[gtk+] iconhelper: Ensure the surface used for textures is ARGB32

[Timm Bäder <baedert src gnome org>]

commit 8a543ab23c541741f8ab3dd93e18c8d4fb17b312
Author: Timm Bäder <mail baedert org>
Date:   Fri Dec 2 17:32:12 2016 +0100

    iconhelper: Ensure the surface used for textures is ARGB32

 gtk/gtkiconhelper.c |   17 +++++++++++++++++
 1 files changed, 17 insertions(+), 0 deletions(-)
---
diff --git a/gtk/gtkiconhelper.c b/gtk/gtkiconhelper.c
index 5404a3c..fcf3bbe 100644
--- a/gtk/gtkiconhelper.c
+++ b/gtk/gtkiconhelper.c
@@ -565,6 +565,23 @@ gtk_icon_helper_ensure_texture (GtkIconHelper *self,
 
   scale = gtk_widget_get_scale_factor (gtk_css_gadget_get_owner (GTK_CSS_GADGET (self))),
   _gtk_icon_helper_get_size (self, &width, &height);
+
+  if (cairo_image_surface_get_format (self->priv->rendered_surface) != CAIRO_FORMAT_ARGB32)
+    {
+      cairo_surface_t *argb_surface = cairo_surface_create_similar_image (self->priv->rendered_surface,
+                                                                          CAIRO_FORMAT_ARGB32,
+                                                                          width, height);
+      cairo_t *ct;
+      cairo_surface_set_device_scale (argb_surface, scale, scale);
+
+      ct = cairo_create (argb_surface);
+      cairo_set_source_surface (ct, self->priv->rendered_surface, 0, 0);
+      cairo_paint (ct);
+      cairo_destroy (ct);
+      cairo_surface_destroy (self->priv->rendered_surface);
+      self->priv->rendered_surface = argb_surface;
+    }
+
   map = cairo_surface_map_to_image (self->priv->rendered_surface,
                                     &(GdkRectangle) { 0, 0, width * scale, height * scale});