[gtk/matthiasc/css-change-tracking-2: 1/2] css: Don't got to the selector tree for change

[Matthias Clasen <matthiasc src gnome org>]

commit 1caf197a0db48df92b361218bba1e40ae7730faf
Author: Matthias Clasen <mclasen redhat com>
Date:   Wed Jan 15 08:03:09 2020 -0500

    css: Don't got to the selector tree for change
    
    The tree is optimized for mimizing the decisions, and is built ahead-of-time.
    That prevents us from taking advantage of the information in the matcher when
    collecting changes.
    
    So, instead do what we used to do for verification: Use the selector tree
    for finding the superset matches, then just walk the rulesets to collect
    the changes.
    
    Since we are now recomputing the change masks much less frequently, this
    slightly less optimized way of computing them is not a problem, and will
    let us compute better results in the future, by improving the superset
    matcher to be more precise.

 gtk/gtkcssprovider.c | 94 ++++++++++++++++++----------------------------------
 1 file changed, 33 insertions(+), 61 deletions(-)
---
diff --git a/gtk/gtkcssprovider.c b/gtk/gtkcssprovider.c
index 3713b83529..59573ebb34 100644
--- a/gtk/gtkcssprovider.c
+++ b/gtk/gtkcssprovider.c
@@ -425,61 +425,40 @@ verify_tree_match_results (GtkCssProvider *provider,
 #endif
 }
 
-static void
-verify_tree_get_change_results (GtkCssProvider *provider,
-                               const GtkCssMatcher *matcher,
-                               GtkCssChange change)
+/* Compute the change flags for a given matcher.
+ * We assume that name, id and classes stay unchanged, and look for all rules
+ * that can be matched if anything else changes. We collect the change masks
+ * from the selectors of these rules.
+ */
+static GtkCssChange
+compute_change (GtkCssProvider      *provider,
+                const GtkCssMatcher *matcher)
 {
-#ifdef VERIFY_TREE
-  {
-    GtkCssProviderPrivate *priv = gtk_css_provider_get_instance_private (provider);
-    GtkCssChange verify_change = 0;
-    GPtrArray *tree_rules;
-    int i;
-
-    tree_rules = _gtk_css_selector_tree_match_all (priv->tree, matcher);
-    if (tree_rules)
-      {
-        verify_tree_match_results (provider, matcher, tree_rules);
-
-        for (i = tree_rules->len - 1; i >= 0; i--)
-          {
-           GtkCssRuleset *ruleset;
-
-            ruleset = tree_rules->pdata[i];
-
-            verify_change |= _gtk_css_selector_get_change (ruleset->selector);
-          }
-
-        g_ptr_array_free (tree_rules, TRUE);
-      }
-
-    if (change != verify_change)
-      {
-       GString *s;
-
-       s = g_string_new ("");
-       g_string_append (s, "expected change ");
-        gtk_css_change_print (verify_change, s);
-        g_string_append (s, ", but it was ");
-        gtk_css_change_print (change, s);
-       if ((change & ~verify_change) != 0)
-          {
-           g_string_append (s, ", unexpectedly set: ");
-            gtk_css_change_print (change & ~verify_change, s);
-          }
-       if ((~change & verify_change) != 0)
-          {
-           g_string_append_printf (s, ", unexpectedly not set: ");
-            gtk_css_change_print (~change & verify_change, s);
-          }
-       g_warning (s->str);
-       g_string_free (s, TRUE);
-      }
-  }
-#endif
-}
+  GtkCssProviderPrivate *priv = gtk_css_provider_get_instance_private (provider);
+  GtkCssChange change = 0;
+  GPtrArray *tree_rules;
+  int i;
+  GtkCssMatcher change_matcher;
+
+  _gtk_css_matcher_superset_init (&change_matcher, matcher, GTK_CSS_CHANGE_NAME | GTK_CSS_CHANGE_CLASS);
 
+  tree_rules = _gtk_css_selector_tree_match_all (priv->tree, &change_matcher);
+  if (tree_rules)
+    {
+      for (i = tree_rules->len - 1; i >= 0; i--)
+        {
+         GtkCssRuleset *ruleset;
+
+          ruleset = tree_rules->pdata[i];
+
+          change |= _gtk_css_selector_get_change (ruleset->selector);
+        }
+
+      g_ptr_array_free (tree_rules, TRUE);
+   }
+
+  return change;
+}
 
 static GtkCssValue *
 gtk_css_style_provider_get_color (GtkStyleProvider *provider,
@@ -551,14 +530,7 @@ gtk_css_style_provider_lookup (GtkStyleProvider    *provider,
     }
 
   if (change)
-    {
-      GtkCssMatcher change_matcher;
-
-      _gtk_css_matcher_superset_init (&change_matcher, matcher, GTK_CSS_CHANGE_NAME | GTK_CSS_CHANGE_CLASS);
-
-      *change = _gtk_css_selector_tree_get_change_all (priv->tree, &change_matcher);
-      verify_tree_get_change_results (css_provider, &change_matcher, *change);
-    }
+    *change = compute_change (css_provider, matcher);
 }
 
 static void