vim-patch:partial:9.0.0907: restoring window after WinScrolled may fail

Problem:    Restoring window after WinScrolled may fail.
Solution:   Lock the window layout when triggering WinScrolled.

d63a85592c

Only check close_disallowed in window_layout_locked() for now.
Also don't check window_layout_locked() when closing a floating window,
as it's not checked when creating a floating window.

Co-authored-by: Bram Moolenaar <Bram@vim.org>

src/nvim/errors.h

@@ -195,6 +195,8 @@ EXTERN const char e_stray_closing_curly_str[]
 INIT(= N_("E1278: Stray '}' without a matching '{': %s"));
 EXTERN const char e_missing_close_curly_str[]
 INIT(= N_("E1279: Missing '}': %s"));
+EXTERN const char e_not_allowed_to_change_window_layout_in_this_autocmd[]
+INIT(= N_("E1312: Not allowed to change the window layout in this autocmd"));
 
 EXTERN const char e_val_too_large[] INIT(= N_("E1510: Value too large: %s"));
 

src/nvim/ex_docmd.c

@@ -5033,6 +5033,9 @@ void ex_win_close(int forceit, win_T *win, tabpage_T *tp)
     emsg(_(e_autocmd_close));
     return;
   }
+  if (!win->w_floating && window_layout_locked()) {
+    return;
+  }
 
   buf_T *buf = win->w_buffer;
 
@@ -5074,6 +5077,10 @@ static void ex_tabclose(exarg_T *eap)
     return;
   }
 
+  if (window_layout_locked()) {
+    return;
+  }
+
   int tab_number = get_tabpage_arg(eap);
   if (eap->errmsg != NULL) {
     return;
@@ -5105,6 +5112,10 @@ static void ex_tabonly(exarg_T *eap)
     return;
   }
 
+  if (window_layout_locked()) {
+    return;
+  }
+
   int tab_number = get_tabpage_arg(eap);
   if (eap->errmsg != NULL) {
     return;
@@ -5175,9 +5186,12 @@ void tabpage_close_other(tabpage_T *tp, int forceit)
 /// ":only".
 static void ex_only(exarg_T *eap)
 {
-  win_T *wp;
+  if (window_layout_locked()) {
+    return;
+  }
 
   if (eap->addr_count > 0) {
+    win_T *wp;
     linenr_T wnr = eap->line2;
     for (wp = firstwin; --wnr > 0;) {
       if (wp->w_next == NULL) {
@@ -5185,11 +5199,9 @@ static void ex_only(exarg_T *eap)
       }
       wp = wp->w_next;
     }
-  } else {
-    wp = curwin;
-  }
-  if (wp != curwin) {
-    win_goto(wp);
+    if (wp != curwin) {
+      win_goto(wp);
+    }
   }
   close_others(true, eap->forceit);
 }
@@ -5201,11 +5213,11 @@ static void ex_hide(exarg_T *eap)
     return;
   }
 
+  win_T *win = NULL;
   if (eap->addr_count == 0) {
-    win_close(curwin, false, eap->forceit);  // don't free buffer
+    win = curwin;
   } else {
     int winnr = 0;
-    win_T *win = NULL;
 
     FOR_ALL_WINDOWS_IN_TAB(wp, curtab) {
       winnr++;
@@ -5217,8 +5229,13 @@ static void ex_hide(exarg_T *eap)
     if (win == NULL) {
       win = lastwin;
     }
-    win_close(win, false, eap->forceit);
   }
+
+  if (!win->w_floating && window_layout_locked()) {
+    return;
+  }
+
+  win_close(win, false, eap->forceit);  // don't free buffer
 }
 
 /// ":stop" and ":suspend": Suspend Vim.

src/nvim/window.c

@@ -108,6 +108,38 @@ static char *m_onlyone = N_("Already only one window");
 /// autocommands mess up the window structure.
 static int split_disallowed = 0;
 
+/// When non-zero closing a window is forbidden.  Used to avoid that nasty
+/// autocommands mess up the window structure.
+static int close_disallowed = 0;
+
+/// Disallow changing the window layout (split window, close window, move
+/// window).  Resizing is still allowed.
+/// Used for autocommands that temporarily use another window and need to
+/// make sure the previously selected window is still there.
+/// Must be matched with exactly one call to window_layout_unlock()!
+static void window_layout_lock(void)
+{
+  split_disallowed++;
+  close_disallowed++;
+}
+
+static void window_layout_unlock(void)
+{
+  split_disallowed--;
+  close_disallowed--;
+}
+
+/// When the window layout cannot be changed give an error and return true.
+bool window_layout_locked(void)
+{
+  // if (split_disallowed > 0 || close_disallowed > 0) {
+  if (close_disallowed > 0) {
+    emsg(_(e_not_allowed_to_change_window_layout_in_this_autocmd));
+    return true;
+  }
+  return false;
+}
+
 // #define WIN_DEBUG
 #ifdef WIN_DEBUG
 /// Call this method to log the current window layout.
@@ -2739,6 +2771,9 @@ int win_close(win_T *win, bool free_buf, bool force)
     emsg(_(e_cannot_close_last_window));
     return FAIL;
   }
+  if (!win->w_floating && window_layout_locked()) {
+    return FAIL;
+  }
 
   if (win_locked(win)
       || (win->w_buffer != NULL && win->w_buffer->b_locked > 0)) {
@@ -4315,6 +4350,9 @@ int win_new_tabpage(int after, char *filename)
     emsg(_(e_cmdwin));
     return FAIL;
   }
+  if (window_layout_locked()) {
+    return FAIL;
+  }
 
   tabpage_T *newtp = alloc_tabpage();