My WndProc isn't seeing mouse-up notifications when I click with a modifier key (shift or control) pressed. I see them without the modifier key, and I see mouse-down notifications with the modifier keys.

I'm using the Windows Forms NativeWindow wrapper to get Windows messages from the WndProc() method.

I've tried tracking the notifications I do get, and I the only clue I see is WM_CAPTURECHANGED. I've tried calling SetCapture when I receive the WM_LBUTTONDOWN message, but it doesn't help.

Without modifier (skipping paint, timer and NCHITTEST messages):

WM_LBUTTONDOWN
WM_SETCURSOR
WM_MOUSEMOVE
WM_SETCURSOR
WM_LBUTTONUP

With modifier (skipping paint, timer and NCHITTEST messages):

WM_KEYDOWN
WM_PARENTNOTIFY
WM_MOUSEACTIVATE
WM_MOUSEACTIVATE
WM_SETCURSOR
WM_LBUTTONDOWN
WM_SETCURSOR (repeats)
WM_KEYDOWN (repeats)
WM_KEYUP

If I hold the mouse button down for a long time, I can usually get a WM_LBUTTONUP notification, but it should be possible to make it more responsive..

What am I missing?

Thanks.