[gtk+] cssimage: Fix cross-fade

[Benjamin Otte <otte src gnome org>]

commit 4c7ddbf519db17010328b4ffaba994f5b6a9f94c
Author: Benjamin Otte <otte redhat com>
Date:   Wed Jan 11 02:51:50 2017 +0100

    cssimage: Fix cross-fade
    
    Simgle image cross-fade opacity was computed the wrong way, which caused
    weird fade-in/out animations, for example in flat buttons.
    
    I messed this up when porting cross-fades to snapshot().

 gtk/gtkcssimagecrossfade.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/gtk/gtkcssimagecrossfade.c b/gtk/gtkcssimagecrossfade.c
index 546c272..60e9224 100644
--- a/gtk/gtkcssimagecrossfade.c
+++ b/gtk/gtkcssimagecrossfade.c
@@ -150,14 +150,14 @@ gtk_css_image_cross_fade_snapshot (GtkCssImage *image,
         }
       else if (start_node)
         {
-          gtk_snapshot_push_opacity (snapshot, cross_fade->progress, "CrossFadeStart");
+          gtk_snapshot_push_opacity (snapshot, 1.0 - cross_fade->progress, "CrossFadeStart");
           gtk_snapshot_append_node (snapshot, start_node);
           gtk_snapshot_pop_and_append (snapshot);
           gsk_render_node_unref (start_node);
         }
       else if (end_node)
         {
-          gtk_snapshot_push_opacity (snapshot, 1.0 - cross_fade->progress, "CrossFadeEnd");
+          gtk_snapshot_push_opacity (snapshot, cross_fade->progress, "CrossFadeEnd");
           gtk_snapshot_append_node (snapshot, end_node);
           gtk_snapshot_pop_and_append (snapshot);
           gsk_render_node_unref (end_node);