[gtk/clipboard-emo] gtk-demo: Fix up image handling in the clipboard demo

[Matthias Clasen <matthiasc src gnome org>]

commit 8cf955731fd6c5ac36c8b590dad0fb1de9482af3
Author: Matthias Clasen <mclasen redhat com>
Date:   Thu Oct 15 09:16:17 2020 -0400

    gtk-demo: Fix up image handling in the clipboard demo
    
    Using GtkIconPaintable+GtkPicture is not good for symbolic
    icons - they don't get properly colored that way. So change
    things around to use the icon name if we have it.
    
    Fixes: #3252

 demos/gtk-demo/demoimage.c | 40 +++++++++++++++++++++++++++++++++-------
 1 file changed, 33 insertions(+), 7 deletions(-)
---
diff --git a/demos/gtk-demo/demoimage.c b/demos/gtk-demo/demoimage.c
index 40acbd2dce..a7ecb6e213 100644
--- a/demos/gtk-demo/demoimage.c
+++ b/demos/gtk-demo/demoimage.c
@@ -47,6 +47,38 @@ get_image_paintable (GtkImage *image)
     }
 }
 
+static void
+update_drag_icon (DemoImage   *demo,
+                  GtkDragIcon *icon)
+{
+  const char *icon_name;
+  GdkPaintable *paintable;
+  GtkWidget *image;
+
+  switch (gtk_image_get_storage_type (GTK_IMAGE (demo->image)))
+    {
+    case GTK_IMAGE_PAINTABLE:
+      paintable = gtk_image_get_paintable (GTK_IMAGE (demo->image));
+      image = gtk_image_new_from_paintable (paintable);
+      break;
+    case GTK_IMAGE_ICON_NAME:
+      icon_name = gtk_image_get_icon_name (GTK_IMAGE (demo->image));
+      image = gtk_image_new_from_icon_name (icon_name);
+      break;
+    case GTK_IMAGE_EMPTY:
+    case GTK_IMAGE_GICON:
+    default:
+      g_warning ("Image storage type %d not handled",
+                 gtk_image_get_storage_type (GTK_IMAGE (demo->image)));
+      return;
+    }
+
+  gtk_image_set_pixel_size (GTK_IMAGE (image),
+                            gtk_image_get_pixel_size (GTK_IMAGE (demo->image)));
+
+  gtk_drag_icon_set_child (icon, image);
+}
+
 static void
 drag_begin (GtkDragSource *source,
             GdkDrag       *drag,
@@ -54,14 +86,8 @@ drag_begin (GtkDragSource *source,
 {
   GtkWidget *widget = gtk_event_controller_get_widget (GTK_EVENT_CONTROLLER (source));
   DemoImage *demo = DEMO_IMAGE (widget);
-  GdkPaintable *paintable;
 
-  paintable = get_image_paintable (GTK_IMAGE (demo->image));
-  if (paintable)
-    {
-      gtk_drag_icon_set_from_paintable (drag, paintable, -2, -2);
-      g_object_unref (paintable);
-    }
+  update_drag_icon (demo, GTK_DRAG_ICON (gtk_drag_icon_get_for_drag (drag)));
 }
 
 static GdkContentProvider *