a11y: Pass on platform changes

Add an enum for 'platform changes' to the at context
change notification mechanism. This will let us pass
along things that ARIA considers 'platform state' such
as focus or editability. The difference between the
platform state and other ARIA states is that we don't
keep the platform state separately in the at context
- backends are expected to just query the widgets.

This is just about avoiding notify listeners for
change notification.

gtk/a11y/gtkatspicontext.c

@@ -644,6 +644,7 @@ gtk_at_spi_context_state_change (GtkATContext                *ctx,
                                  GtkAccessibleStateChange     changed_states,
                                  GtkAccessiblePropertyChange  changed_properties,
                                  GtkAccessibleRelationChange  changed_relations,
+                                 GtkAccessiblePlatformChange  changed_platform,
                                  GtkAccessibleAttributeSet   *states,
                                  GtkAccessibleAttributeSet   *properties,
                                  GtkAccessibleAttributeSet   *relations)

gtk/gtkaccessible.c

@@ -636,3 +636,16 @@ gtk_accessible_role_to_name (GtkAccessibleRole  role,
 
   return role_names[role];
 }
+
+void
+gtk_accessible_platform_changed (GtkAccessible               *self,
+                                 GtkAccessiblePlatformChange  change)
+{
+  GtkATContext *context = gtk_accessible_get_at_context (self);
+  if (context == NULL)
+    return;
+
+  gtk_at_context_platform_changed (context, change);
+  gtk_at_context_update (context);
+}
+

gtk/gtkaccessibleattributesetprivate.h

@@ -20,7 +20,7 @@
 
 #pragma once
 
-#include "gtkaccessibleprivate.h"
+#include "gtkaccessible.h"
 #include "gtkaccessiblevalueprivate.h"
 
 G_BEGIN_DECLS

gtk/gtkaccessibleprivate.h

@@ -21,7 +21,7 @@
 #pragma once
 
 #include "gtkaccessible.h"
-#include "gtkatcontext.h"
+#include "gtkatcontextprivate.h"
 
 G_BEGIN_DECLS
 
@@ -37,4 +37,7 @@ GtkATContext *  gtk_accessible_get_at_context   (GtkAccessible *self);
 const char *    gtk_accessible_role_to_name     (GtkAccessibleRole  role,
                                                  const char        *domain);
 
+void gtk_accessible_platform_changed (GtkAccessible               *self,
+                                      GtkAccessiblePlatformChange  change);
+
 G_END_DECLS

gtk/gtkatcontext.c

@@ -36,6 +36,7 @@
 #include "gtkatcontextprivate.h"
 
 #include "gtkaccessiblevalueprivate.h"
+#include "gtkaccessibleprivate.h"
 #include "gtkdebug.h"
 #include "gtktestatcontextprivate.h"
 #include "gtktypebuiltins.h"
@@ -137,6 +138,7 @@ gtk_at_context_real_state_change (GtkATContext                *self,
                                   GtkAccessibleStateChange     changed_states,
                                   GtkAccessiblePropertyChange  changed_properties,
                                   GtkAccessibleRelationChange  changed_relations,
+                                  GtkAccessiblePlatformChange  changed_platform,
                                   GtkAccessibleAttributeSet   *states,
                                   GtkAccessibleAttributeSet   *properties,
                                   GtkAccessibleAttributeSet   *relations)
@@ -505,7 +507,8 @@ gtk_at_context_update (GtkATContext *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)
+      self->updated_states == 0 &&
+      self->updated_platform == 0)
     return;
 
   GtkAccessibleStateChange changed_states =
@@ -517,12 +520,14 @@ gtk_at_context_update (GtkATContext *self)
 
   GTK_AT_CONTEXT_GET_CLASS (self)->state_change (self,
                                                  changed_states, changed_properties, changed_relations,
+                                                 self->updated_platform,
                                                  self->states, self->properties, self->relations);
   g_signal_emit (self, obj_signals[STATE_CHANGE], 0);
 
   self->updated_properties = 0;
   self->updated_relations = 0;
   self->updated_states = 0;
+  self->updated_platform = 0;
 }
 
 /*< private >
@@ -806,3 +811,10 @@ gtk_at_context_get_label (GtkATContext *self)
 
   return g_strdup ("widget");
 }
+
+void
+gtk_at_context_platform_changed (GtkATContext                *self,
+                                 GtkAccessiblePlatformChange  change)
+{
+  self->updated_platform |= change;
+}

gtk/gtkatcontextprivate.h

@@ -80,6 +80,11 @@ typedef enum {
   GTK_ACCESSIBLE_STATE_CHANGE_SELECTED = 1 << GTK_ACCESSIBLE_STATE_SELECTED
 } GtkAccessibleStateChange;
 
+typedef enum {
+  GTK_ACCESSIBLE_PLATFORM_CHANGE_FOCUSABLE = 1 << 0,
+  GTK_ACCESSIBLE_PLATFORM_CHANGE_FOCUSED   = 1 << 1,
+} GtkAccessiblePlatformChange;
+
 struct _GtkATContext
 {
   GObject parent_instance;
@@ -95,6 +100,7 @@ struct _GtkATContext
   GtkAccessibleStateChange updated_states;
   GtkAccessiblePropertyChange updated_properties;
   GtkAccessibleRelationChange updated_relations;
+  GtkAccessiblePlatformChange updated_platform;
 };
 
 struct _GtkATContextClass
@@ -105,6 +111,7 @@ struct _GtkATContextClass
                          GtkAccessibleStateChange     changed_states,
                          GtkAccessiblePropertyChange  changed_properties,
                          GtkAccessibleRelationChange  changed_relations,
+                         GtkAccessiblePlatformChange  changed_platform,
                          GtkAccessibleAttributeSet   *states,
                          GtkAccessibleAttributeSet   *properties,
                          GtkAccessibleAttributeSet   *relations);
@@ -138,6 +145,9 @@ GtkAccessibleValue *    gtk_at_context_get_accessible_relation  (GtkATContext
 
 char *                  gtk_at_context_get_label                (GtkATContext          *self);
 
+void                    gtk_at_context_platform_changed         (GtkATContext                *self,
+                                                                 GtkAccessiblePlatformChange  change);
+
 const char *    gtk_accessible_property_get_attribute_name      (GtkAccessibleProperty property);
 const char *    gtk_accessible_relation_get_attribute_name      (GtkAccessibleRelation relation);
 const char *    gtk_accessible_state_get_attribute_name         (GtkAccessibleState    state);

gtk/gtktestatcontext.c

@@ -23,6 +23,7 @@
 #include "gtktestatcontextprivate.h"
 
 #include "gtkatcontextprivate.h"
+#include "gtkaccessibleprivate.h"
 #include "gtkdebug.h"
 #include "gtkenums.h"
 #include "gtkprivate.h"
@@ -45,6 +46,7 @@ gtk_test_at_context_state_change (GtkATContext                *self,
                                   GtkAccessibleStateChange     changed_states,
                                   GtkAccessiblePropertyChange  changed_properties,
                                   GtkAccessibleRelationChange  changed_relations,
+                                  GtkAccessiblePlatformChange  changed_platform,
                                   GtkAccessibleAttributeSet   *states,
                                   GtkAccessibleAttributeSet   *properties,
                                   GtkAccessibleAttributeSet   *relations)