External window bugs on Windows

[Robin]

Originally Posted by Skyld

The external GUI windows on Windows are framebuffer, as opposed to OpenGL/DirectX, which would explain why GUI alpha doesn't work. Wondering whether this is also the reason for the polygon problem.

It will definitely be the reason if he is using opengl/directx polygon functions to draw them, however there is a way to get this working with directx (as it has support for the windows GDI) by first creating an offscreen buffer, rendering to that and then rendering back.