c# - Hook/Overlay a DirectX game?

Question

Can anyone tell me how to hook/overlay a DirectX game in C#?

I've tried getting a fullscreen C# window to overlap a game, however it wont. After researching a little, I found out that I need to hook the game and then display the C# window.

Can anyone explain how I would do this? Would I be able to display a C# form over a DirectX game?

Answer 1

You can try my example on hooking the Direct3D 9 API using C#. This utilizes EasyHook an open source .NET assembly that allows you to install hooks from managed code into unmanaged functions.

SlimDX is also used - this is an open source managed wrapper around the Direct3D libraries.

The tricky part of the hooking is determining the addresses of a COM objects' virtual functions. This is done in the above example using a small C++ helper DLL that finds the addresses from the VTable. [Update: there is a comment posted that show's how to get the function pointers from the VTable in C# also - given a IntPtr to the com object]

The example hooks the EndScene method of an IDirect3DDevice9, which is also where you would want to draw any overlays. As to displaying a form in the overlay I'm not so sure that will be so easy - I mean you can render the image easily enough, but you will have to capture inputs and manually respond/pass-thru the events to the form in question appropriately. Good luck!