You can call SetCapture
to direct mouse clicks from anywhere on the desktop to your window. Call ReleaseCapture
after the click to return to normal.
If the user clicks on another application you will receive the click but the other application will also be activated, which you probably don't want. To avoid this, an alternative approach is to overlay the entire desktop with an always-on-top very nearly fully transparent window (a fully transparent window won't get clicks). Transparent windows are known as layered windows; use the WS_EX_LAYERED
extended style to create one.