[evince/wip/gpoo/gtk4-preparation-ev-sidebar: 3/4] shell: Add access to internal child to EvMessageArea

[Germán Poo-Caamaño <gpoo src gnome org>]

commit e523541b0649c72498f1fe7db08f9022db33fcc8
Author: Qiu Wenbo <qiuwenbo kylinos com cn>
Date:   Fri Mar 25 23:02:03 2022 -0300

    shell: Add access to internal child to EvMessageArea
    
    * Allow composite templates get access to internal main_box
      container.
    
    Co-authored-by: Germán Poo-Caamaño <gpoo gnome org>

 shell/ev-message-area.c | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)
---
diff --git a/shell/ev-message-area.c b/shell/ev-message-area.c
index dd43c70ef..d3c939593 100644
--- a/shell/ev-message-area.c
+++ b/shell/ev-message-area.c
@@ -47,8 +47,12 @@ static void ev_message_area_get_property (GObject      *object,
                                          guint         prop_id,
                                          GValue       *value,
                                          GParamSpec   *pspec);
+static void ev_message_area_buildable_iface_init (GtkBuildableIface *iface);
 
-G_DEFINE_TYPE_WITH_PRIVATE (EvMessageArea, ev_message_area, GTK_TYPE_INFO_BAR)
+G_DEFINE_TYPE_WITH_CODE (EvMessageArea, ev_message_area, GTK_TYPE_INFO_BAR,
+                         G_ADD_PRIVATE (EvMessageArea)
+                         G_IMPLEMENT_INTERFACE (GTK_TYPE_BUILDABLE,
+                                                ev_message_area_buildable_iface_init))
 
 #define GET_PRIVATE(o) ev_message_area_get_instance_private (o);
 
@@ -203,6 +207,29 @@ ev_message_area_get_property (GObject     *object,
        }
 }
 
+static GtkBuildableIface *parent_buildable_iface;
+
+static GObject *
+ev_message_area_buildable_get_internal_child (GtkBuildable *buildable,
+                             GtkBuilder   *builder,
+                             const char   *childname)
+{
+        EvMessageArea *area = EV_MESSAGE_AREA (buildable);
+
+        if (g_strcmp0 (childname, "main_box") == 0)
+                return G_OBJECT (_ev_message_area_get_main_box (area));
+
+        return parent_buildable_iface->get_internal_child (buildable, builder, childname);
+}
+
+static void
+ev_message_area_buildable_iface_init (GtkBuildableIface *iface)
+{
+        parent_buildable_iface = g_type_interface_peek_parent (iface);
+
+        iface->get_internal_child = ev_message_area_buildable_get_internal_child;
+}
+
 void
 _ev_message_area_add_buttons_valist (EvMessageArea *area,
                                     const gchar   *first_button_text,