In Emscripten glDrawBuffers is just glDrawBuffers. To query if that
extension is supported, look for the string "WEBGL_draw_buffers" in
glGetString(GL_EXTENSIONS);, e.g.
if (strstr(glGetString(GL_EXTENSIONS), "WEBGL_draw_buffers"))
{
printf("WEBGL_draw_buffers is supported!\n");
glDrawBuffers(...); // Now safe to call WEBGL_draw_buffers since we know
it is supported.
}
2014-08-24 20:34 GMT+03:00 Robert Goulet <[email protected]>:
> Yes perhaps you are right. If I use glDrawBuffers directly, it seems to
> work (no GL error reported), however glDrawBuffers is not supported by
> WebGL 1.0 specs. To use it, one must query for the extension
> WEBGL_draw_buffers.
>
> So then I am wondering, what does Emscripten glDrawBuffers map to?
>
> On Sunday, August 24, 2014 1:22:14 PM UTC-4, jj wrote:
>
>> Oh wait, actually that sounds odd like Alon mentions: Are you calling
>> getProcAddress with the name of an extension? That's unexpected, it's only
>> supposed to be used for function names that an extension supports. Does
>> glfwGetProcAddress("glDrawBuffers") work?
>>
>>
>> 2014-08-24 20:07 GMT+03:00 Alon Zakai <[email protected]>:
>>
>>> Hmm, looks like we don't support any extensions in our getProcAddress
>>> code. It just supports functions. Should it support extensions? I'm not
>>> sure which docs to read regarding that.
>>>
>>> - Alon
>>>
>>>
>>>
>>> On Sun, Aug 24, 2014 at 9:46 AM, Jukka Jylänki <[email protected]> wrote:
>>>
>>>> In Emscripten you have all the GL functions for core spec and
>>>> extensions available already statically at compile-time without having to
>>>> obtain function pointers. Calling the functions without obtaining pointers
>>>> is preferred, since it gives better performance and is generally also
>>>> simpler.
>>>>
>>>> If you still want to call the function by querying the pointers e.g. in
>>>> order to have a symmetric code path for both native and Emscripten, you
>>>> should be able to. Perhaps we are missing support for that
>>>> function/extension in glfwGetProcAddress? Try checking the
>>>> src/library_gl.js and src/library_glfw.js on how they go through the route
>>>> to obtain the function pointers to see what might be off there.
>>>>
>>>>
>>>> 2014-08-24 19:39 GMT+03:00 Robert Goulet <[email protected]>:
>>>>
>>>> Hello,
>>>>>
>>>>> I am trying to get a WebGL extension, namely WEBGL_draw_buffers,
>>>>> using glfwGetProcAddress and it always return nullptr. When I list
>>>>> all the available extensions of my browser I clearly see that
>>>>> WEBGL_draw_buffers is listed, and I am even able to run a demo on a
>>>>> web page that make use of it. So why glfwGetProcAddress always
>>>>> returns nullptr when used with Emscripten? Is this supposed to work?
>>>>>
>>>>> Chrome JS console output this error:
>>>>> bad name in getProcAddress: WEBGL_draw_buffers | WEBGL_draw_buffers
>>>>>
>>>>> Also I am not sure if this is needed, but I made sure WebGL draft
>>>>> extensions are enabled in Chrome.
>>>>>
>>>>> Or maybe glDrawBuffers is already mapped to WEBGL_draw_buffers when
>>>>> used in Emscripten? Can anyone confirm/deny this?
>>>>>
>>>>> Thank you!
>>>>>
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