stylecontext: add gtk_render_icon_surface

This draws an icon from a cairo_surface. We want to use this more rather
than render_icon as this means we can skip the pixbuf to surface
conversion (including allocation and alpha premultiplication) at
render time, plus we can use create_similar_image which may allow
faster rendering.

gtk/gtkstylecontext.c

@@ -4512,6 +4512,42 @@ gtk_render_icon (GtkStyleContext *context,
   cairo_restore (cr);
 }
 
+/**
+ * gtk_render_icon_surface:
+ * @context: a #GtkStyleContext
+ * @cr: a #cairo_t
+ * @surface: a #cairo_surface_t containing the icon to draw
+ * @x: X position for the @icon
+ * @y: Y position for the @incon
+ *
+ * Renders the icon in @surface at the specified @x and @y coordinates.
+ *
+ * Since: 3.10
+ **/
+void
+gtk_render_icon_surface (GtkStyleContext *context,
+			 cairo_t         *cr,
+			 cairo_surface_t *surface,
+			 gdouble          x,
+			 gdouble          y)
+{
+  GtkThemingEngineClass *engine_class;
+  GtkThemingEngine *engine;
+
+  g_return_if_fail (GTK_IS_STYLE_CONTEXT (context));
+  g_return_if_fail (cr != NULL);
+
+  engine = _gtk_css_engine_value_get_engine (_gtk_style_context_peek_property (context, GTK_CSS_PROPERTY_ENGINE));
+  engine_class = GTK_THEMING_ENGINE_GET_CLASS (engine);
+
+  cairo_save (cr);
+
+  _gtk_theming_engine_set_context (engine, context);
+  engine_class->render_icon_surface (engine, cr, surface, x, y);
+
+  cairo_restore (cr);
+}
+
 static void
 draw_insertion_cursor (GtkStyleContext *context,
                        cairo_t         *cr,

gtk/gtkstylecontext.h

@@ -1090,6 +1090,12 @@ void        gtk_render_icon        (GtkStyleContext     *context,
                                     GdkPixbuf           *pixbuf,
                                     gdouble              x,
                                     gdouble              y);
+GDK_AVAILABLE_IN_3_10
+void        gtk_render_icon_surface (GtkStyleContext    *context,
+				     cairo_t            *cr,
+				     cairo_surface_t    *surface,
+				     gdouble             x,
+				     gdouble             y);
 GDK_AVAILABLE_IN_3_4
 void        gtk_render_insertion_cursor
                                    (GtkStyleContext     *context,

gtk/gtkthemingengine.c

@@ -182,6 +182,11 @@ static void gtk_theming_engine_render_icon (GtkThemingEngine *engine,
 					    GdkPixbuf *pixbuf,
                                             gdouble x,
                                             gdouble y);
+static void gtk_theming_engine_render_icon_surface (GtkThemingEngine *engine,
+						    cairo_t *cr,
+						    cairo_surface_t *surface,
+						    gdouble x,
+						    gdouble y);
 
 G_DEFINE_TYPE (GtkThemingEngine, gtk_theming_engine, G_TYPE_OBJECT)
 
@@ -239,6 +244,7 @@ gtk_theming_engine_class_init (GtkThemingEngineClass *klass)
   klass->render_handle = gtk_theming_engine_render_handle;
   klass->render_activity = gtk_theming_engine_render_activity;
   klass->render_icon_pixbuf = gtk_theming_engine_render_icon_pixbuf;
+  klass->render_icon_surface = gtk_theming_engine_render_icon_surface;
 
   /**
    * GtkThemingEngine:name:
@@ -2791,3 +2797,21 @@ gtk_theming_engine_render_icon (GtkThemingEngine *engine,
   cairo_restore (cr);
 }
 
+static void
+gtk_theming_engine_render_icon_surface (GtkThemingEngine *engine,
+					cairo_t *cr,
+					cairo_surface_t *surface,
+					gdouble x,
+					gdouble y)
+{
+  cairo_save (cr);
+
+  cairo_set_source_surface (cr, surface, x, y);
+
+  _gtk_css_shadows_value_paint_icon (_gtk_theming_engine_peek_property (engine, GTK_CSS_PROPERTY_ICON_SHADOW), cr);
+
+  cairo_paint (cr);
+
+  cairo_restore (cr);
+}
+

gtk/gtkthemingengine.h

@@ -70,6 +70,7 @@ struct _GtkThemingEngine
  *                   or #GtkProgressBar.
  * @render_icon_pixbuf: Renders an icon as a #GdkPixbuf.
  * @render_icon: Renders an icon given as a #GdkPixbuf.
+ * @render_icon_surface: Renders an icon given as a #cairo_surface_t.
  *
  * Base class for theming engines.
  */
@@ -174,9 +175,14 @@ struct _GtkThemingEngineClass
 			GdkPixbuf        *pixbuf,
                         gdouble           x,
                         gdouble           y);
+  void (* render_icon_surface) (GtkThemingEngine *engine,
+				cairo_t          *cr,
+				cairo_surface_t  *surface,
+				gdouble           x,
+				gdouble           y);
 
   /*< private >*/
-  gpointer padding[15];
+  gpointer padding[14];
 };
 
 GDK_AVAILABLE_IN_ALL