vsync on secondary display

Hi all,

I’m an openGL beginner and I came across a problem. Our application should show some video (simple openGL rendering) on secondary monitor (projector) and has to be vsync-ed.

I’m using win7, with desktop composition (aero) disabled, GPU AMD HD7750 (newest openGL supported), two monitors (DVI, HDMI) at approx. 60Hz, although the frequencies must be arbitrary (finally the secondary display will be a projector at 24/25Hz).

If I use wglSwapIntervalEXT(1), the animation is nice on the primary monitor (DVI), but if I move to secondary one (HDMI), there is an apparent tearing. It looks to be vsync-ed to the primary monitor, as the tearing is steady and moves slowly horizontally (a slight difference in refresh rates).
I tried to change the display order (swapped monitor desktop position, made the secondary one a “main monitor” etc) as recommended somewhere, but the behavior is still the same (and even if it works somehow, it is not desired behavior).

I tried to create the windows via GLUT and also via the win32 api (just thought maybe the OS cannot deduce which display is the window on), but result is still same.

I expect this feature should be feasible, because when aero is enabled, windows does it well (except full-screen where it seems that the implicit vsync is disabled).

Does somebody have any hints?