I know it's been a couple of months since you folks had this discussion, but with the help of a terrific Unity admin, I have the answer to 100% window transparency with 100% visible game objects! :) LWA_COLORKEY is a red herring... For all the details, and an example, have a look at this thread on the Unity forums: http://forum.unity3d.com/threads/solved-windows-transparent-window-with-opaque-contents-lwa_colorkey.323057/

Thanks so much for letting me know! I got it working with click-through and always on top

using System; using System.Runtime.InteropServices; using UnityEngine;

public class TransparentWindow : MonoBehaviour { [SerializeField] private Material m_Material;

 private struct MARGINS
 {
     public int cxLeftWidth;
     public int cxRightWidth;
     public int cyTopHeight;
     public int cyBottomHeight;
 }

 [DllImport("user32.dll")]
 private static extern IntPtr GetActiveWindow();

 [DllImport("user32.dll")]
 private static extern int SetWindowLong(IntPtr hWnd, int nIndex, uint dwNewLong);

 [DllImport("user32.dll")]
 static extern bool ShowWindowAsync(IntPtr hWnd, int nCmdShow);

 [DllImport("user32.dll", EntryPoint = "SetLayeredWindowAttributes")]
 static extern int SetLayeredWindowAttributes(IntPtr hwnd, int crKey, byte bAlpha, int dwFlags);

 [DllImport("user32.dll", EntryPoint = "SetWindowPos")]
 private static extern int SetWindowPos(IntPtr hwnd, int hwndInsertAfter, int x, int y, int cx, int cy, int uFlags);

 [DllImport("Dwmapi.dll")]
 private static extern uint DwmExtendFrameIntoClientArea(IntPtr hWnd, ref MARGINS margins);

 const int GWL_STYLE = -16;
 const uint WS_POPUP = 0x80000000;
 const uint WS_VISIBLE = 0x10000000;
 const int HWND_TOPMOST = -1;

 void Start()
 {
     #if !UNITY_EDITOR   // You really don't want to enable this in the editor..
     
     int fWidth = Screen.width;
     int fHeight = Screen.height;
     var margins = new MARGINS() { cxLeftWidth = -1 };
     var hwnd = GetActiveWindow();

     SetWindowLong(hwnd, GWL_STYLE, WS_POPUP | WS_VISIBLE);

     // Transparent windows with click through
     SetWindowLong(hwnd, -20, 524288 | 32);//GWL_EXSTYLE=-20; WS_EX_LAYERED=524288=&h80000, WS_EX_TRANSPARENT=32=0x00000020L
     SetLayeredWindowAttributes(hwnd, 0, 255, 2);// Transparency=51=20%, LWA_ALPHA=2
     SetWindowPos(hwnd, HWND_TOPMOST, 0, 0, fWidth, fHeight, 32 | 64); //SWP_FRAMECHANGED = 0x0020 (32); //SWP_SHOWWINDOW = 0x0040 (64)
     DwmExtendFrameIntoClientArea(hwnd, ref margins);

endif

}

 void OnRenderImage(RenderTexture from, RenderTexture to)
 {
     Graphics.Blit(from, to, m_Material);
 }

}

Hey all!

Any idea how to this on Mac OS?

I typed a big answer about how to do what you're trying to do, you want your PC and/or apps to run and be rendered in a running Unity build. Unfortunately, this 'help site' decided my post was an attack and erased what I wrote. So, I'm not going to type it all again, but it is easy to do (if you know what you're doing). The answers on this page seem to have nothing to do with your question, they are mostly for altering windows. You had it right when you mentioned Remote Desktop, basically. That is the way Remote Desktop works, it takes the video-memory stream, translates it to a mobile-friendly version, then feeds it over the internet to your device/PC. That's the simple part, ANY data going through your computer can be read, copied or altered. Graphics, video, sound, text, data from programs, input from the keyboard, etc. Unity would be even faster than Remote Desktop because it wouldn't have to send the data online, assuming Unity was running on the device you wanted to 'stream'. Also, instead of streaming to Unity or emulating an app inside Unity, sometimes it might just be easier to write a basic C#/java web-browser that runs inside Unity, or a 'fake Desktop' that interfaces with Windows/Android.