According to what I've read on the web, this should work:
(hwnd is a top-level window with a GWL_STYLE of WS_THICKFRAME)
Code:
NSWindow* window = (NSWindow*)hwnd;
[window setAlphaValue:opacity];
[window setOpaque:NO];
However, instead of becoming transparent (i.e. showing other windows underneath) these parts fade to opaque white.
I have tried adding these lines to make the background transparent, but it doesn't appear to have any effect:
Code:
[window setWantsLayer:YES];
[window setBackgroundColor:[NSColor clearColor]];