vim-patch:9.1.0116: win_split_ins may not check available room

Problem:  win_split_ins has no check for E36 when moving an existing
          window
Solution: check for room and fix the issues in f_win_splitmove()
          (Sean Dewar)

https://github.com/vim/vim/commit/0fd44a5ad81ade342cb54d8984965bdedd2272c8

Omit WSP_FORCE_ROOM, as it's not needed for Nvim's autocmd window, which is
floating. Shouldn't be difficult to port later if it's used for anything else.

Make win_splitmove continue working for turning floating windows into splits.
Move the logic for "unfloating" a float to win_split_ins; unlike splits, no
changes to the window layout are needed before calling it, as floats take no
room in the window layout and cannot affect the e_noroom check.

Add missing tp_curwin-fixing logic for turning external windows into splits, and
add a test.
NOTE: there are other issues with the way "tabpage independence" is implemented
for external windows; namely, some things assume that tp_curwin is indeed a
window within that tabpage, and as such, functions like tabpage_winnr and
nvim_tabpage_get_win currently don't always work for external windows (with the
latter aborting!)

Use last_status over frame_add_statusline, as Nvim's last_status already does
this for all windows in the current tabpage. Adjust restore_full_snapshot_rec to
handle this.
This "restore everything" approach is changed in a future commit anyway, so only
ensure it's robust enough to just pass tests.

Keep check_split_disallowed's current doc comment, as it's actually a bit more
accurate here. (I should probably PR Vim to use this one)

Allow f_win_splitmove to move a floating "wp" into a split; Nvim supports this.
Continue to disallow it from moving the autocommand window into a split (funnily
enough, the check wasn't reachable before, as moving a float was disallowed),
but now return -1 in that case (win_splitmove also returns FAIL for this, but
handling it in f_win_splitmove avoids us needing to switch windows first).

Cherry-pick Test_window_split_no_room fix from v9.1.0121.

Update nvim_win_set_config to handle win_split_ins failure in later commits.

1 files changed, 25 insertions, 41 deletions

diff --git a/src/nvim/eval/window.c b/src/nvim/eval/window.c
index b8aa0c9641..17b8b01963 100644
--- a/src/nvim/eval/window.c
+++ b/src/nvim/eval/window.c
@@ -659,55 +659,19 @@ void f_win_screenpos(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   tv_list_append_number(rettv->vval.v_list, wp == NULL ? 0 : wp->w_wincol + 1);
 }
 
-/// Move the window wp into a new split of targetwin in a given direction
-static void win_move_into_split(win_T *wp, win_T *targetwin, int size, int flags)
-{
-  int height = wp->w_height;
-  win_T *oldwin = curwin;
-
-  if (wp == targetwin || is_aucmd_win(wp)) {
-    return;
-  }
-
-  // Jump to the target window
-  if (curwin != targetwin) {
-    win_goto(targetwin);
-  }
-
-  // Remove the old window and frame from the tree of frames
-  int dir;
-  winframe_remove(wp, &dir, NULL);
-  win_remove(wp, NULL);
-  last_status(false);     // may need to remove last status line
-  win_comp_pos();   // recompute window positions
-
-  // Split a window on the desired side and put the old window there
-  win_split_ins(size, flags, wp, dir);
-
-  // If splitting horizontally, try to preserve height
-  if (size == 0 && !(flags & WSP_VERT)) {
-    win_setheight_win(height, wp);
-    if (p_ea) {
-      win_equal(wp, true, 'v');
-    }
-  }
-
-  if (oldwin != curwin) {
-    win_goto(oldwin);
-  }
-}
-
 /// "win_splitmove()" function
 void f_win_splitmove(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 {
   win_T *wp = find_win_by_nr_or_id(&argvars[0]);
   win_T *targetwin = find_win_by_nr_or_id(&argvars[1]);
+  win_T *oldwin = curwin;
+
+  rettv->vval.v_number = -1;
 
   if (wp == NULL || targetwin == NULL || wp == targetwin
       || !win_valid(wp) || !win_valid(targetwin)
-      || win_float_valid(wp) || win_float_valid(targetwin)) {
+      || targetwin->w_floating) {
     emsg(_(e_invalwindow));
-    rettv->vval.v_number = -1;
     return;
   }
 
@@ -732,7 +696,27 @@ void f_win_splitmove(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
     size = (int)tv_dict_get_number(d, "size");
   }
 
-  win_move_into_split(wp, targetwin, size, flags);
+  // Check if we can split the target before we bother switching windows.
+  if (is_aucmd_win(wp) || check_split_disallowed(targetwin) == FAIL) {
+    return;
+  }
+
+  if (curwin != targetwin) {
+    win_goto(targetwin);
+  }
+
+  // Autocommands may have sent us elsewhere or closed "wp" or "oldwin".
+  if (curwin == targetwin && win_valid(wp)) {
+    if (win_splitmove(wp, size, flags) == OK) {
+      rettv->vval.v_number = 0;
+    }
+  } else {
+    emsg(_(e_auabort));
+  }
+
+  if (oldwin != curwin && win_valid(oldwin)) {
+    win_goto(oldwin);
+  }
 }
 
 /// "win_gettype(nr)" function