How do I determine if a window is off-screen?

Question

In Windows XP and above, given a window handle (HWND), how can I tell if the window position and size leaves the window irretrievably off screen? For example, if the title

Answer 1

You can use MonitorFromRect or MonitorFromPoint to check if window's top left point or bottom right point isn't contained within any display monitor (off screen).

POINT p;
p.x = x;
p.y = y;
HMONITOR hMon = MonitorFromPoint(p, MONITOR_DEFAULTTONULL);
if (hMon == NULL) {
    // point is off screen
}