rendernode: Make sure depth variable has enough bits

This will be relevant when we add new values to it.

gdk/gdkmemoryformat.c

@@ -28,6 +28,8 @@
 
 #include <epoxy/gl.h>
 
+G_STATIC_ASSERT ((1 << GDK_MEMORY_DEPTH_BITS) > GDK_N_DEPTHS);
+
 typedef struct _GdkMemoryFormatDescription GdkMemoryFormatDescription;
 
 #define TYPED_FUNCS(name, T, R, G, B, A, bpp, scale) \

gdk/gdkmemoryformatprivate.h

@@ -45,6 +45,8 @@ typedef enum {
   GDK_N_DEPTHS
 } GdkMemoryDepth;
 
+#define GDK_MEMORY_DEPTH_BITS 3
+
 gsize                   gdk_memory_format_alignment         (GdkMemoryFormat             format) G_GNUC_CONST;
 GdkMemoryAlpha          gdk_memory_format_alpha             (GdkMemoryFormat             format) G_GNUC_CONST;
 gsize                   gdk_memory_format_bytes_per_pixel   (GdkMemoryFormat             format) G_GNUC_CONST;

gsk/gskrendernodeprivate.h

@@ -32,7 +32,7 @@ struct _GskRenderNode
 
   graphene_rect_t bounds;
 
-  guint preferred_depth : 2;
+  guint preferred_depth : GDK_MEMORY_DEPTH_BITS;
   guint offscreen_for_opacity : 1;
 };