Single source file function call interceptor for OpenGL. This project provides a basic skeleton for building more sophisticated OpenGL interceptors and detours.

The template project, opengl_proxy.cpp provides wrapper functions for the "classic OpenGL", AKA fixed function OpenGL, plus WGL on Windows and a few log utilities. As is stands, it can be used for basic interception of old OpenGL applications and GL-based games.

Currently only building for Windows. Tested on Windows 7, Visual Studio 2015.

The default DLL search strategy on Windows is:

• Application directory
• System directories

So we can take advantage of that and override system libraries, like opengl32.dll, by simply placing a new DLL with the same name and interface into the application directory.

GLProxy provides a template DLL project that defines a thin wrapper over OpenGL functions that in itself just forwards the calls to the actual OpenGL library. When compiled, it will output a proxy opengl32.dll that you can place in the install directory of an application and the app will reference it instead of the "real" OpenGL when run.

This opens the door for a lot of interesting things, from just logging every GL call made by an application, to saving draw calls to a file for later playback.

This project is just a base skeleton for anyone interested in writing their own interceptors, hence why it is small and entirely contained inside a single source file (opengl_proxy.cpp). It provides wrappers for most of the old fixed function OpenGL + WGL. The wrapper just forwards each call to the real OpenGL DLL, but it will also keep a global call count for each function and attempt to write a log file when the process terminates with the counts for each function.

For more robust uses and more mature projects, I suggest checking:

• GLIntercept
• APITrace
• RenderDoc

This project's source code is released under the MIT License.