fix(ui): startup intro message should be visible with ext_multigrid

As this message is literally drawn on top of the EOB area of the first
window, the simple solution is to just draw the message on top of the
grid of the first window.

We still want #24764 (msg_intro event) but now only for ext_messages.

1 files changed, 76 insertions, 0 deletions

diff --git a/test/functional/ui/messages_spec.lua b/test/functional/ui/messages_spec.lua
index 131622bcc5..92a925ad31 100644
--- a/test/functional/ui/messages_spec.lua
+++ b/test/functional/ui/messages_spec.lua
@@ -1751,6 +1751,82 @@ describe('ui/ext_messages', function()
   end)
 end)
 
+it('ui/ext_multigrid supports intro screen', function()
+  clear { args_rm = { '--headless' }, args = { '--cmd', 'set shortmess-=I' } }
+  local screen = Screen.new(80, 24)
+  screen:attach({ rgb = true, ext_multigrid = true })
+  screen:set_default_attr_ids {
+    [1] = { bold = true, foreground = Screen.colors.Blue1 },
+    [2] = { foreground = Screen.colors.Grey100, background = Screen.colors.Red },
+    [3] = { bold = true },
+    [4] = { bold = true, foreground = Screen.colors.SeaGreen4 },
+    [5] = { foreground = Screen.colors.Blue1 },
+  }
+
+  screen:expect {
+    grid = [[
+    ## grid 1
+      [2:--------------------------------------------------------------------------------]|*23
+      [3:--------------------------------------------------------------------------------]|
+    ## grid 2
+      ^                                                                                |
+      {1:~                                                                               }|*4
+      {MATCH:.*}|
+      {1:~                                                                               }|
+      {1:~                 }Nvim is open source and freely distributable{1:                  }|
+      {1:~                           }https://neovim.io/#chat{1:                             }|
+      {1:~                                                                               }|
+      {1:~                }type  :help nvim{5:<Enter>}       if you are new! {1:                 }|
+      {1:~                }type  :checkhealth{5:<Enter>}     to optimize Nvim{1:                 }|
+      {1:~                }type  :q{5:<Enter>}               to exit         {1:                 }|
+      {1:~                }type  :help{5:<Enter>}            for help        {1:                 }|
+      {1:~                                                                               }|
+      {1:~{MATCH: +}}type  :help news{5:<Enter>} to see changes in v{MATCH:%d+%.%d+}{1:{MATCH: +}}|
+      {1:~                                                                               }|
+      {MATCH:.*}|*2
+      {1:~                                                                               }|*4
+    ## grid 3
+                                                                                      |
+    ]],
+    win_viewport = {
+      [2] = {
+        win = 1000,
+        topline = 0,
+        botline = 2,
+        curline = 0,
+        curcol = 0,
+        linecount = 1,
+        sum_scroll_delta = 0,
+      },
+    },
+  }
+
+  feed 'ix'
+  screen:expect {
+    grid = [[
+    ## grid 1
+      [2:--------------------------------------------------------------------------------]|*23
+      [3:--------------------------------------------------------------------------------]|
+    ## grid 2
+      x^                                                                               |
+      {1:~                                                                               }|*22
+    ## grid 3
+      {3:-- INSERT --}                                                                    |
+    ]],
+    win_viewport = {
+      [2] = {
+        win = 1000,
+        topline = 0,
+        botline = 2,
+        curline = 0,
+        curcol = 1,
+        linecount = 1,
+        sum_scroll_delta = 0,
+      },
+    },
+  }
+end)
+
 describe('ui/msg_puts_printf', function()
   it('output multibyte characters correctly', function()
     local screen