cogl-bitmap: Add a public accessor for the underlying pixel buffer

This adds a small cogl_bitmap_get_buffer public function. Note that
this can return NULL if the bitmap was not created with a pixel
buffer. It might be nice to change this eventually so that all bitmaps
have a pixel buffer.

Reviewed-by: Robert Bragg <robert@linux.intel.com>

cogl/cogl-bitmap.c

@@ -330,6 +330,15 @@ cogl_bitmap_get_rowstride (CoglBitmap *bitmap)
   return bitmap->rowstride;
 }
 
+CoglPixelBuffer *
+cogl_bitmap_get_buffer (CoglBitmap *bitmap)
+{
+  while (bitmap->shared_bmp)
+    bitmap = bitmap->shared_bmp;
+
+  return COGL_PIXEL_BUFFER (bitmap->buffer);
+}
+
 GQuark
 cogl_bitmap_error_quark (void)
 {

cogl/cogl-bitmap.h

@@ -31,6 +31,7 @@
 #include <cogl/cogl-types.h>
 #include <cogl/cogl-buffer.h>
 #include <cogl/cogl-context.h>
+#include <cogl/cogl-pixel-buffer.h>
 
 G_BEGIN_DECLS
 
@@ -174,6 +175,20 @@ cogl_bitmap_get_height (CoglBitmap *bitmap);
 int
 cogl_bitmap_get_rowstride (CoglBitmap *bitmap);
 
+/**
+ * cogl_bitmap_get_buffer:
+ * @bitmap: A #CoglBitmap
+ *
+ * Return value: the #CoglPixelBuffer that this buffer uses for
+ *   storage. Note that if the bitmap was created with
+ *   cogl_bitmap_new_from_file() then it will not actually be using a
+ *   pixel buffer and this function will return %NULL.
+ * Stability: unstable
+ * Since: 1.10
+ */
+CoglPixelBuffer *
+cogl_bitmap_get_buffer (CoglBitmap *bitmap);
+
 #endif /* COGL_ENABLE_EXPERIMENTAL_API */
 
 /**