fix(messages): don't set cmdline_row when messages have scrolled (#21015

)

When 'cmdheight' is changed while messages have scrolled, the position
of msg_grid is not moved up, so cmdline_row should not be set based on
the position of msg_grid.

src/nvim/message.c

@@ -196,7 +196,7 @@ void msg_grid_validate(void)
  msg_grid_set_pos(max_rows, false);
  }
 
- if (msg_grid.chars && cmdline_row < msg_grid_pos) {
+ if (msg_grid.chars && !msg_scrolled && cmdline_row < msg_grid_pos) {
  // TODO(bfredl): this should already be the case, but fails in some
  // "batched" executions where compute_cmdrow() use stale positions or
  // something.

test/functional/ui/messages_spec.lua

@@ -1236,6 +1236,34 @@ vimComment xxx match /\s"[^\-:.%#=*].*$/ms=s+1,lc=1 excludenl contains=@vim
  bar^ |
  ]])
  end)
+
+ it('consecutive calls to win_move_statusline() work after multiline message #21014',function()
+ async_meths.exec([[
+ echo "\n"
+ call win_move_statusline(0, -4)
+ call win_move_statusline(0, 4)
+ ]], false)
+ screen:expect([[
+ |
+ {1:~ }|
+ {1:~ }|
+ {1:~ }|
+ {3: }|
+ |
+ {4:Press ENTER or type command to continue}^ |
+ ]])
+ feed('<CR>')
+ screen:expect([[
+ ^ |
+ {1:~ }|
+ {1:~ }|
+ {1:~ }|
+ {1:~ }|
+ {1:~ }|
+ |
+ ]])
+ eq(1, meths.get_option('cmdheight'))
+ end)
 end)
 
 it('calling screenstring() after redrawing between messages without UI #20999', function()