Apply fix from commit 14c5eaac0bf9505084f9fd0c64606af0845de856 to luainvaders:

    "create ShellRenderInterfaceOpenGL::SetViewport, instead of hardcoding
    the height of the screen for scissoring. anything that would overflow
    y with scrollbars would result in being cut off by a the difference between
    768 and the viewports current resolution. even the debugger was broken."

Samples/luainvaders/src/main.cpp

@@ -83,6 +83,7 @@ int main(int, char**)
 	// Rocket initialisation.
 	ShellRenderInterfaceOpenGL opengl_renderer;
 	Rocket::Core::SetRenderInterface(&opengl_renderer);
+	opengl_renderer.SetViewport(1024,768);
 
 	ShellSystemInterface system_interface;
 	Rocket::Core::SetSystemInterface(&system_interface);