a11y: Do not notify of empty state changes

If the ATContext state hasn't changed—for instance, if the accessible
attributes have been set to their default value, or have been set to the
same value—do not emit an accessible state change. State changes can be
arbitrarily expensive, so we want to ensure that they are meaningful.

1 files changed, 31 insertions, 6 deletions

diff --git a/gtk/gtkatcontext.c b/gtk/gtkatcontext.c
index 9cdbd0e9f3..e1e2edd599 100644
--- a/gtk/gtkatcontext.c
+++ b/gtk/gtkatcontext.c
@@ -425,6 +425,12 @@ gtk_at_context_update (GtkATContext *self)
 {
   g_return_if_fail (GTK_IS_AT_CONTEXT (self));
 
+  /* There's no point in notifying of state changes if there weren't any */
+  if (self->updated_properties == 0 &&
+      self->updated_relations == 0 &&
+      self->updated_states == 0)
+    return;
+
   GtkAccessibleStateChange changed_states =
     gtk_accessible_attribute_set_get_changed (self->states);
   GtkAccessiblePropertyChange changed_properties =
@@ -435,6 +441,10 @@ gtk_at_context_update (GtkATContext *self)
   g_signal_emit (self, obj_signals[STATE_CHANGE], 0,
                  changed_states, changed_properties, changed_relations,
                  self->states, self->properties, self->relations);
+
+  self->updated_properties = 0;
+  self->updated_relations = 0;
+  self->updated_states = 0;
 }
 
 /*< private >
@@ -457,10 +467,15 @@ gtk_at_context_set_accessible_state (GtkATContext       *self,
 {
   g_return_if_fail (GTK_IS_AT_CONTEXT (self));
 
+  gboolean res = FALSE;
+
   if (value != NULL)
-    gtk_accessible_attribute_set_add (self->states, state, value);
+    res = gtk_accessible_attribute_set_add (self->states, state, value);
   else
-    gtk_accessible_attribute_set_remove (self->states, state);
+    res = gtk_accessible_attribute_set_remove (self->states, state);
+
+  if (res)
+    self->updated_states |= (1 << state);
 }
 
 /*< private >
@@ -519,10 +534,15 @@ gtk_at_context_set_accessible_property (GtkATContext          *self,
 {
   g_return_if_fail (GTK_IS_AT_CONTEXT (self));
 
+  gboolean res = FALSE;
+
   if (value != NULL)
-    gtk_accessible_attribute_set_add (self->properties, property, value);
+    res = gtk_accessible_attribute_set_add (self->properties, property, value);
   else
-    gtk_accessible_attribute_set_remove (self->properties, property);
+    res = gtk_accessible_attribute_set_remove (self->properties, property);
+
+  if (res)
+    self->updated_properties |= (1 << property);
 }
 
 /*< private >
@@ -581,10 +601,15 @@ gtk_at_context_set_accessible_relation (GtkATContext          *self,
 {
   g_return_if_fail (GTK_IS_AT_CONTEXT (self));
 
+  gboolean res = FALSE;
+
   if (value != NULL)
-    gtk_accessible_attribute_set_add (self->relations, relation, value);
+    res = gtk_accessible_attribute_set_add (self->relations, relation, value);
   else
-    gtk_accessible_attribute_set_remove (self->relations, relation);
+    res = gtk_accessible_attribute_set_remove (self->relations, relation);
+
+  if (res)
+    self->updated_relations |= (1 << relation);
 }
 
 /*< private >