Add a help overlay to bloatpad

This will let us explore the (non-)interaction between
help overlays and editing shortcuts.

examples/bp/Makefile.am

@@ -19,7 +19,8 @@ nodist_bloatpad_SOURCES = bloatpad-gresources.c
 
 resource_files = \
 	bloatpad.gresources.xml		\
-	gtk/menus.ui
+	gtk/menus.ui			\
+	gtk/help-overlay.ui
 
 bloatpad-gresources.c: $(resource_files)
 	$(AM_V_GEN) $(GLIB_COMPILE_RESOURCES) --target=$@ --sourcedir=$(srcdir) --generate-source $<

examples/bp/bloatpad.gresources.xml

@@ -3,5 +3,6 @@
 <gresources>
   <gresource prefix="/org/gtk/bloatpad">
     <file preprocess="xml-stripblanks">gtk/menus.ui</file>
+    <file preprocess="xml-stripblanks">gtk/help-overlay.ui</file>
   </gresource>
 </gresources>

examples/bp/gtk/help-overlay.ui

@@ -0,0 +1,47 @@
+<interface>
+  <!-- interface-requires gtk+ 3.17 -->
+  <object class="GtkShortcutsWindow" id="help_overlay">
+    <property name="modal">1</property>
+    <child>
+      <object class="GtkShortcutsSection">
+        <property name="visible">1</property>
+        <property name="section-name">shortcuts</property>
+        <property name="max-height">12</property>
+        <child>
+          <object class="GtkShortcutsGroup">
+            <property name="visible">1</property>
+            <property name="title">Shortcuts</property>
+            <child>
+              <object class="GtkShortcutsShortcut">
+                <property name="visible">1</property>
+                <property name="accelerator">&lt;Primary&gt;c</property>
+                <property name="title" translatable="yes">Copy</property>
+              </object>
+            </child>
+            <child>
+              <object class="GtkShortcutsShortcut">
+                <property name="visible">1</property>
+                <property name="accelerator">&lt;Primary&gt;p</property>
+                <property name="title" translatable="yes">Paste</property>
+              </object>
+            </child>
+            <child>
+              <object class="GtkShortcutsShortcut">
+                <property name="visible">1</property>
+                <property name="accelerator">F11</property>
+                <property name="title" translatable="yes">Fullscreen</property>
+              </object>
+            </child>
+            <child>
+              <object class="GtkShortcutsShortcut">
+                <property name="visible">1</property>
+                <property name="accelerator">&lt;Primary&gt;q</property>
+                <property name="title" translatable="yes">Quit</property>
+              </object>
+            </child>
+          </object>
+        </child>
+      </object>
+    </child>
+  </object>
+</interface>

examples/bp/gtk/menus.ui

@@ -60,6 +60,12 @@
           <attribute name='action'>app.edit-accels</attribute>
         </item>
       </section>
+      <section>
+        <item>
+          <attribute name='label' translatable='yes'>Shortcuts...</attribute>
+          <attribute name='action'>win.show-help-overlay</attribute>
+        </item>
+      </section>
     </submenu>
     <submenu>
       <attribute name='label' translatable='yes'>_View</attribute>