css: Track hover state changes separately

The idea is that this reduce the amount of frequently
changing state that css nodes are sensitive to.

This is going to reduce the amount of style recomputation.

1 files changed, 13 insertions, 1 deletions

diff --git a/gtk/gtkcssnode.c b/gtk/gtkcssnode.c
index 0cce324e05..cdc72d1881 100644
--- a/gtk/gtkcssnode.c
+++ b/gtk/gtkcssnode.c
@@ -1138,9 +1138,21 @@ void
 gtk_css_node_set_state (GtkCssNode    *cssnode,
                         GtkStateFlags  state_flags)
 {
+  GtkStateFlags old_state;
+
+  old_state = gtk_css_node_declaration_get_state (cssnode->decl);
+
   if (gtk_css_node_declaration_set_state (&cssnode->decl, state_flags))
     {
-      gtk_css_node_invalidate (cssnode, GTK_CSS_CHANGE_STATE);
+      GtkStateFlags states = old_state ^ state_flags;
+      GtkCssChange change = 0;
+
+      if (states & GTK_STATE_FLAG_PRELIGHT)
+        change |= GTK_CSS_CHANGE_HOVER;
+      if (states & ~GTK_STATE_FLAG_PRELIGHT)
+        change |= GTK_CSS_CHANGE_STATE;
+
+      gtk_css_node_invalidate (cssnode, change);
       g_object_notify_by_pspec (G_OBJECT (cssnode), cssnode_properties[PROP_STATE]);
     }
 }