fix(extui): copy window config to new tabpage (#34308)

Problem:  When opening a new tabpage, extui windows are initialized with
          their default config. Window visiblity/dimensions on other
          tabpages may get out of sync with their buffer content.
Solution: Copy the config of the window to the new tabpage.
          No longer keep track of the various windows on each tabpage.
          Close windows on inactive tabpages instead (moving them could
          be more efficient but is currently not supported in the API).

runtime/lua/vim/_extui/messages.lua

@@ -54,8 +54,8 @@ function M.box:start_timer(buf, len)
       self.width = 1
       M.prev_msg = ext.cfg.msg.pos == 'box' and '' or M.prev_msg
       api.nvim_buf_clear_namespace(ext.bufs.box, -1, 0, -1)
-      if api.nvim_win_is_valid(ext.wins[ext.tab].box) then
-        api.nvim_win_set_config(ext.wins[ext.tab].box, { hide = true })
+      if api.nvim_win_is_valid(ext.wins.box) then
+        api.nvim_win_set_config(ext.wins.box, { hide = true })
       end
     end
   end, ext.cfg.msg.box.timeout)
@@ -85,10 +85,10 @@ local function set_virttext(type)
     M.cmd.last_col = type == 'last' and o.columns or M.cmd.last_col
   elseif #chunks > 0 then
     local tar = type == 'msg' and ext.cfg.msg.pos or 'cmd'
-    local win = ext.wins[ext.tab][tar]
+    local win = ext.wins[tar]
     local max = api.nvim_win_get_height(win)
     local erow = tar == 'cmd' and M.cmd.msg_row or nil
-    local srow = tar == 'box' and fn.line('w0', ext.wins[ext.tab].box) - 1 or nil
+    local srow = tar == 'box' and fn.line('w0', ext.wins.box) - 1 or nil
     local h = api.nvim_win_text_height(win, { start_row = srow, end_row = erow, max_height = max })
     local row = h.end_row ---@type integer
     local col = fn.virtcol2col(win, row + 1, h.end_vcol)
@@ -253,11 +253,11 @@ function M.show_msg(tar, content, replace_last, append, more)
   end
 
   if tar == 'box' then
-    api.nvim_win_set_width(ext.wins[ext.tab].box, width)
-    local h = api.nvim_win_text_height(ext.wins[ext.tab].box, { start_row = start_row })
+    api.nvim_win_set_width(ext.wins.box, width)
+    local h = api.nvim_win_text_height(ext.wins.box, { start_row = start_row })
     if more and h.all > 1 then
       msg_to_more(tar)
-      api.nvim_win_set_width(ext.wins[ext.tab].box, M.box.width)
+      api.nvim_win_set_width(ext.wins.box, M.box.width)
       return
     end
 
@@ -271,22 +271,22 @@ function M.show_msg(tar, content, replace_last, append, more)
       M.box:start_timer(ext.bufs.box, row - start_row + 1)
     end
   elseif tar == 'cmd' and dupe == 0 then
-    fn.clearmatches(ext.wins[ext.tab].cmd) -- Clear matchparen highlights.
+    fn.clearmatches(ext.wins.cmd) -- Clear matchparen highlights.
     if ext.cmd.row > 0 then
       -- In block mode the cmdheight is already dynamic, so just print the full message
       -- regardless of height. Spoof cmdline_show to put cmdline below message.
       ext.cmd.row = ext.cmd.row + 1 + row - start_row
       ext.cmd.cmdline_show({}, 0, ':', '', ext.cmd.indent, 0, 0)
-      api.nvim__redraw({ flush = true, cursor = true, win = ext.wins[ext.tab].cmd })
+      api.nvim__redraw({ flush = true, cursor = true, win = ext.wins.cmd })
     else
-      local h = api.nvim_win_text_height(ext.wins[ext.tab].cmd, {})
+      local h = api.nvim_win_text_height(ext.wins.cmd, {})
       if more and h.all > ext.cmdheight then
         ext.cmd.highlighter:destroy()
         msg_to_more(tar)
         return
       end
 
-      api.nvim_win_set_cursor(ext.wins[ext.tab][tar], { 1, 0 })
+      api.nvim_win_set_cursor(ext.wins[tar], { 1, 0 })
       ext.cmd.highlighter.active[ext.bufs.cmd] = nil
       -- Place [+x] indicator for lines that spill over 'cmdheight'.
       M.cmd.lines, M.cmd.msg_row = h.all, h.end_row
@@ -337,7 +337,7 @@ function M.msg_show(kind, content, _, _, append)
     -- Verbose messages are sent too often to be meaningful in the cmdline:
     -- always route to box regardless of cfg.msg.pos.
     M.show_msg('box', content, false, append)
-  elseif ext.cfg.msg.pos == 'cmd' and api.nvim_get_current_win() == ext.wins[ext.tab].more then
+  elseif ext.cfg.msg.pos == 'cmd' and api.nvim_get_current_win() == ext.wins.more then
     -- Append message to already open 'more' window.
     M.msg_history_show({ { 'spill', content } })
     api.nvim_command('norm! G')
@@ -411,7 +411,7 @@ function M.msg_history_show(entries)
   end
 
   -- Appending messages while 'more' window is open.
-  local append_more = api.nvim_get_current_win() == ext.wins[ext.tab].more
+  local append_more = api.nvim_get_current_win() == ext.wins.more
   if not append_more then
     api.nvim_buf_set_lines(ext.bufs.more, 0, -1, false, {})
   end
@@ -436,14 +436,14 @@ function M.set_pos(type)
       hide = false,
       relative = 'laststatus',
       height = height,
-      row = win == ext.wins[ext.tab].box and 0 or 1,
+      row = win == ext.wins.box and 0 or 1,
       col = 10000,
     }
     api.nvim_win_set_config(win, config)
     if type == 'box' then
       -- Ensure last line is visible and first line is at top of window.
       local row = (texth.all > height and texth.end_row or 0) + 1
-      api.nvim_win_set_cursor(ext.wins[ext.tab].box, { row, 0 })
+      api.nvim_win_set_cursor(ext.wins.box, { row, 0 })
     elseif type == 'more' and api.nvim_get_current_win() ~= win then
       -- Cannot leave the cmdwin to enter the "more" window, so close it.
       -- NOTE: regression w.r.t. the message grid, which allowed this. Resolving
@@ -473,7 +473,7 @@ function M.set_pos(type)
     end
   end
 
-  for t, win in pairs(ext.wins[ext.tab] or {}) do
+  for t, win in pairs(ext.wins) do
     local cfg = (t == type or (type == nil and t ~= 'cmd'))
       and api.nvim_win_is_valid(win)
       and api.nvim_win_get_config(win)