desktop-shell: detect stale shell surface outputs

When displays are hot (un)plugged, it may happen that
a shell surface is left with a stale pointer to an output
that has already been freed. Add an output destroy listener
to catch such situations and set the output pointer to NULL.

Signed-off-by: Semi Malinen <semi.malinen@ge.com>
Signed-off-by: Fabien Lahoudere <fabien.lahoudere@collabora.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>

diff --git a/desktop-shell/shell.c b/desktop-shell/shell.c
index 1e153cb..64db89f 100644 (file)
--- a/desktop-shell/shell.c
+++ b/desktop-shell/shell.c
@@ -128,6 +128,7 @@ struct shell_surface {
 
        struct weston_output *fullscreen_output;
        struct weston_output *output;
+       struct wl_listener output_destroy_listener;
 
        struct surface_state {
                bool fullscreen;
@@ -1934,6 +1935,17 @@ shell_surface_update_layer(struct shell_surface *shsurf)
 }
 
 static void
+notify_output_destroy(struct wl_listener *listener, void *data)
+{
+       struct shell_surface *shsurf =
+               container_of(listener,
+                            struct shell_surface, output_destroy_listener);
+
+       shsurf->output = NULL;
+       shsurf->output_destroy_listener.notify = NULL;
+}
+
+static void
 shell_surface_set_output(struct shell_surface *shsurf,
                          struct weston_output *output)
 {
@@ -1948,6 +1960,18 @@ shell_surface_set_output(struct shell_surface *shsurf,
                shsurf->output = es->output;
        else
                shsurf->output = get_default_output(es->compositor);
+
+       if (shsurf->output_destroy_listener.notify) {
+               wl_list_remove(&shsurf->output_destroy_listener.link);
+               shsurf->output_destroy_listener.notify = NULL;
+       }
+
+       if (!shsurf->output)
+               return;
+
+       shsurf->output_destroy_listener.notify = notify_output_destroy;
+       wl_signal_add(&shsurf->output->destroy_signal,
+                     &shsurf->output_destroy_listener);
 }
 
 static void
@@ -1986,7 +2010,7 @@ unset_maximized(struct shell_surface *shsurf)
                weston_desktop_surface_get_surface(shsurf->desktop_surface);
 
        /* undo all maximized things here */
-       shsurf->output = get_default_output(surface->compositor);
+       shell_surface_set_output(shsurf, get_default_output(surface->compositor));
 
        if (shsurf->saved_position_valid)
                weston_view_set_position(shsurf->view,
@@ -2348,7 +2372,8 @@ desktop_surface_added(struct weston_desktop_surface *desktop_surface,
        shsurf->fullscreen.black_view = NULL;
        wl_list_init(&shsurf->fullscreen.transform.link);
 
-       shsurf->output = get_default_output(shsurf->shell->compositor);
+       shell_surface_set_output(
+               shsurf, get_default_output(shsurf->shell->compositor));
 
        wl_signal_init(&shsurf->destroy_signal);