Hello, I am using a code sample to connect to a webcam, and don't really understand the meaning of the variables passed to the SendMessage method.

SendMessage(DeviceHandle, WM_CAP_SET_SCALE, -1, 0)

SendMessage(DeviceHandle, WM_CAP_SET_PREVIEW, -1, 0)

What does the -1 mean? To scale/preview or not to scale/preview? I'd prefer that zero/one would be used, zero meaning false, and have no idea what the -1 means.

SendMessage(DeviceHandle, WM_CAP_EDIT_COPY, 0, 0);

What does the zero mean in this case? Or does this message is simply void and the zero has no meaning, similar to the last zero argument?

Btw, what DOES the last zero argument mean?

Thank you very much in advance :)