vim-patch:9.1.0175: wrong window positions with 'winfix{width,height}' (#27845)

Problem:  winframe functions incorrectly recompute window positions if
          the altframe wasn't adjacent to the closed frame, which is
          possible if adjacent windows had 'winfix{width,height}' set.

Solution: recompute for windows within the parent of the altframe and
          closed frame. Skip this (as before) if the altframe was
          top/left, but only if adjacent to the closed frame, as
          positions won't change in that case. Also correct the return
          value documentation for win_screenpos. (Sean Dewar)

The issue revealed itself after removing the win_comp_pos call below
winframe_restore in win_splitmove. Similarly, wrong positions could result from
windows closed in other tabpages, as win_free_mem uses winframe_remove (at least
until it is entered later, where enter_tabpage calls win_comp_pos).

NOTE: As win_comp_pos handles only curtab, it's possible via other means for
positions in non-current tabpages to be wrong (e.g: after changing 'laststatus',
'showtabline', etc.). Given enter_tabpage recomputes it, maybe it's intentional
as an optimization? Should probably be documented in win_screenpos then, but I
won't address that here.

closes: vim/vim#14191

Nvim: don't reuse "wp" for "topleft" in winframe_remove, so the change
integrates better with the call to winframe_find_altwin before it.

5866bc3a0f

test/old/testdir/test_window_cmd.vim

@@ -200,11 +200,11 @@ func Test_window_split_edit_bufnr()
   %bw!
 endfunc
 
-func s:win_layout_info() abort
+func s:win_layout_info(tp = tabpagenr()) abort
   return #{
-        \ layout: winlayout(),
-        \ pos_sizes: range(1, winnr('$'))
-        \            ->map({_, nr -> win_getid(nr)->getwininfo()[0]})
+        \ layout: winlayout(a:tp),
+        \ pos_sizes: range(1, tabpagewinnr(a:tp, '$'))
+        \            ->map({_, nr -> win_getid(nr, a:tp)->getwininfo()[0]})
         \            ->map({_, wininfo -> #{id: wininfo.winid,
         \                                   row: wininfo.winrow,
         \                                   col: wininfo.wincol,
@@ -2145,4 +2145,69 @@ func Test_win_gotoid_splitmove_textlock_cmdwin()
            \ .. ":call assert_equal('', win_gettype(winnr('#')))\<CR>", 'ntx')
 endfunc
 
+func Test_winfixsize_positions()
+  " Check positions are correct when closing a window in a non-current tabpage
+  " causes non-adjacent window to fill the space due to 'winfix{width,height}'.
+  tabnew
+  vsplit
+  wincmd |
+  split
+  set winfixheight
+  split foo
+  tabfirst
+
+  bwipe! foo
+  " Save actual values before entering the tabpage.
+  let info = s:win_layout_info(2)
+  tabnext
+  " Compare it with the expected value (after win_comp_pos) from entering.
+  call assert_equal(s:win_layout_info(), info)
+
+  $tabnew
+  split
+  split
+  wincmd k
+  belowright vsplit
+  set winfixwidth
+  belowright vsplit foo
+  tabprevious
+
+  bwipe! foo
+  " Save actual values before entering the tabpage.
+  let info = s:win_layout_info(3)
+  tabnext
+  " Compare it with the expected value (after win_comp_pos) from entering.
+  call assert_equal(s:win_layout_info(), info)
+
+  " Check positions unchanged when failing to move a window, if 'winfix{width,
+  " height}' would otherwise cause a non-adjacent window to fill the space.
+  %bwipe
+  call assert_fails('execute "split|"->repeat(&lines)', 'E36:')
+  wincmd p
+  vsplit
+  set winfixwidth
+  vsplit
+  set winfixwidth
+  vsplit
+  vsplit
+  set winfixwidth
+  wincmd p
+
+  let info = s:win_layout_info()
+  call assert_fails('wincmd J', 'E36:')
+  call assert_equal(info, s:win_layout_info())
+
+  only
+  call assert_fails('execute "vsplit|"->repeat(&columns)', 'E36:')
+  belowright split
+  set winfixheight
+  belowright split
+
+  let info = s:win_layout_info()
+  call assert_fails('wincmd H', 'E36:')
+  call assert_equal(info, s:win_layout_info())
+
+  %bwipe
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab