[mutter] shaped-texture: Mark set the clip and return value nullable

[Jonas Ådahl <jadahl src gnome org>]

commit 82901f89d525db86c13821f9f9424f87b5f668b9
Author: Marco Trevisan (Treviño) <mail 3v1n0 net>
Date:   Fri Sep 13 06:00:35 2019 +0200

    shaped-texture: Mark set the clip and return value nullable
    
    As per the code definition the clip can be a null rectangle, and we can also
    return a null surface, so mark them as nullable in the introspection.
    
    https://gitlab.gnome.org/GNOME/mutter/merge_requests/796

 src/compositor/meta-shaped-texture.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/src/compositor/meta-shaped-texture.c b/src/compositor/meta-shaped-texture.c
index f85b55e23..972c33606 100644
--- a/src/compositor/meta-shaped-texture.c
+++ b/src/compositor/meta-shaped-texture.c
@@ -1204,7 +1204,7 @@ get_image_via_offscreen (MetaShapedTexture     *stex,
 /**
  * meta_shaped_texture_get_image:
  * @stex: A #MetaShapedTexture
- * @clip: A clipping rectangle, to help prevent extra processing.
+ * @clip: (nullable): A clipping rectangle, to help prevent extra processing.
  * In the case that the clipping rectangle is partially or fully
  * outside the bounds of the texture, the rectangle will be clipped.
  *
@@ -1212,7 +1212,7 @@ get_image_via_offscreen (MetaShapedTexture     *stex,
  * image by alpha blending the two images, and returns the flattened
  * image.
  *
- * Returns: (transfer full): a new cairo surface to be freed with
+ * Returns: (nullable) (transfer full): a new cairo surface to be freed with
  * cairo_surface_destroy().
  */
 cairo_surface_t *