Search code examples
androidopengl-es

What is the right way to check if glClipControlEXT supported in an Android OpenGLES app?

How do I check if I can call glClipControlEXT in an Android OpenGLES app?

For example:

glClipControlEXT(GL_LOWER_LEFT_EXT, GL_ZERO_TO_ONE_EXT);

Should I enumerate all the extensions (as it done here)?

GLint no_of_extensions = 0;
glGetIntegerv(GL_NUM_EXTENSIONS, &no_of_extensions);

std::set<std::string> ogl_extensions;
for (int i = 0; i < no_of_extensions; ++i)
    ogl_extensions.insert((const char*)glGetStringi(GL_EXTENSIONS, i));

and find "EXT_clip_control"?

And how do I get the address of glClipControlEXT function?

EDIT1:

Tried to add the following to CMake:

add_definitions(-DGL_GLEXT_PROTOTYPES=1)
target_link_libraries(${PROJECT_NAME} PRIVATE GLESv2)

and was able to compile

glClipControlEXT(GL_LOWER_LEFT_EXT, GL_ZERO_TO_ONE_EXT);

in my app, but got linker error:

ld.lld: error: undefined symbol: glClipControlEXT

EDIT2:

Another alternative:

PFNGLCLIPCONTROLEXTPROC myClipControlEXT = (PFNGLCLIPCONTROLEXTPROC)eglGetProcAddress("glClipControlEXT");

myClipControlEXT(GL_LOWER_LEFT_EXT, GL_ZERO_TO_ONE_EXT);

//wglGetProcAddress(“glBlendEquation”)

GLenum tempClipOrigin, tempClipDepth;
glGetIntegerv(GL_CLIP_ORIGIN_EXT, (GLint *)&tempClipOrigin);
glGetIntegerv(GL_CLIP_DEPTH_MODE_EXT, (GLint *)&tempClipDepth);

qDebug() << "GL_CLIP_ORIGIN: " << tempClipOrigin << ", GL_CLIP_DEPTH_MODE: " << tempClipDepth;
Solution

  • Should I enumerate all the extensions ... and find EXT_clip_control?

    Yes

    How do I get the address of the glClipControlEXT function?

    eglGetProcAccess("glClipControlEXT");

    How do I check if I can call glClipControlEXT ...

    In general it doesn't seem that widely supported. https://opengles.gpuinfo.org/listextensions.php says its available on 17% of reported devices, although looking at the list most recent ones do.