Add GtkStyleProvider, an interface to provide style details.

The get_style() function isn't final yet, further parameters
should be added to query details based on the widget hierarchy,
name, etc.

gtk/gtkstyleprovider.h

@@ -0,0 +1,58 @@
+/* GTK - The GIMP Toolkit
+ * Copyright (C) 2010 Carlos Garnacho <carlosg@gnome.org>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#ifndef __GTK_STYLE_PROVIDER_H__
+#define __GTK_STYLE_PROVIDER_H__
+
+#include <glib-object.h>
+#include "gtkstyleset.h"
+#include "gtkenums.h"
+
+G_BEGIN_DECLS
+
+#define GTK_TYPE_STYLE_PROVIDER          (gtk_style_provider_get_type ())
+#define GTK_STYLE_PROVIDER(o)            (G_TYPE_CHECK_INSTANCE_CAST ((o), GTK_TYPE_STYLE_PROVIDER, GtkStyleProvider))
+#define GTK_IS_STYLE_PROVIDER(o)         (G_TYPE_CHECK_INSTANCE_TYPE ((o), GTK_TYPE_STYLE_PROVIDER))
+#define GTK_STYLE_PROVIDER_GET_IFACE(o)  (G_TYPE_INSTANCE_GET_INTERFACE ((o), GTK_TYPE_STYLE_PROVIDER, GtkStyleProviderIface))
+
+typedef struct GtkStyleProviderIface GtkStyleProviderIface;
+typedef struct GtkStyleProvider GtkStyleProvider; /* dummy typedef */
+
+typedef enum {
+  GTK_SELECTOR_TYPE_PATH,
+  GTK_SELECTOR_TYPE_NAME,
+  GTK_SELECTOR_TYPE_CLASS_PATH,
+  GTK_SELECTOR_TYPE_CLASS_NAME
+} GtkSelectorType;
+
+struct GtkStyleProviderIface
+{
+  GTypeInterface g_iface;
+
+  GtkStyleSet * (* get_style) (GtkStyleProvider *provider);
+};
+
+GType gtk_style_provider_get_type (void) G_GNUC_CONST;
+
+GtkStyleSet *gtk_style_provider_get_style (GtkStyleProvider *provider);
+
+
+G_END_DECLS
+
+#endif /* __GTK_STYLE_PROVIDER_H__ */