Shift and ctrl prevent events from happening? (Winapi)

Question

My application redraws the screen every time the mouse moves. I have not at all handled WM_KEYDOWN and I noticed that when I press shift or ctrl, it does not redraw on mouse mouse, nor does it seem to really do anything else. What could cause such a thing? If I press any other key like Z or X it does exactly what it should.

Thanks

Answer 1

No, they certainly don't prevent events from happening. But they seem to be preventing your code from recognizing them.

There's a handful of flags included with the event code, and they represent pressed keys/buttons. You'll probably notice the same effect with Alt or a pressed mouse button. My guess would be that you're comparing a combination of event code and keyboard status with a combination of event code and 0, and that comparison is failing when those shift keys are pushed.