Add option for showing offline user guide

Navigating directly to the online website is useful, but having the option to
view the locally-installed version is still valuable for development and
perhaps for some users who cannot or do not wish to rely on online resources.

There are now two entries in the Help menu: "User Guide (Online)" and "User
Guide (Local)" to cover both of these options.

install/menu.xml

@@ -326,6 +326,7 @@
 
 	<subMenu name="help" caption="&amp;Help">
 		<menuItem name="about" caption="&amp;About" command="About" />
-		<menuItem name="userGuide" caption="&amp;User Guide" command="ShowUserGuide" />
+		<menuItem name="userGuide" caption="&amp;User Guide (Online)" command="ShowUserGuide" />
+		<menuItem name="userGuide" caption="&amp;User Guide (Local)" command="ShowOfflineUserGuide" />
 	</subMenu>
 </menu>

radiant/ui/Documentation.cpp

@@ -2,6 +2,7 @@
 #include "registry/registry.h"
 
 #include <wx/utils.h>
+#include "imodule.h"
 
 namespace ui
 {
@@ -16,4 +17,10 @@ void Documentation::showUserGuide(const cmd::ArgumentList&)
     wxLaunchDefaultBrowser(registry::getValue<std::string>(RKEY_USER_GUIDE_URL));
 }
 
+void Documentation::showOfflineUserGuide(const cmd::ArgumentList&)
+{
+    const IApplicationContext& ctx = module::GlobalModuleRegistry().getApplicationContext();
+    wxLaunchDefaultBrowser(ctx.getHTMLPath() + "manual.html");
+}
+
 }

radiant/ui/Documentation.h

@@ -10,8 +10,11 @@ class Documentation
 {
 public:
 
-    /// Show the user guide
+    /// Show the user guide online
     static void showUserGuide(const cmd::ArgumentList&);
+
+    /// Show the locally-installed user guide
+    static void showOfflineUserGuide(const cmd::ArgumentList&);
 };
 
 }

radiant/ui/UserInterfaceModule.cpp

@@ -392,6 +392,7 @@ void UserInterfaceModule::registerUICommands()
 	GlobalCommandSystem().addCommand("ShowCommandList", CommandList::ShowDialog);
 	GlobalCommandSystem().addCommand("About", AboutDialog::showDialog);
 	GlobalCommandSystem().addCommand("ShowUserGuide", Documentation::showUserGuide);
+	GlobalCommandSystem().addCommand("ShowOfflineUserGuide", Documentation::showOfflineUserGuide);
 	GlobalCommandSystem().addCommand("ExportSelectedAsModelDialog", ExportAsModelDialog::ShowDialog);
 
 	GlobalCommandSystem().addCommand("EntityClassTree", EClassTree::ShowDialog);