Create movable, transparent window.

I have my main window, which has a transparent background. What I want to do is to be able to drag it anywhere on the desktop - and be able to click on things that are outside of the window. If I make it full screen, it drags everywhere - but I can't click on anything underneath it. If I make it windowed, it only drags around inside the area of the window, and I still can't click on anything "underneath" it.

Here's my transparent window code:

Code (CSharp):

1. using System;
2. using System.Runtime.InteropServices;
3. using UnityEngine;
4.  
5. public class TransparentWindow : MonoBehaviour
6.   {
7.     [SerializeField]
8.     private Material m_Material;
9.  
10.     private struct MARGINS
11.       {
12.         public int cxLeftWidth;
13.         public int cxRightWidth;
14.         public int cyTopHeight;
15.         public int cyBottomHeight;
16.       }
17.  
18.     // Define function signatures to import from Windows APIs
19.  
20.     [DllImport("user32.dll")]
21.     private static extern IntPtr GetActiveWindow();
22.  
23.     [DllImport("user32.dll")]
24.     private static extern int SetWindowLong(IntPtr hWnd, int nIndex, uint dwNewLong);
25.  
26.     [DllImport("Dwmapi.dll")]
27.     private static extern uint DwmExtendFrameIntoClientArea(IntPtr hWnd, ref MARGINS margins);
28.  
29.     // Definitions of window styles
30.     const int GWL_STYLE = -16;
31.     const uint WS_POPUP = 0x80000000;
32.     const uint WS_VISIBLE = 0x10000000;
33.  
34.     void Start()
35.       {
36.         #if !UNITY_EDITOR
37.         var margins = new MARGINS() { cxLeftWidth = -1 };
38.  
39.         // Get a handle to the window
40.         var hwnd = GetActiveWindow();
41.  
42.         // Set properties of the window
43.         // See: https://msdn.microsoft.com/en-us/library/windows/desktop/ms633591%28v=vs.85%29.aspx
44.         SetWindowLong(hwnd, GWL_STYLE, WS_POPUP | WS_VISIBLE);
45.  
46.         // Extend the window into the client area
47.         See: https://msdn.microsoft.com/en-us/library/windows/desktop/aa969512%28v=vs.85%29.aspx
48.         DwmExtendFrameIntoClientArea(hwnd, ref margins);
49.         #endif
50.       }
51.  
52.     // Pass the output of the camera to the custom material
53.     // for chroma replacement
54.     void OnRenderImage(RenderTexture from, RenderTexture to)
55.       {
56.         Graphics.Blit(from, to, m_Material);
57.       }
58.   }

Can anyone help with this?? Thanks!