Set mouse position not working c#

Question

I've been trying to write a small utility that will modify the boundaries of where my mouse can go on the whole screen. I've used the the global mouse hook library that I found here (I'm using version 1), and then pass the mouse position information from the event it generates to my own function (just a test to see it working for now).

internal void ProcessMouseEvent(System.Drawing.Point point)
{
    Cursor.Position = new Point(50,50);
}

When running it, the mouse does appear to flash to the specified point, but will instantly revert back to where it was before the change if it was a movement event. Only when it was done through a click event does it actually remain at the new position.

Answer 1

To limit where the mouse can go efficiently, you need to use cursor.clip. You can find its documentation here. It will do what you want much easier and is the recommended way.

Answer 2

The problem here is that the hook gives you a notification of the mouse message. But doesn't prevent it from being processed by the application that is going to actually process the notification. So it gets handled as normal and the mouse moves where it wants to go. What you need to do is actually block the message from being passed on, that requires returning a non-zero value from the hook callback.

The library does not permit you to tinker with the hook callback return value, it is going to require surgery. Beware it is buggy. I'll instead use this sample code. With this sample callback method:

private static IntPtr HookCallback(int nCode, IntPtr wParam, IntPtr lParam) {
    if (nCode >= 0 && MouseMessages.WM_MOUSEMOVE == (MouseMessages)wParam) {
        System.Windows.Forms.Cursor.Position = new Point(50, 50);
        return (IntPtr)1;   // Stop further processing!
    }
    return CallNextHookEx(_hookID, nCode, wParam, lParam);
}

And you'll see it is now solidly stuck. Use Alt+Tab, Alt+D, E to regain control.