cssvalue: Add _gtk_css_value_equal()

For now, we return FALSE for all default css values, so this is not very
useful.

I also think of this as an optimization equal, not a guaranteed equal,
because we don't even have a notion of what "equal" means.

For example, for background-repeat, "repeat, repeat" and "repeat"
are functionally equivalent. But the cssvalue has no idea that it's used
for background-repeat.
As a more complicated example, "repeat, no-repeat" and "repeat" are
equal to what one sees as long as there's only one image listed
background-image-source. But once you start transition'ing to an image
with 2 sources, it's different...

1 files changed, 21 insertions, 0 deletions

diff --git a/gtk/gtkcssvalue.c b/gtk/gtkcssvalue.c
index a797f65534..be0d71afdb 100644
--- a/gtk/gtkcssvalue.c
+++ b/gtk/gtkcssvalue.c
@@ -79,6 +79,13 @@ gtk_css_value_default_free (GtkCssValue *value)
   g_slice_free (GtkCssValue, value);
 }
 
+static gboolean
+gtk_css_value_default_equal (const GtkCssValue *value1,
+                             const GtkCssValue *value2)
+{
+  return FALSE;
+}
+
 static void
 gtk_css_value_default_print (const GtkCssValue *value,
                              GString           *string)
@@ -92,6 +99,7 @@ gtk_css_value_default_print (const GtkCssValue *value,
 
 static const GtkCssValueClass GTK_CSS_VALUE_DEFAULT = {
   gtk_css_value_default_free,
+  gtk_css_value_default_equal,
   gtk_css_value_default_print
 };
 
@@ -438,6 +446,19 @@ _gtk_css_value_unref (GtkCssValue *value)
   value->class->free (value);
 }
 
+gboolean
+_gtk_css_value_equal (const GtkCssValue *value1,
+                      const GtkCssValue *value2)
+{
+  g_return_val_if_fail (value1 != NULL, FALSE);
+  g_return_val_if_fail (value2 != NULL, FALSE);
+
+  if (value1->class != value2->class)
+    return FALSE;
+
+  return value1->class->equal (value1, value2);
+}
+
 void
 _gtk_css_value_print (const GtkCssValue *value,
                       GString           *string)