Is rendering on overlays generaly better than rendering on ordinary windows, and how can I create an overlay window in Win32?
Thanks in advance.
First you’ll need a graphics system which supports OpenGL overlay planes. MS GDI generic OpenGL implementation doesn’t, so you’ll need a workstation class graphics adapter.
Still interested?
Overlays are normally implemented as color_index and only used for things like rubber bands and wireframe representations of underlying graphics. On some implementations they are mutually exclusive with the destination alpha channel.
You’ll have to enumerate the pixelformats and find one which allows overlays and create an additional rendercontext on a layerplane.
Check the PIXELFORMATDESCRIPTOR bReserved field and LAYERPLANEDESCRIPTOR docs.
But even if it’s convenient, there is not much you can do with it, you couldn’t do with some other tricks like buffer_regions.