From e5d459aa0cf4b173cd37ecc7267591f544c42800 Mon Sep 17 00:00:00 2001
From: Consolatis <35009135+Consolatis@users.noreply.github.com>
Date: Thu, 21 Sep 2023 18:13:44 +0200
Subject: [PATCH] Ensure xdg and xwayland string_prop() handlers deal with
 destroying views

When a view is destroyed (including override_redirect in the xwayland
case), the view_destroy() handler is called which checks for a currently
open A-Tab window switcher and causes an update there to remove the
destroying view from the list. Before view_destroy() is called, both
xwayland and xdg handlers reset the xdg_surface / xwayland_surface.

The window switcher update then creates a list of all windows which do
not have the 'skipWindowSwitcher' window rule property set. If there is
at least one 'matchOnce' window rule configured, this also tries to get
string properties of the destroying view which already had their
xdg_surface / xwayland_surface reset and thus run into an assert.

This patch fixes that so that the string_prop() handlers always return
an empty string in those cases rather than running into the assert.

For a more in-depth analyses and alternative solutions see the linked
issue.

Fixes #1082
---
 src/xdg.c      | 14 +++++++++++++-
 src/xwayland.c | 13 +++++++++++--
 2 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/src/xdg.c b/src/xdg.c
index 9be6338b..5cddf44a 100644
--- a/src/xdg.c
+++ b/src/xdg.c
@@ -439,7 +439,19 @@ position_xdg_toplevel_view(struct view *view)
 static const char *
 xdg_toplevel_view_get_string_prop(struct view *view, const char *prop)
 {
-	struct wlr_xdg_toplevel *xdg_toplevel = xdg_toplevel_from_view(view);
+	struct xdg_toplevel_view *xdg_view = xdg_toplevel_view_from_view(view);
+	struct wlr_xdg_toplevel *xdg_toplevel = xdg_view->xdg_surface
+		? xdg_view->xdg_surface->toplevel
+		: NULL;
+	if (!xdg_toplevel) {
+		/*
+		 * This may happen due to a matchOnce rule when
+		 * a view is destroyed while A-Tab is open. See
+		 * https://github.com/labwc/labwc/issues/1082#issuecomment-1716137180
+		 */
+		return "";
+	}
+
 	if (!strcmp(prop, "title")) {
 		return xdg_toplevel->title;
 	}
diff --git a/src/xwayland.c b/src/xwayland.c
index b00119c6..ae405311 100644
--- a/src/xwayland.c
+++ b/src/xwayland.c
@@ -355,8 +355,17 @@ xwayland_view_close(struct view *view)
 static const char *
 xwayland_view_get_string_prop(struct view *view, const char *prop)
 {
-	struct wlr_xwayland_surface *xwayland_surface =
-		xwayland_surface_from_view(view);
+	struct xwayland_view *xwayland_view = xwayland_view_from_view(view);
+	struct wlr_xwayland_surface *xwayland_surface = xwayland_view->xwayland_surface;
+	if (!xwayland_surface) {
+		/*
+		 * This may happen due to a matchOnce rule when
+		 * a view is destroyed while A-Tab is open. See
+		 * https://github.com/labwc/labwc/issues/1082#issuecomment-1716137180
+		 */
+		return "";
+	}
+
 	if (!strcmp(prop, "title")) {
 		return xwayland_surface->title;
 	}