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

diff --git a/src/xdg.c b/src/xdg.c
index 9be6338b104a540e2b1ce5333caf44bc68be914f..5cddf44a7791eda46d5910637a6a9370dcaabda4 100644 (file)
--- 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 b00119c66278239b28f5159ef2044949862e67f6..ae4053112e58f4e54ea2972d005fd818bb10c3f3 100644 (file)
--- 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;
        }