[gtk+] cssnode: Catch case where a style didn't change

[Benjamin Otte <otte src gnome org>]

commit 2c613166771ea9118ebda91c311f11b3462330fb
Author: Benjamin Otte <otte redhat com>
Date:   Sat Dec 12 02:09:01 2015 +0100

    cssnode: Catch case where a style didn't change
    
    Catch the case where a CSS style did not change and don't emit the
    style-changed signal in that case.
    
    This saves not only the emission of the signal, but also doesn't cause
    invalidation in child nodes, which would previously get a PARENT_STYLE

 gtk/gtkcssnode.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)
---
diff --git a/gtk/gtkcssnode.c b/gtk/gtkcssnode.c
index 9df217a..ec89634 100644
--- a/gtk/gtkcssnode.c
+++ b/gtk/gtkcssnode.c
@@ -950,17 +950,20 @@ gtk_css_node_set_style (GtkCssNode  *cssnode,
                         GtkCssStyle *style)
 {
   GtkCssStyleChange change;
+  gboolean style_changed;
 
   if (cssnode->style == style)
     return FALSE;
 
   gtk_css_style_change_init (&change, cssnode->style, style);
 
-  g_signal_emit (cssnode, cssnode_signals[STYLE_CHANGED], 0, &change);
+  style_changed = gtk_css_style_change_has_change (&change);
+  if (style_changed)
+    g_signal_emit (cssnode, cssnode_signals[STYLE_CHANGED], 0, &change);
 
   gtk_css_style_change_finish (&change);
 
-  return TRUE;
+  return style_changed;
 }
 
 static void