GLproxy

GLproxy is a library for handling OpenGL function pointer management for you.

It hides the complexity of dlopen(), dlsym(), glXGetProcAddress(), eglGetProcAddress(), etc. from the app developer, with very little knowledge needed on their part. They get to read GL specs and write code using undecorated function names like glCompileShader().

Don't forget to check for your extensions or versions being present before you use them, just like before! We'll tell you what you forgot to check for instead of just segfaulting, though.

Features

• Automatically initializes as new OpenGL functions are used.
• Desktop OpenGL 4.4 core and compatibility context support.
• OpenGL ES 1/2/3 context support.
• Knows about function aliases so (e.g.) glBufferData() can be used with GL_ARB_vertex_buffer_object implementations, along with desktop OpenGL 1.5+ implementations.
• GLX, and WGL support.
• EGL support. EGL headers are included, so they're not necessary to build GLproxy with EGL support.
• Can be mixed with non-glproxy OpenGL usage.

Building (CMake)

CMake is now the recommended way to build glproxy. It supports building both shared and static libraries (by default only shared library is built). It also supports building and running tests, both for the static and the shared library.

Building with CMake should be as simple as running:

mkdir build
cd build
cmake -G "<my-generator>" ..
cmake --build .

Running tests for Win32 should be as simple as running: cmake --build . --target RUN_TESTS Running tests for Unix should be as simple as running: ctest

(run cmake -h see a list of possible generators). Then, to build the project, depending on the type of generator you use, e.g. for Unix type make, and for MSVC open the solution in Visual studio and build the solution.

• To build & test for 32 bit with MSVC, using the following command cmake -G "Visual Studio 14 2015" .. cmake --build . --config Release cmake --build . --target RUN_TESTS --config Release

  cmake --build . --config Debug cmake --build . --target RUN_TESTS --config Debug

• To build for 64 bit with MSVC add Win64 to the generator name, e.g. cmake -G "Visual Studio 14 2015 Win64" ..

• To rebuild the generated headers from the specs, add -DGLPROXY_REBUILD_FROM_SPECS=ON to the cmake invocation.

• To disable building shared libraries and building static libraries, add -DGLPROXY_BUILD_SHARED=OFF to the cmake invocation.

• To disable building tests, add -DGLPROXY_BUILD_TESTS=OFF to the cmake invocation.

• To link to the static Runtime Library with MSVC (rather than to the DLL), add -DGLPROXY_MSVC_USE_RUNTIME_LIBRARY_DLL=OFF to the cmake invocation.

Switching your Code to Use GLproxy

• NOTE: If you use the static version of GLproxy, you must build your project with "GLPROXY_STATIC_LIB" defined!

It should be as easy as replacing:

#include <GL/gl.h>
#include <GL/glx.h>
#include <GL/glext.h>
#include <EGL/egl.h>
#include <EGL/eglext.h>
#include <Windows.h> // for WGL

with:

#include <glproxy/gl.h>
#include <glproxy/glx.h>
#include <glproxy/egl.h>
#include <glproxy/wgl.h>

As long as glproxy's headers appear first, you should be ready to go. Additionally, some new helpers become available, so you don't have to write them:

int glproxy_gl_version() returns the GL version:

• 12 for GL 1.2
• 20 for GL 2.0
• 44 for GL 4.4

bool glproxy_has_gl_extension() returns whether a GL extension is available (GL_ARB_texture_buffer_object, for example).

Note that this is not terribly fast, so keep it out of your hot paths, ok?

Using OpenGL ES / EGL

Building GLproxy with OpenGL ES / EGL support is now built-in. However, to actually make use OpenGL ES and/or EGL on a computer, it's recommended (and in some platforms necessary) to use an OpenGL ES / EGL emulator. I recommend using PowerVR SDK, which is available for Linux, OS X and Windows. Download it and run the installer. In the installer, you don't have to check everything: Enough to check PowerVR Tools -> PVRVFrame and PowerVR SDK -> Native SDK. There's no need to add anything from PowerVR SDK to the include directories to build or use GLproxy, as it already includes all the necessary headers for using OpenGL ES / EGL. There's also no need to link with anything from PowerVR SDK to build or use GLproxy, as it loads the necessary libraries at run-time. However, when running your app, if want to use EGL / OpenGL ES, you'll have to add the directory that contains the right shared libraries (GLES_CM, GLESv2 and EGL) to your PATH environment variable. For instance, if you're on Windows, and used the default locations when installing PowerVR SDK, then add C:\Imagination\PowerVR_Graphics\PowerVR_Tools\PVRVFrame\Library\Windows_x86_64 to your PATH (for Windows 64 bit) or C:\Imagination\PowerVR_Graphics\PowerVR_Tools\PVRVFrame\Library\Windows_x86_32 (for Windows 32 bit). For other platforms it would be something similar. Of course, feel free to copy the shared libraries somewhere else.

Why not use GLEW?

GLEW has several issues:

• Doesn't know about aliases of functions (There are 5 providers of glPointParameterfv, for example, and you don't want to have to choose which one to call when they're all the same).
• Doesn't support Desktop OpenGL 3.2+ core contexts.
• Doesn't support OpenGL ES.
• Doesn't support EGL.
• Has a hard-to-maintain parser of extension specification text instead of using the old .spec file or the new .xml.
• Has significant startup time overhead when glewInit() autodetects the world.

The motivation for this project came out of previous use of libGLEW in piglit. Other GL dispatch code generation projects had similar failures. Ideally, piglit wants to be able to build a single binary for a test that can run on whatever context or window system it chooses, not based on link time choices.

We had to solve some of GLEW's problems for piglit and solving them meant replacing every single piece of GLEW, so we built piglit-dispatch from scratch. And since we wanted to reuse it in other GL-related projects, this is the result.

Multiple-Thread safe and multiple different context in the same thread

For main thread single opengl context, we have a global constructor to initiate a GLproxy context to respond to WGL/EGL/GLX/GL calles, and choose the system default one, for the GL context manager, the detecting order is:

• For Win32, the order is [WGL，EGL(Google ANGLE) ]
• For Linux, the order is [GLX, EGL]
• For MacOS, the order is [CGL(we provide no proxy for CGL), GLX]
• For iOS, there order is [EAGL(we provide no proxy for EAGL)]

For GL calls proxy, we first detecting the which type of GL context it is. then binding the following calls to that context permanantly. If we want to switch the GL context, using the following APIs to do that: glproxy_context_create glproxy_context_get glproxy_context_set glproxy_context_destroy