gtk::gsk::Renderer raise g_object_unref: assertion 'G_IS_OBJECT (object)' failed

[plrigaux]

Hello I found the following issue.

Bug description

I made this function based on Adwaita Demo debug info code

fn get_gtk_info() -> (String, String) {
    let mut backend = String::new();
    let mut renderer = String::new();

    if let Some(display) = gdk::Display::default() {
        let backend_ = match display.type_().name() {
            "GdkX11Display" => "X11",
            "GdkWaylandDisplay" => "Wayland",
            "GdkBroadwayDisplay" => "Broadway",
            "GdkMacosDisplay" => "macOS",
            back => back,
        };
        backend.push_str(backend_);

        let surface = gdk::Surface::new_toplevel(&display);
        if let Some(gsk_renderer) = gtk::gsk::Renderer::for_surface(&surface) {
            let rend = match gsk_renderer.type_().name() {
                "GskVulkanRenderer" => "Vulkan",
                "GskNglRenderer" => "NGL",
                "GskGLRenderer" => "GL",
                "GskCairoRenderer" => "Cairo",
                rend => rend,
            };
            renderer.push_str(rend);
            gsk_renderer.unrealize(); // Raise --> GLib-GObject-CRITICAL **: 01:27:13.178: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
        }
        surface.destroy();
    }
    (backend, renderer)
}

The issue is that it raises the non fatal trace

GLib-GObject-CRITICAL **: 01:27:13.178: g_object_unref: assertion 'G_IS_OBJECT

My guess is that it should call g_object_unref (gsk_renderer);, but I'm failing to.

Is it possible that gtk::gsk::Renderer shall implement the Drop trait that will call g_object_unref?

Thanks for this wonderful framework.

[bilelmoussaoui]

That is because you are calling unrealize without realize?

[plrigaux]

If I remove/comment this line

gsk_renderer.unrealize();

The program crash with this error

**
Gsk:ERROR:../gtk/gsk/gskrenderer.c:130:gsk_renderer_dispose: assertion failed: (!priv->is_realized)
Bail out! Gsk:ERROR:../gtk/gsk/gskrenderer.c:130:gsk_renderer_dispose: assertion failed: (!priv->is_realized)

I like I said I translate the code from https://gitlab.gnome.org/GNOME/libadwaita/-/blob/main/demo/adw-demo-debug-info.c

More specificaly

/* Copied and adapted from gtk/inspector/general.c */
static void
get_gtk_info (const char **backend,
              const char **renderer)
{
  GdkDisplay *display = gdk_display_get_default ();
  GdkSurface *surface;
  GskRenderer *gsk_renderer;

  if (!g_strcmp0 (G_OBJECT_TYPE_NAME (display), "GdkX11Display"))
    *backend = "X11";
  else if (!g_strcmp0 (G_OBJECT_TYPE_NAME (display), "GdkWaylandDisplay"))
    *backend = "Wayland";
  else if (!g_strcmp0 (G_OBJECT_TYPE_NAME (display), "GdkBroadwayDisplay"))
    *backend = "Broadway";
  else if (!g_strcmp0 (G_OBJECT_TYPE_NAME (display), "GdkWin32Display"))
    *backend = "Windows";
  else if (!g_strcmp0 (G_OBJECT_TYPE_NAME (display), "GdkMacosDisplay"))
    *backend = "macOS";
  else
    *backend = G_OBJECT_TYPE_NAME (display);

  surface = gdk_surface_new_toplevel (display);
  gsk_renderer = gsk_renderer_new_for_surface (surface);
  if (!g_strcmp0 (G_OBJECT_TYPE_NAME (gsk_renderer), "GskVulkanRenderer"))
    *renderer = "Vulkan";
  else if (!g_strcmp0 (G_OBJECT_TYPE_NAME (gsk_renderer), "GskNglRenderer"))
    *renderer = "NGL";
  else if (!g_strcmp0 (G_OBJECT_TYPE_NAME (gsk_renderer), "GskGLRenderer"))
    *renderer = "GL";
  else if (!g_strcmp0 (G_OBJECT_TYPE_NAME (gsk_renderer), "GskCairoRenderer"))
    *renderer = "Cairo";
  else
    *renderer = G_OBJECT_TYPE_NAME (gsk_renderer);

  gsk_renderer_unrealize (gsk_renderer);
  g_object_unref (gsk_renderer);
  gdk_surface_destroy (surface);
}

As you can see there is no realize call in this code, but it does g_object_unref (gsk_renderer); witch I don't know how to reproduce since most of the time gtk-rs does it through the drop call.