map MenuToggleButton to GtkToggleButton with a custom menu property

we don't have non-menu ToggleButtons yet, so thats not done here.

since we first started with GtkPushButton:menu_attrib to indicate
menubuttons gtk has grown menu buttons, but they don't have the
idea of a gtktogglemenu button, so this attribute still has a role
to play I guess

Change-Id: Iebfe5ccf996e22784cf9aaf2bcf367eed79ae686

sfx2/uiconfig/ui/startcenter.ui

@@ -171,7 +171,7 @@
                   </packing>
                 </child>
                 <child>
-                  <object class="GtkButton" id="open_recent:clearmenu">
+                  <object class="GtkToggleButton" id="open_recent:clearmenu">
                     <property name="label" translatable="yes">_Recent Files</property>
                     <property name="visible">True</property>
                     <property name="can_focus">True</property>
@@ -190,7 +190,7 @@
                   </packing>
                 </child>
                 <child>
-                  <object class="GtkButton" id="templates_all:filtermenu">
+                  <object class="GtkToggleButton" id="templates_all:filtermenu">
                     <property name="label" translatable="yes">T_emplates</property>
                     <property name="visible">True</property>
                     <property name="can_focus">True</property>

vcl/source/window/builder.cxx

@@ -942,6 +942,22 @@ namespace
         return xWindow;
     }
 
+    VclPtr<Button> extractStockAndBuildMenuToggleButton(vcl::Window *pParent, VclBuilder::stringmap &rMap)
+    {
+        WinBits nBits = WB_CLIPCHILDREN|WB_CENTER|WB_VCENTER|WB_3DLOOK;
+
+        nBits |= extractRelief(rMap);
+
+        VclPtr<Button> xWindow = VclPtr<MenuToggleButton>::Create(pParent, nBits);
+
+        if (extractStock(rMap))
+        {
+            xWindow->SetText(getStockText(extractLabel(rMap)));
+        }
+
+        return xWindow;
+    }
+
     OString extractUnit(const OString& sPattern)
     {
         OString sUnit(sPattern);
@@ -1370,6 +1386,17 @@ VclPtr<vcl::Window> VclBuilder::makeObject(vcl::Window *pParent, const OString &
         setupFromActionName(xButton, rMap, m_xFrame);
         xWindow = xButton;
     }
+    else if (name == "GtkToggleButton")
+    {
+        VclPtr<Button> xButton;
+        OString sMenu = extractCustomProperty(rMap);
+        assert(sMenu.getLength() && "not implemented yet");
+        xButton = extractStockAndBuildMenuToggleButton(pParent, rMap);
+        m_pParserState->m_aButtonMenuMaps.push_back(ButtonMenuMap(id, sMenu));
+        xButton->SetImageAlign(ImageAlign::Left); //default to left
+        setupFromActionName(xButton, rMap, m_xFrame);
+        xWindow = xButton;
+    }
     else if (name == "GtkRadioButton")
     {
         extractGroup(id, rMap);