vim-patch:9.1.1831: stray vseps in right-most 'winfixwidth' window

Problem:  vertical separator of 'winfixwidth' windows may remain if they
          become right-most windows from closing windows to the right.
Solution: Don't implicitly rely on frame_new_width to fix vseps, as the
          call may be skipped for 'winfixwidth' windows to preserve
          their width; do it explicitly in winframe_remove (Sean Dewar).

Note that I prefer win_new_width here over setting w_width directly, which
would've previously been done by win_split_ins after frame_add_vsep, as this
wasn't true for winframe_remove.

Though the equivalent issue of bottom 'winfixheight' windows leaving stray
statuslines with &ls=0 doesn't seem to exist, test it anyway.

closes: vim/vim#18481

620c655677

Nvim: calling win_new_width over setting w_width directly is especially
important in making sure stuff like w_view_width is correct here.

Co-authored-by: Sean Dewar <6256228+seandewar@users.noreply.github.com>

src/nvim/window.c

@@ -1440,7 +1440,7 @@ win_T *win_split_ins(int size, int flags, win_T *new_wp, int dir, frame_T *to_fl
     }
     if (toplevel) {
       if (flags & WSP_BOT) {
-        frame_add_vsep(curfrp);
+        frame_set_vsep(curfrp, true);
       }
       // Set width of neighbor frame
       frame_new_width(curfrp, curfrp->fr_width
@@ -3230,6 +3230,12 @@ win_T *winframe_remove(win_T *win, int *dirp, tabpage_T *tp, frame_T **unflat_al
   int row = topleft->w_winrow;
   int col = topleft->w_wincol;
 
+  // If this is a rightmost window, remove vertical separators to the left.
+  if (win->w_vsep_width == 0 && frp_close->fr_parent->fr_layout == FR_ROW
+      && frp_close->fr_prev != NULL) {
+    frame_set_vsep(frp_close->fr_prev, false);
+  }
+
   // Remove this frame from the list of frames.
   frame_remove(frp_close);
 
@@ -3422,7 +3428,7 @@ void winframe_restore(win_T *wp, int dir, frame_T *unflat_altfr)
 
   // Vertical separators to the left may have been lost.  Restore them.
   if (wp->w_vsep_width == 0 && frp->fr_parent->fr_layout == FR_ROW && frp->fr_prev != NULL) {
-    frame_add_vsep(frp->fr_prev);
+    frame_set_vsep(frp->fr_prev, true);
   }
 
   // Statuslines or horizontal separators above may have been lost.  Restore them.
@@ -3868,23 +3874,26 @@ static void frame_new_width(frame_T *topfrp, int width, bool leftfirst, bool wfw
   topfrp->fr_width = width;
 }
 
-/// Add the vertical separator to windows at the right side of "frp".
+/// Add or remove the vertical separator of windows to the right side of "frp".
 /// Note: Does not check if there is room!
-static void frame_add_vsep(const frame_T *frp)
+static void frame_set_vsep(const frame_T *frp, bool add)
   FUNC_ATTR_NONNULL_ARG(1)
 {
   if (frp->fr_layout == FR_LEAF) {
     win_T *wp = frp->fr_win;
-    if (wp->w_vsep_width == 0) {
+    if (add && wp->w_vsep_width == 0) {
       if (wp->w_width > 0) {            // don't make it negative
-        wp->w_width--;
+        win_new_width(wp, wp->w_width - 1);
       }
       wp->w_vsep_width = 1;
+    } else if (!add && wp->w_vsep_width == 1) {
+      win_new_width(wp, wp->w_width + 1);
+      wp->w_vsep_width = 0;
     }
   } else if (frp->fr_layout == FR_COL) {
     // Handle all the frames in the column.
     FOR_ALL_FRAMES(frp, frp->fr_child) {
-      frame_add_vsep(frp);
+      frame_set_vsep(frp, add);
     }
   } else {
     assert(frp->fr_layout == FR_ROW);
@@ -3893,7 +3902,7 @@ static void frame_add_vsep(const frame_T *frp)
     while (frp->fr_next != NULL) {
       frp = frp->fr_next;
     }
-    frame_add_vsep(frp);
+    frame_set_vsep(frp, add);
   }
 }
 

test/functional/legacy/window_cmd_spec.lua

@@ -1,11 +1,14 @@
+local t = require('test.testutil')
 local n = require('test.functional.testnvim')()
 local Screen = require('test.functional.ui.screen')
 
 local clear = n.clear
+local eq = t.eq
 local exec = n.exec
 local exec_lua = n.exec_lua
 local command = n.command
 local feed = n.feed
+local fn = n.fn
 
 -- oldtest: Test_window_cmd_ls0_split_scrolling()
 it('scrolling with laststatus=0 and :botright split', function()
@@ -354,3 +357,53 @@ describe('splitkeep', function()
     ]])
   end)
 end)
+
+-- oldtest: Test_winfixsize_vsep_statusline()
+it("'winfixwidth/height' does not leave stray vseps/statuslines", function()
+  clear()
+  local screen = Screen.new(75, 8)
+  exec([[
+    set noequalalways splitbelow splitright
+    vsplit
+    setlocal winfixwidth
+    vsplit
+  ]])
+  eq(16, fn.winwidth(1))
+  eq(37, fn.winwidth(2))
+  eq(20, fn.winwidth(3))
+
+  command('quit')
+  screen:expect([[
+    ^                                    │                                      |
+    {1:~                                   }│{1:~                                     }|*5
+    {3:[No Name]                            }{2:[No Name]                             }|
+                                                                               |
+  ]])
+  -- Checks w_view_width in Nvim; especially important as the screen test may still pass if only
+  -- w_width changed to make room for the vsep.
+  eq(36, fn.winwidth(1))
+  eq(38, fn.winwidth(2))
+
+  exec([[
+    set laststatus=0
+    only
+    split
+    set winfixheight
+    split
+  ]])
+  eq(1, fn.winheight(1))
+  eq(3, fn.winheight(2))
+  eq(1, fn.winheight(3))
+
+  command('quit')
+  screen:expect([[
+    ^                                                                           |
+    {1:~                                                                          }|
+    {3:[No Name]                                                                  }|
+                                                                               |
+    {1:~                                                                          }|*3
+                                                                               |
+  ]])
+  eq(2, fn.winheight(1))
+  eq(4, fn.winheight(2))
+end)

test/old/testdir/test_window_cmd.vim

@@ -2261,4 +2261,50 @@ func Test_winfixsize_positions()
   %bwipe
 endfunc
 
+func Test_winfixsize_vsep_statusline()
+  CheckScreendump
+  let lines =<< trim END
+    set noequalalways splitbelow splitright
+    vsplit
+    setlocal winfixwidth
+    vsplit
+    func SetupWfh()
+      set laststatus=0
+      only
+      split
+      set winfixheight
+      split
+    endfunc
+  END
+  call writefile(lines, 'XTestWinfixsizeVsepStatusline', 'D')
+  let buf = RunVimInTerminal('-S XTestWinfixsizeVsepStatusline', #{rows: 8})
+
+  call term_sendkeys(buf, ":echo winwidth(1) winwidth(2) winwidth(3)\n")
+  call WaitForAssert({-> assert_match('^16 37 20\>', term_getline(buf, 8))})
+
+  call term_sendkeys(buf, ":quit\n")
+  call VerifyScreenDump(buf, 'Test_winfixsize_vsep_statusline_1', {})
+
+  " Reported widths should be consistent with the screen dump.
+  call term_sendkeys(buf, ":echo winwidth(1) winwidth(2)\n")
+  " (May be better if 'wfw' window remains at 37 columns, but the resize is
+  " consistent with how things currently work for 'winfix*' windows)
+  call WaitForAssert({-> assert_match('^36 38\>', term_getline(buf, 8))})
+
+  " For good measure, also check bottom-most 'winfixheight' windows don't leave
+  " stray statuslines with &laststatus=0.
+  call term_sendkeys(buf,
+        \ ":call SetupWfh() | echo winheight(1) winheight(2) winheight(3)\n")
+  call WaitForAssert({-> assert_match('^1 3 1\>', term_getline(buf, 8))})
+
+  call term_sendkeys(buf, ":quit\n")
+  call VerifyScreenDump(buf, 'Test_winfixsize_vsep_statusline_2', {})
+
+  call term_sendkeys(buf, ":echo winheight(1) winheight(2)\n")
+  " (Likewise, may be better if 'wfh' window remains at 3 rows)
+  call WaitForAssert({-> assert_match('^2 4\>', term_getline(buf, 8))})
+
+  call StopVimInTerminal(buf)
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab