Obtain mouse click position relative to active window

Question

Having worked out how to obtain the mouse click position anywhere along the monitor boundaries using low level hooks I receive an X Y coordinate that will contain a value typically between x: -1680 to +1920 and y: 0 to 1200 in my pcs case. Easy enough!

Now the problem is that I now want to calculate the mouse position relative to a given window that I have so I use GetForegroundWindow() and GetWindowRect(HandleRef hWnd, out RECT lpRect) to obtain my active window coordinates.

Where I am stuck is I require the current active desktop (By active I mean which monitor the click occurred on) to calculate the coordinates of my mouse click relative to a window.

Unfortunately I have not been able to find an API call like GetActiveMonitor() or similar so hopefully someone can point me in the right direction?

Answer 1

[DllImport("user32.dll", SetLastError = true)]
 [return: MarshalAs(UnmanagedType.Bool)]
 static extern bool GetWindowRect(IntPtr hWnd, ref RECT lpRect);
 [StructLayout(LayoutKind.Sequential)]
 private struct RECT
 {
     public int Left;
     public int Top;
     public int Right;
     public int Bottom;
  }
Call it as:

  RECT rct = new RECT();
  GetWindowRect(hWnd, ref rct);

after get your mouse position like this

int mouserelativepositionX = mousePosition.X - rct.Left;
int mouserelativepositionY = mousePosition.Y - rct.Top;