libweston: add pixel_format_get_info_by_pixman()

Sometimes you will have a pixman_image_t and you need the corresponding
drm_fourcc format.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>

libweston/pixel-formats.c

@@ -636,6 +636,19 @@ pixel_format_get_info_by_drm_name(const char *drm_format_name)
 	return NULL;
 }
 
+WL_EXPORT const struct pixel_format_info *
+pixel_format_get_info_by_pixman(pixman_format_code_t pixman_format)
+{
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_LENGTH(pixel_format_table); i++) {
+		if (pixel_format_table[i].pixman_format == pixman_format)
+			return &pixel_format_table[i];
+	}
+
+	return NULL;
+}
+
 WL_EXPORT unsigned int
 pixel_format_get_plane_count(const struct pixel_format_info *info)
 {

libweston/pixel-formats.h

@@ -190,6 +190,19 @@ pixel_format_get_info_count(void);
 const struct pixel_format_info *
 pixel_format_get_info_by_drm_name(const char *drm_format_name);
 
+/**
+ * Get pixel format information for a Pixman format code
+ *
+ * Given a Pixman format code, return a pixel format info structure describing
+ * the properties of that format.
+ *
+ * @param pixman_format Pixman format code to get info for
+ * @returns A pixel format structure (must not be freed), or NULL if the
+ *          format could not be found
+ */
+const struct pixel_format_info *
+pixel_format_get_info_by_pixman(pixman_format_code_t pixman_format);
+
 /**
  * Get number of planes used by a pixel format
  *