examples: Update to bind settings inside UI definitions

And clean up the structure while we're at it.

examples/application9/exampleappprefs.c

@@ -7,10 +7,6 @@
 struct _ExampleAppPrefs
 {
   GtkDialog parent;
-
-  GSettings *settings;
-  GtkWidget *font;
-  GtkWidget *transition;
 };
 
 G_DEFINE_TYPE (ExampleAppPrefs, example_app_prefs, GTK_TYPE_DIALOG)
@@ -19,41 +15,20 @@ static void
 example_app_prefs_init (ExampleAppPrefs *prefs)
 {
   gtk_widget_init_template (GTK_WIDGET (prefs));
-  prefs->settings = g_settings_new ("org.gtk.exampleapp");
-
-  g_settings_bind (prefs->settings, "font",
-                   prefs->font, "font",
-                   G_SETTINGS_BIND_DEFAULT);
-  g_settings_bind (prefs->settings, "transition",
-                   prefs->transition, "active-id",
-                   G_SETTINGS_BIND_DEFAULT);
-}
-
-static void
-example_app_prefs_dispose (GObject *object)
-{
-  ExampleAppPrefs *prefs;
-
-  prefs = EXAMPLE_APP_PREFS (object);
-
-  g_clear_object (&prefs->settings);
-
-  G_OBJECT_CLASS (example_app_prefs_parent_class)->dispose (object);
 }
 
 static void
 example_app_prefs_class_init (ExampleAppPrefsClass *class)
 {
-  G_OBJECT_CLASS (class)->dispose = example_app_prefs_dispose;
-
   gtk_widget_class_set_template_from_resource (GTK_WIDGET_CLASS (class),
                                                "/org/gtk/exampleapp/prefs.ui");
-  gtk_widget_class_bind_template_child (GTK_WIDGET_CLASS (class), ExampleAppPrefs, font);
-  gtk_widget_class_bind_template_child (GTK_WIDGET_CLASS (class), ExampleAppPrefs, transition);
 }
 
 ExampleAppPrefs *
 example_app_prefs_new (ExampleAppWindow *win)
 {
-  return g_object_new (EXAMPLE_APP_PREFS_TYPE, "transient-for", win, "use-header-bar", TRUE, NULL);
+  return g_object_new (EXAMPLE_APP_PREFS_TYPE,
+                       "transient-for", win,
+                       "use-header-bar", TRUE,
+                       NULL);
 }

examples/application9/prefs.ui

@@ -28,6 +28,7 @@
             </child>
             <child>
               <object class="GtkFontButton" id="font">
+              <property name="font" bind-settings-schema="org.gtk.exampleapp" bind-settings-key="font"/>
                 <layout>
                   <property name="column">1</property>
                   <property name="row">0</property>
@@ -48,6 +49,7 @@
             </child>
             <child>
               <object class="GtkComboBoxText" id="transition">
+                <property name="active-id" bind-settings-schema="org.gtk.exampleapp" bind-settings-key="transition"/>
                 <items>
                   <item translatable="yes" id="none">None</item>
                   <item translatable="yes" id="crossfade">Fade</item>

gtk/gtkbuilder.c

@@ -65,6 +65,14 @@
  * using `dgettext()` in the domain specified. This can also be done by
  * calling [method@Gtk.Builder.set_translation_domain] on the builder.
  *
+ * The target toolkit version(s) are described by `<requires>` elements,
+ * the “lib” attribute specifies the widget library in question (currently
+ * the only supported value is “gtk”) and the “version” attribute specifies
+ * the target version in the form “`<major>`.`<minor>`”. `GtkBuilder` will
+ * error out if the version requirements are not met.
+ *
+ * ### Objects
+ *
  * Objects are described by `<object>` elements, which can contain
  * `<property>` elements to set properties, `<signal>` elements which
  * connect signals to handlers, and `<child>` elements, which describe
@@ -72,16 +80,10 @@
  * actions in an action group, or columns in a tree model). A `<child>`
  * element contains an `<object>` element which describes the child object.
  *
- * The target toolkit version(s) are described by `<requires>` elements,
- * the “lib” attribute specifies the widget library in question (currently
- * the only supported value is “gtk”) and the “version” attribute specifies
- * the target version in the form “`<major>`.`<minor>`”. `GtkBuilder` will
- * error out if the version requirements are not met.
- *
  * Typically, the specific kind of object represented by an `<object>`
  * element is specified by the “class” attribute. If the type has not
  * been loaded yet, GTK tries to find the `get_type()` function from the
- * class name by applying heuristics. This works in most cases, but if
+ * class name by applying heuristics; this works in most cases, but if
  * necessary, it is possible to specify the name of the `get_type()`
  * function explicitly with the "type-func" attribute.
  *
@@ -92,6 +94,8 @@
  * reserves ids starting and ending with `___` (three consecutive
  * underscores) for its own purposes.
  *
+ * ### Properties and values
+ *
  * Setting properties of objects is pretty straightforward with the
  * `<property>` element: the “name” attribute specifies the name of the
  * property, and the content of the element specifies the value.
@@ -125,12 +129,27 @@
  * exception to this rule is that an object has to be constructed before
  * it can be used as the value of a construct-only property.
  *
- * It is also possible to bind a property value to another object's
+ * ### Property bindings
+ *
+ * It is possible to bind a property value to another object's
  * property value using the attributes "bind-source" to specify the
  * source object of the binding, and optionally, "bind-property" and
  * "bind-flags" to specify the source property and source binding flags
  * respectively. Internally, `GtkBuilder` implements this using `GBinding`
- * objects. For more information see g_object_bind_property().
+ * objects. For more information see the documentation for
+ * [method@GObject.Object.bind_property].
+ *
+ * ### Settings bindings
+ *
+ * It is possible to bind a property value to a [class@Gio.Settings] key
+ * inside a schema, by using the attributes "bind-settings-schema" to
+ * define the schema, and "bind-settings-key" to define the key. If either
+ * attribute is set, the other is mandatory. Additionally, you can use
+ * the "bind-flags" attribute to specify the [enum@Gio.SettingsBindFlags]
+ * to be used by the binding. For more information see the documentation
+ * for [method@Gio.Settings.bind].
+ *
+ * ### Internal children
  *
  * Sometimes it is necessary to refer to widgets which have implicitly
  * been constructed by GTK as part of a composite widget, to set
@@ -146,7 +165,7 @@
  * The possible values for the “type” attribute are described in the
  * sections describing the widget-specific portions of UI definitions.
  *
- * # Signal handlers and function pointers
+ * ### Signal handlers and function pointers
  *
  * Signal handlers are set up with the `<signal>` element. The “name”
  * attribute specifies the name of the signal, and the “handler” attribute
@@ -161,9 +180,9 @@
  * the following details should be noted:
  *
  * When compiling applications for Windows, you must declare signal callbacks
- * with %G_MODULE_EXPORT, or they will not be put in the symbol table.
+ * with `G_MODULE_EXPORT`, or they will not be put in the symbol table.
  * On Linux and Unix, this is not necessary; applications should instead
- * be compiled with the -Wl,--export-dynamic `CFLAGS`, and linked against
+ * be compiled with the `-Wl,--export-dynamic` `CFLAGS`, and linked against
  * `gmodule-export-2.0`.
  *
  * # A GtkBuilder UI Definition
@@ -191,10 +210,10 @@
  * ```
  *
  * Beyond this general structure, several object classes define their
- * own XML DTD fragments for filling in the ANY placeholders in the DTD
- * above. Note that a custom element in a <child> element gets parsed by
+ * own XML DTD fragments for filling in the `ANY` placeholders in the DTD
+ * above. Note that a custom element in a `<child>` element gets parsed by
  * the custom tag handler of the parent object, while a custom element in
- * an <object> element gets parsed by the custom tag handler of the object.
+ * an `<object>` element gets parsed by the custom tag handler of the object.
  *
  * These XML fragments are explained in the documentation of the
  * respective objects.
@@ -719,6 +738,11 @@ gtk_builder_take_bindings (GtkBuilder *builder,
           BindingExpressionInfo *info = l->data;
           info->target = target;
         }
+      else if (common_info->tag_type == TAG_BINDING_SETTING)
+        {
+          BindingSettingsInfo *info = l->data;
+          info->target = target;
+        }
       else
         {
           g_assert_not_reached ();
@@ -1146,6 +1170,17 @@ gtk_builder_create_bindings (GtkBuilder  *builder,
 
           free_binding_expression_info (info);
         }
+      else if (common_info->tag_type == TAG_BINDING_SETTING)
+        {
+          BindingSettingsInfo *info = l->data;
+          GSettings *settings;
+
+          settings = g_settings_new (info->schema);
+          g_settings_bind (settings, info->key, info->target, info->target_pspec->name, info->flags);
+          g_object_unref (settings);
+
+          free_binding_settings_info (info);
+        }
       else
         g_assert_not_reached ();
     }

gtk/gtkbuilderparser.c

@@ -874,7 +874,8 @@ parse_property (ParserData   *data,
   const char *bind_source = NULL;
   const char *bind_property = NULL;
   const char *bind_flags_str = NULL;
-  GBindingFlags bind_flags = G_BINDING_DEFAULT;
+  const char *bind_schema = NULL;
+  const char *bind_key = NULL;
   gboolean translatable = FALSE;
   ObjectInfo *object_info;
   GParamSpec *pspec = NULL;
@@ -897,6 +898,8 @@ parse_property (ParserData   *data,
                                     G_MARKUP_COLLECT_STRING|G_MARKUP_COLLECT_OPTIONAL, "bind-source", &bind_source,
                                     G_MARKUP_COLLECT_STRING|G_MARKUP_COLLECT_OPTIONAL, "bind-property", &bind_property,
                                     G_MARKUP_COLLECT_STRING|G_MARKUP_COLLECT_OPTIONAL, "bind-flags", &bind_flags_str,
+                                    G_MARKUP_COLLECT_STRING|G_MARKUP_COLLECT_OPTIONAL, "bind-settings-schema", &bind_schema,
+                                    G_MARKUP_COLLECT_STRING|G_MARKUP_COLLECT_OPTIONAL, "bind-settings-key", &bind_key,
                                     G_MARKUP_COLLECT_INVALID))
     {
       _gtk_builder_prefix_error (data->builder, &data->ctx, error);
@@ -916,21 +919,59 @@ parse_property (ParserData   *data,
       return;
     }
 
-  if (bind_flags_str)
+  gtk_buildable_parse_context_get_position (&data->ctx, &line, &col);
+
+  if (bind_schema != NULL)
     {
-      if (!_gtk_builder_flags_from_string (G_TYPE_BINDING_FLAGS, NULL, bind_flags_str, &bind_flags, error))
+      GSettingsBindFlags bind_flags = G_SETTINGS_BIND_DEFAULT;
+
+      if (bind_flags_str)
         {
-          _gtk_builder_prefix_error (data->builder, &data->ctx, error);
+          if (!_gtk_builder_flags_from_string (G_TYPE_SETTINGS_BIND_FLAGS, NULL, bind_flags_str, &bind_flags, error))
+            {
+              _gtk_builder_prefix_error (data->builder, &data->ctx, error);
+              return;
+            }
+        }
+
+      if (bind_key != NULL)
+        {
+          BindingSettingsInfo *binfo;
+
+          binfo = g_slice_new0 (BindingSettingsInfo);
+          binfo->tag_type = TAG_BINDING_SETTING;
+          binfo->target = NULL;
+          binfo->target_pspec = pspec;
+          binfo->schema = g_strdup (bind_schema);
+          binfo->key = g_strdup (bind_key);
+          binfo->flags = bind_flags;
+          binfo->line = line;
+          binfo->col = col;
+
+          object_info->bindings = g_slist_prepend (object_info->bindings, binfo);
+        }
+      else
+        {
+          error_missing_attribute (data, element_name,
+                                   "bind-settings-key",
+                                   error);
           return;
         }
     }
-
-  gtk_buildable_parse_context_get_position (&data->ctx, &line, &col);
-
-  if (bind_source)
+  else if (bind_source != NULL)
     {
+      GBindingFlags bind_flags = G_BINDING_DEFAULT;
       BindingInfo *binfo;
 
+      if (bind_flags_str)
+        {
+          if (!_gtk_builder_flags_from_string (G_TYPE_BINDING_FLAGS, NULL, bind_flags_str, &bind_flags, error))
+            {
+              _gtk_builder_prefix_error (data->builder, &data->ctx, error);
+              return;
+            }
+        }
+
       binfo = g_slice_new0 (BindingInfo);
       binfo->tag_type = TAG_BINDING;
       binfo->target = NULL;
@@ -943,7 +984,14 @@ parse_property (ParserData   *data,
 
       object_info->bindings = g_slist_prepend (object_info->bindings, binfo);
     }
-  else if (bind_property)
+  else if (bind_key != NULL)
+    {
+      error_missing_attribute (data, element_name,
+                               "bind-settings-schema",
+                               error);
+      return;
+    }
+  else if (bind_property != NULL)
     {
       error_missing_attribute (data, element_name,
                                "bind-source",
@@ -956,7 +1004,7 @@ parse_property (ParserData   *data,
   info->pspec = pspec;
   info->text = g_string_new ("");
   info->translatable = translatable;
-  info->bound = bind_source != NULL;
+  info->bound = bind_source != NULL || bind_schema != NULL;
   info->context = g_strdup (context);
   info->line = line;
   info->col = col;
@@ -1563,6 +1611,14 @@ free_binding_expression_info (BindingExpressionInfo *info)
   g_slice_free (BindingExpressionInfo, info);
 }
 
+void
+free_binding_settings_info (BindingSettingsInfo *info)
+{
+  g_free (info->schema);
+  g_free (info->key);
+  g_slice_free (BindingSettingsInfo, info);
+}
+
 static void
 free_requires_info (RequiresInfo *info,
                     gpointer      user_data)

gtk/gtkbuilderprivate.h

@@ -27,6 +27,7 @@ enum {
   TAG_PROPERTY,
   TAG_BINDING,
   TAG_BINDING_EXPRESSION,
+  TAG_BINDING_SETTING,
   TAG_REQUIRES,
   TAG_OBJECT,
   TAG_CHILD,
@@ -141,6 +142,18 @@ typedef struct
   int col;
 } BindingExpressionInfo;
 
+typedef struct
+{
+  guint tag_type;
+  GObject *target;
+  GParamSpec *target_pspec;
+  char *schema;
+  char *key;
+  GSettingsBindFlags flags;
+  int line;
+  int col;
+} BindingSettingsInfo;
+
 typedef struct {
   guint    tag_type;
   char    *library;
@@ -228,6 +241,7 @@ void _free_signal_info (SignalInfo *info,
 void _free_binding_info (BindingInfo *info,
                          gpointer user_data);
 void free_binding_expression_info (BindingExpressionInfo *info);
+void free_binding_settings_info (BindingSettingsInfo *info);
 GtkExpression * expression_info_construct (GtkBuilder      *builder,
                                            ExpressionInfo  *info,
                                            GError         **error);