though, given the current lack of activity there.

`ROWS_AVAIL` is convenient here, but also subtracts the `global_stl_height()`.
Not ideal, as we also care about the height of the last statusline for other
values of `&ls`. Meh.

Introduce `last_stl_height` for getting the height of the last statusline and
use it in `win_size_save/restore` and `last_status` (means
`last_status_rec`'s `statusline` argument will now be true if `&ls` is 3,
but that does not change the behaviour).

Also corrects the logic in `comp_col` to not assume there's a last statusline
if `&ls` is 1 and the last window is floating.

1 files changed, 33 insertions, 1 deletions

diff --git a/test/functional/ui/cmdline_spec.lua b/test/functional/ui/cmdline_spec.lua
index dc29b765bd..a8cc8e00f0 100644
--- a/test/functional/ui/cmdline_spec.lua
+++ b/test/functional/ui/cmdline_spec.lua
@@ -984,14 +984,46 @@ it('tabline is not redrawn in Ex mode #24122', function()
 end)
 
 describe("cmdline height", function()
+  before_each(clear)
+
   it("does not crash resized screen #14263", function()
-    clear()
     local screen = Screen.new(25, 10)
     screen:attach()
     command('set cmdheight=9999')
     screen:try_resize(25, 5)
     assert_alive()
   end)
+
+  it('unchanged when trying to restore window sizes', function()
+    command('set showtabline=0 cmdheight=2 laststatus=0')
+    feed('q:')  -- Closing cmdwin tries to restore sizes
+    command('set cmdheight=1 | quit')
+    eq(1, eval('&cmdheight'))
+
+    command('set showtabline=2 cmdheight=3')
+    feed('q:')
+    command('set showtabline=0 | quit')
+    eq(3, eval('&cmdheight'))
+
+    command('set cmdheight=1 laststatus=2')
+    feed('q:')
+    command('set laststatus=0 | quit')
+    eq(1, eval('&cmdheight'))
+
+    command('set laststatus=2')
+    feed('q:')
+    command('set laststatus=1 | quit')
+    eq(1, eval('&cmdheight'))
+
+    command('set laststatus=2 | belowright vsplit | wincmd _')
+    local restcmds = eval('winrestcmd()')
+    feed('q:')
+    command('set laststatus=1 | quit')
+    -- As we have 2 windows, &ls = 1 should still have a statusline on the last
+    -- window. As such, the number of available rows hasn't changed and the window
+    -- sizes should be restored.
+    eq(restcmds, eval('winrestcmd()'))
+  end)
 end)
 
 describe('cmdheight=0', function()