[gtk+/gtk-3-22] cssnode: Don't put wrong styles in the style cache

[Timm Bäder <baedert src gnome org>]

commit 8439f06500ba4e6f4a7b52351e67c579509ef903
Author: Benjamin Otte <otte redhat com>
Date:   Tue Oct 10 21:00:46 2017 +0200

    cssnode: Don't put wrong styles in the style cache
    
    ~Company ╡ so TL;DR: we put the static style in the cache, but then
           ⤷ ╡ compute a child style from the animated style in the cache
           ⤷ ╡ and we put the child style also in the cache (because
           ⤷ ╡ it's not animated)
           ⤷ ╡ then we run the animation, but reuse the cache every time
           ⤷ ╡ for both child and parent
           ⤷ ╡ so after the animation is done, we end up with a cache that
           ⤷ ╡ has the correct static style for the parent but an
           ⤷ ╡ incorrect static style for the child
           ⤷ ╡ because that static style was computed from the
           ⤷ ╡ initial animated style
    
    This fixes https://bugzilla.gnome.org/show_bug.cgi?id=763517

 gtk/gtkcssnode.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)
---
diff --git a/gtk/gtkcssnode.c b/gtk/gtkcssnode.c
index f68c1e1..1a9aa3e 100644
--- a/gtk/gtkcssnode.c
+++ b/gtk/gtkcssnode.c
@@ -434,6 +434,10 @@ gtk_css_node_real_update_style (GtkCssNode   *cssnode,
                                               timestamp,
                                               gtk_css_node_get_style_provider (cssnode),
                                               should_create_transitions (change) ? style : NULL);
+
+      /* Clear the cache again, the static style we looked up above
+       * may have populated it. */
+      g_clear_pointer (&cssnode->cache, gtk_css_node_style_cache_unref);
     }
   else if (static_style != style && (change & GTK_CSS_CHANGE_TIMESTAMP))
     {