add cli flag --alpha-layer

now that we have long-opts, we don't have to worry about exhausting the
alphabet list for short-opts. so adding a cli flag to set/unset the
checker background makes sense.

ref: https://codeberg.org/nsxiv/nsxiv/issues/404

1 files changed, 1 insertions, 0 deletions

diff --git a/nsxiv.h b/nsxiv.h
index 19e5399..ab3673f 100644
--- a/nsxiv.h
+++ b/nsxiv.h
@@ -241,6 +241,7 @@ struct opt {
 	float zoom;
 	bool animate;
 	bool anti_alias;
+	bool alpha_layer;
 	int gamma;
 	unsigned int slideshow;
 	int framerate;