[tepl] Stack: add bind_setting()

[Sébastien Wilmet <swilmet src gnome org>]

commit 16a92be2d0b4cb18a17b91d15f8678fd658ee294
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Mon Apr 20 17:02:06 2020 +0200

    Stack: add bind_setting()

 docs/reference/tepl-sections.txt |  1 +
 tepl/tepl-stack.c                | 66 ++++++++++++++++++++++++++++++++++++++++
 tepl/tepl-stack.h                |  4 +++
 3 files changed, 71 insertions(+)
---
diff --git a/docs/reference/tepl-sections.txt b/docs/reference/tepl-sections.txt
index b094fa2..a31b2b2 100644
--- a/docs/reference/tepl-sections.txt
+++ b/docs/reference/tepl-sections.txt
@@ -321,6 +321,7 @@ tepl_metadata_manager_get_type
 <SECTION>
 <FILE>stack</FILE>
 tepl_stack_add_component
+tepl_stack_bind_setting
 </SECTION>
 
 <SECTION>
diff --git a/tepl/tepl-stack.c b/tepl/tepl-stack.c
index 729c529..92e60c6 100644
--- a/tepl/tepl-stack.c
+++ b/tepl/tepl-stack.c
@@ -56,3 +56,69 @@ tepl_stack_add_component (GtkStack    *stack,
                                 "icon-name", icon_name,
                                 NULL);
 }
+
+static gboolean
+bind_get_mapping_cb (GValue   *to_property_value,
+                    GVariant *from_setting_variant,
+                    gpointer  user_data)
+{
+       GtkStack *stack = GTK_STACK (user_data);
+       const gchar *child_name;
+       GtkWidget *child_widget;
+
+       child_name = g_variant_get_string (from_setting_variant, NULL);
+       child_widget = gtk_stack_get_child_by_name (stack, child_name);
+
+       /* If child_widget is NULL, do nothing, and do not print an error. It
+        * can happen if it's an old GSettings value and the child in the
+        * GtkStack no longer exists after an upgrade of the application.
+        */
+
+       if (child_widget != NULL)
+       {
+               g_value_set_string (to_property_value, child_name);
+       }
+
+       return TRUE;
+}
+
+/**
+ * tepl_stack_bind_setting:
+ * @stack: a #GtkStack.
+ * @settings: a #GSettings object.
+ * @setting_key: the #GSettings key of type string.
+ *
+ * Binds the provided #GSettings key with the #GtkStack:visible-child-name
+ * property of @stack.
+ *
+ * This function must be called when all #GtkWidget children have been added to
+ * @stack, to initially restore the state from #GSettings and then to update the
+ * #GSettings key when the visible child changes.
+ *
+ * Since: 5.0
+ */
+void
+tepl_stack_bind_setting (GtkStack    *stack,
+                        GSettings   *settings,
+                        const gchar *setting_key)
+{
+       g_return_if_fail (GTK_IS_STACK (stack));
+       g_return_if_fail (G_IS_SETTINGS (settings));
+       g_return_if_fail (setting_key != NULL);
+
+       /* G_SETTINGS_BIND_GET_NO_CHANGES is used because an application can
+        * have several windows with the same GtkStack/panel class, bound to the
+        * same GSettings key. But the visible child widget can be different on
+        * each window. On application exit, the GSettings key is set for the
+        * last closed window.
+        */
+       g_settings_bind_with_mapping (settings, setting_key,
+                                     stack, "visible-child-name",
+                                     G_SETTINGS_BIND_SET |
+                                     G_SETTINGS_BIND_GET |
+                                     G_SETTINGS_BIND_GET_NO_CHANGES |
+                                     G_SETTINGS_BIND_NO_SENSITIVITY,
+                                     bind_get_mapping_cb,
+                                     NULL,
+                                     stack, NULL);
+}
diff --git a/tepl/tepl-stack.h b/tepl/tepl-stack.h
index 74e82b7..0c4b23c 100644
--- a/tepl/tepl-stack.h
+++ b/tepl/tepl-stack.h
@@ -34,6 +34,10 @@ void tepl_stack_add_component        (GtkStack    *stack,
                                         const gchar *title,
                                         const gchar *icon_name);
 
+void   tepl_stack_bind_setting         (GtkStack    *stack,
+                                        GSettings   *settings,
+                                        const gchar *setting_key);
+
 G_END_DECLS
 
 #endif /* TEPL_STACK_H */