perf(extui): delay creating windows, buffers and parser (#34665)

Problem:  vim._extui unconditionally creates windows, buffers and the
          Vimscript cmdline highlighter when it is first loaded.
Solution: Schedule first creation of the window so that first redraw
          happens sooner (still need to create at least the cmdline
          window asap as it can have a different highlight through
          hl-MsgArea; thus further delaying until the first event that
          needs a particular target seems redundant). Load the cmdline
          highlighter on the first cmdline_show event.

1 files changed, 5 insertions, 13 deletions

diff --git a/runtime/lua/vim/_extui/shared.lua b/runtime/lua/vim/_extui/shared.lua
index 0045748039..9454653c58 100644
--- a/runtime/lua/vim/_extui/shared.lua
+++ b/runtime/lua/vim/_extui/shared.lua
@@ -1,10 +1,10 @@
-local api, o = vim.api, vim.o
+local api = vim.api
 local M = {
   msg = nil, ---@type vim._extui.messages
   cmd = nil, ---@type vim._extui.cmdline
   ns = api.nvim_create_namespace('nvim._ext_ui'),
   augroup = api.nvim_create_augroup('nvim._ext_ui', {}),
-  cmdheight = -1, -- 'cmdheight' option value set by user.
+  cmdheight = 1, -- 'cmdheight' option value set by user.
   wins = { cmd = -1, dialog = -1, msg = -1, pager = -1 },
   bufs = { cmd = -1, dialog = -1, msg = -1, pager = -1 },
   cfg = {
@@ -28,18 +28,13 @@ local wincfg = { -- Default cfg for nvim_open_win().
 }
 
 local tab = 0
---- Ensure the various buffers and windows have not been deleted.
-function M.tab_check_wins()
+---Ensure target buffers and windows are still valid.
+function M.check_targets()
   local curtab = api.nvim_get_current_tabpage()
   for _, type in ipairs({ 'cmd', 'dialog', 'msg', 'pager' }) do
     local setopt = not api.nvim_buf_is_valid(M.bufs[type])
     if setopt then
       M.bufs[type] = api.nvim_create_buf(false, true)
-      if type == 'cmd' then
-        -- Attach highlighter to the cmdline buffer.
-        local parser = assert(vim.treesitter.get_parser(M.bufs.cmd, 'vim', {}))
-        M.cmd.highlighter = vim.treesitter.highlighter.new(parser)
-      end
     end
 
     if
@@ -47,15 +42,12 @@ function M.tab_check_wins()
       or not api.nvim_win_is_valid(M.wins[type])
       or not api.nvim_win_get_config(M.wins[type]).zindex -- no longer floating
     then
-      local top = { vim.opt.fcs:get().horiz or o.ambw == 'single' and '─' or '-', 'WinSeparator' }
-      local border = (type == 'pager' or type == 'dialog') and { '', top, '', '', '', '', '', '' }
       local cfg = vim.tbl_deep_extend('force', wincfg, {
         focusable = type == 'pager',
         mouse = type ~= 'cmd' and true or nil,
         anchor = type ~= 'cmd' and 'SE' or nil,
         hide = type ~= 'cmd' or M.cmdheight == 0 or nil,
-        title = type == 'pager' and 'Pager' or nil,
-        border = type == 'msg' and 'single' or border or 'none',
+        border = type == 'msg' and 'single' or 'none',
         -- kZIndexMessages < zindex < kZIndexCmdlinePopupMenu (grid_defs.h), pager below others.
         zindex = 200 - (type == 'pager' and 1 or 0),
         _cmdline_offset = type == 'cmd' and 0 or nil,