st/image-content: Implement GIcon interface

On the one hand, this is a bit of a stretch: StImageContent is what
we create from GIcons.

But on the other hand, there's some justification: StImageContent does
represent an image (and likely icon) after all, and there's some
precedent with GdkPixbuf.

In the end as we don't care about serialization or loading from other
API, we can go with a very crude implementation that allows us to
pass out a content as GIcon and use it directly when "loading" it.

We will use that soon to represent X11 window icons as GIcons, which
in turn will allow us to unify app icon handling.

https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1342

src/st/st-image-content.c

@@ -42,11 +42,17 @@ enum
 };
 
 static void clutter_content_interface_init (ClutterContentInterface *iface);
+static void g_icon_interface_init (GIconIface *iface);
+static void g_loadable_icon_interface_init (GLoadableIconIface *iface);
 
 G_DEFINE_TYPE_WITH_CODE (StImageContent, st_image_content, CLUTTER_TYPE_IMAGE,
                          G_ADD_PRIVATE (StImageContent)
                          G_IMPLEMENT_INTERFACE (CLUTTER_TYPE_CONTENT,
-                                                clutter_content_interface_init))
+                                                clutter_content_interface_init)
+                         G_IMPLEMENT_INTERFACE (G_TYPE_ICON,
+                                                g_icon_interface_init)
+                         G_IMPLEMENT_INTERFACE (G_TYPE_LOADABLE_ICON,
+                                                g_loadable_icon_interface_init))
 
 static void
 st_image_content_init (StImageContent *self)
@@ -165,12 +171,157 @@ st_image_content_get_preferred_size (ClutterContent *content,
   return TRUE;
 }
 
+static GdkPixbuf*
+pixbuf_from_image (StImageContent *image)
+{
+  CoglTexture *texture;
+  int width, height, rowstride;
+  uint8_t *data;
+
+  texture = clutter_image_get_texture (CLUTTER_IMAGE (image));
+  if (!texture || !cogl_texture_is_get_data_supported (texture))
+    return NULL;
+
+  width = cogl_texture_get_width (texture);
+  height = cogl_texture_get_width (texture);
+  rowstride = 4 * width;
+  data = g_new (uint8_t, rowstride * height);
+
+  cogl_texture_get_data (texture, COGL_PIXEL_FORMAT_RGBA_8888, rowstride, data);
+
+  return gdk_pixbuf_new_from_data ((const guchar *)data,
+                                   GDK_COLORSPACE_RGB,
+                                   TRUE, 8, width, height, rowstride,
+                                   (GdkPixbufDestroyNotify)g_free, NULL);
+}
+
 static void
 clutter_content_interface_init (ClutterContentInterface *iface)
 {
   iface->get_preferred_size = st_image_content_get_preferred_size;
 }
 
+static guint
+st_image_content_hash (GIcon *icon)
+{
+  return g_direct_hash (icon);
+}
+
+static gboolean
+st_image_content_equal (GIcon *icon1,
+                        GIcon *icon2)
+{
+  return g_direct_equal (icon1, icon2);
+}
+
+static GVariant *
+st_image_content_serialize (GIcon *icon)
+{
+  g_autoptr (GdkPixbuf) pixbuf = NULL;
+
+  pixbuf = pixbuf_from_image (ST_IMAGE_CONTENT (icon));
+  if (!pixbuf)
+    return NULL;
+
+  return g_icon_serialize (G_ICON (pixbuf));
+}
+
+static void
+g_icon_interface_init (GIconIface *iface)
+{
+  iface->hash = st_image_content_hash;
+  iface->equal = st_image_content_equal;
+  iface->serialize = st_image_content_serialize;
+}
+
+static GInputStream *
+st_image_load (GLoadableIcon  *icon,
+               int             size,
+               char          **type,
+               GCancellable   *cancellable,
+               GError       **error)
+{
+  g_autoptr (GdkPixbuf) pixbuf = NULL;
+
+  pixbuf = pixbuf_from_image (ST_IMAGE_CONTENT (icon));
+  if (!pixbuf)
+    {
+      g_set_error_literal (error, G_IO_ERROR, G_IO_ERROR_FAILED,
+                           "Failed to read texture");
+      return NULL;
+    }
+
+  return g_loadable_icon_load (G_LOADABLE_ICON (pixbuf),
+                               size, type, cancellable, error);
+}
+
+static void
+load_image_thread (GTask        *task,
+                   gpointer      object,
+                   gpointer      task_data,
+                   GCancellable *cancellable)
+{
+  GInputStream *stream;
+  GError *error = NULL;
+  char *type;
+
+  stream = st_image_load (G_LOADABLE_ICON (object),
+                          GPOINTER_TO_INT (task_data),
+                          &type,
+                          cancellable,
+                          &error);
+
+  if (error)
+    {
+      g_task_return_error (task, error);
+    }
+  else
+    {
+      g_task_set_task_data (task, type, g_free);
+      g_task_return_pointer (task, stream, g_object_unref);
+    }
+}
+
+static void
+st_image_load_async (GLoadableIcon       *icon,
+                     int                  size,
+                     GCancellable        *cancellable,
+                     GAsyncReadyCallback  callback,
+                     gpointer             user_data)
+{
+  g_autoptr (GTask) task = NULL;
+
+  task = g_task_new (icon, cancellable, callback, user_data);
+  g_task_set_task_data (task, GINT_TO_POINTER (size), NULL);
+  g_task_run_in_thread (task, load_image_thread);
+}
+
+static GInputStream *
+st_image_load_finish (GLoadableIcon  *icon,
+                      GAsyncResult   *res,
+                      char          **type,
+                      GError        **error)
+{
+  GInputStream *stream;
+
+  stream = g_task_propagate_pointer (G_TASK (res), error);
+  if (!stream)
+    return NULL;
+
+  if (type)
+    *type = g_strdup (g_task_get_task_data (G_TASK (res)));
+
+  return stream;
+}
+
+static void
+g_loadable_icon_interface_init (GLoadableIconIface *iface)
+{
+  iface->load = st_image_load;
+  iface->load_async = st_image_load_async;
+  iface->load_finish = st_image_load_finish;
+}
+
 /**
  * st_image_content_new_with_preferred_size:
  * @width: The preferred width to be used when drawing the content

src/st/st-texture-cache.c

@@ -981,6 +981,18 @@ st_texture_cache_load_gicon (StTextureCache    *cache,
   StIconStyle icon_style = ST_ICON_STYLE_REQUESTED;
   GtkIconLookupFlags lookup_flags;
 
+  actor_size = size * paint_scale;
+
+  if (ST_IS_IMAGE_CONTENT (icon))
+    {
+      return g_object_new (CLUTTER_TYPE_ACTOR,
+                           "request-mode", CLUTTER_REQUEST_CONTENT_SIZE,
+                           "width", actor_size,
+                           "height", actor_size,
+                           "content", CLUTTER_CONTENT (icon),
+                           NULL);
+    }
+
   if (theme_node)
     {
       colors = st_theme_node_get_icon_colors (theme_node);
@@ -1034,7 +1046,6 @@ st_texture_cache_load_gicon (StTextureCache    *cache,
   g_free (gicon_string);
 
   actor = create_invisible_actor ();
-  actor_size = size * paint_scale;
   clutter_actor_set_size (actor, actor_size, actor_size);
   if (ensure_request (cache, key, policy, &request, actor))
     {