[gnome-games/wip/exalm/libhandy: 5/8] preferences-window: Use extra boxes for subpage

[Alexander Mikhaylenko <alexm src gnome org>]

commit 39f22245cb4ce9b1052176e1a4d5d6e1f0e11249
Author: Alexander Mikhaylenko <alexm gnome org>
Date:   Tue Feb 25 23:14:41 2020 +0500

    preferences-window: Use extra boxes for subpage
    
    Instead of modifying stacks on the fly, have placeholder boxes. This will
    avoid problems down the line.

 data/ui/preferences-window.ui  | 11 +++++++++++
 src/ui/preferences-window.vala | 16 ++++++++++------
 2 files changed, 21 insertions(+), 6 deletions(-)
---
diff --git a/data/ui/preferences-window.ui b/data/ui/preferences-window.ui
index 6bfefa1f..29068bca 100644
--- a/data/ui/preferences-window.ui
+++ b/data/ui/preferences-window.ui
@@ -96,6 +96,11 @@
                 </child>
               </object>
             </child>
+            <child>
+              <object class="GtkBox" id="titlebar_subpage_box">
+                <property name="visible">True</property>
+              </object>
+            </child>
           </object>
         </child>
       </object>
@@ -163,6 +168,12 @@
             </child>
           </object>
         </child>
+        <child>
+          <object class="GtkBox" id="content_subpage_box">
+            <property name="visible">True</property>
+            <property name="orientation">vertical</property>
+          </object>
+        </child>
       </object>
     </child>
   </template>
diff --git a/src/ui/preferences-window.vala b/src/ui/preferences-window.vala
index ccda289d..26b5b926 100644
--- a/src/ui/preferences-window.vala
+++ b/src/ui/preferences-window.vala
@@ -9,12 +9,16 @@ private class Games.PreferencesWindow : Gtk.Window {
        [GtkChild]
        private Hdy.Leaflet titlebar_box;
        [GtkChild]
+       private Gtk.Box titlebar_subpage_box;
+       [GtkChild]
        private Gtk.HeaderBar right_header_bar;
        [GtkChild]
        private Gtk.Stack main_stack;
        [GtkChild]
        private Hdy.Leaflet content_box;
        [GtkChild]
+       private Gtk.Box content_subpage_box;
+       [GtkChild]
        private PreferencesSidebar sidebar;
        [GtkChild]
        private Gtk.Stack stack;
@@ -42,15 +46,15 @@ private class Games.PreferencesWindow : Gtk.Window {
                        if (value != null) {
                                var header_bar = value.header_bar;
 
-                               main_stack.add (value);
-                               main_stack.visible_child = value;
+                               content_subpage_box.add (value);
+                               main_stack.visible_child = content_subpage_box;
 
                                selection_mode_binding = value.bind_property ("request-selection-mode",
                                                                              titlebar, "selection-mode",
                                                                              BindingFlags.SYNC_CREATE);
 
-                               titlebar_stack.add (header_bar);
-                               titlebar_stack.visible_child = header_bar;
+                               titlebar_subpage_box.add (header_bar);
+                               titlebar_stack.visible_child = titlebar_subpage_box;
 
                                content_box.navigate (Hdy.NavigationDirection.FORWARD);
                        }
@@ -96,8 +100,8 @@ private class Games.PreferencesWindow : Gtk.Window {
                if (main_stack.transition_running || previous_subpage == null)
                        return;
 
-               main_stack.remove (previous_subpage);
-               titlebar_stack.remove (previous_subpage.header_bar);
+               content_subpage_box.remove (previous_subpage);
+               titlebar_subpage_box.remove (previous_subpage.header_bar);
                previous_subpage = null;
        }