# How do I configure the OpenGL Context on macOS to not be "forward-compatible"?
**URL:** https://discourse.gstreamer.org/t/how-do-i-configure-the-opengl-context-on-macos-to-not-be-forward-compatible/1108
**Category:** Application Development
**Tags:** macos
**Created:** [March 2, 2024, 7:12am UTC](https://discourse.gstreamer.org/t/how-do-i-configure-the-opengl-context-on-macos-to-not-be-forward-compatible/1108 "2024-03-02T07:12:21Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@bes](https://discourse.gstreamer.org/u/bes)
#### Post date: [March 2, 2024, 7:12am UTC](https://discourse.gstreamer.org/t/how-do-i-configure-the-opengl-context-on-macos-to-not-be-forward-compatible/1108/1 "2024-03-02T07:12:21Z")
I would like to get an OpenGL context from GStreamer on macOS that is not “forward-compatible”, i.e. doesn’t remove deprecated OpenGL features.
I am using this command to try out my custom Rust Element:
```shell
GST_GL_CONFIG="gst-gl-context-config,forward_compatible=0" GST_PLUGIN_PATH=$(pwd)/target/debug gst-launch-1.0 gltestsrc ! gstreamertest ! autovideosink
```
But from what I can tell, the context I receive still returns 0 for some configuration values, specifically (code from the `wgpu` crate):
```rust
// ...
max_inter_stage_shader_components: unsafe {
gl.get_parameter_i32(glow::MAX_VARYING_COMPONENTS)
} as u32,
// ...
```
returns 0 for `MAX_VARYING_COMPONENTS`, which from what I understand would happen if I get a forward-compatible context, since deprecated APIs are removed from a forward-compatible context, even though they are not removed from the spec or implementation.
I have also tried the following
- `GST_GL_CONFIG="gst-gl-context-config,forward_compatible=0"`
- `GST_GL_CONFIG="gst-gl-context-config,forward_compatible=false"`
- `GST_GL_CONFIG="gst-gl-context-config,forward_compatible=FALSE"`
- `GST_GL_CONFIG="gst-gl-context-config,forward_compatible=no"`
None of which worked, either.
Maybe there is some other way to negotiate a forward-compatible context? Any help would be appreciated.
EDIT: Wrote `forward_compatible=1/true/yes` but was supposed to write `forward_compatible=0/false/no`.
---
### Author:  [@bes](https://discourse.gstreamer.org/u/bes)
#### Post date: [March 2, 2024, 11:03am UTC](https://discourse.gstreamer.org/t/how-do-i-configure-the-opengl-context-on-macos-to-not-be-forward-compatible/1108/2 "2024-03-02T11:03:44Z")
# OpenGL Profile
I have been researching some more, and I think being able to select a `compatibility` profile instead of a `core` profile would work as well, I think.
I used this snippet
```rust
let supports_compat = c.supports_glsl_profile_version(GLSLVersion::_410, GLSLProfile::COMPATIBILITY);
let supports_core = c.supports_glsl_profile_version(GLSLVersion::_410, GLSLProfile::CORE);
let supports_es = c.supports_glsl_profile_version(GLSLVersion::_410, GLSLProfile::ES);
println!("Supports compat: {supports_compat}, core: {supports_core}, es: {supports_es}");
```
Which prints
```auto
Supports compat: false, core: true, es: false
```
So either using a `compatibility` profile or setting `forward-compatibility` to false would work, I think.
# GStreamer code
I am trying to get a sense of what’s going on in `subprojects/gst-plugins-base/gst-libs/gst/gl/cocoa/gstglcontext_cocoa.m`, but I can’t find anything related to `forward-compatibility` in the entire codebase.
# GST\_GL\_API environment variable
I also tried using `GST_GL_API="opengl"`, but that gives me an OpenGL 2.1 context, which can’t be used by `wgpu` (requires at least OpenGL 3.3 or GLES 3.0).
Using `GST_GL_API="opengl3"` gives a OpenGL 4.1 context with the core profile on macOS.
---
### Author:  [@ystreet00](https://discourse.gstreamer.org/u/ystreet00)
#### Post date: [March 2, 2024, 11:28am UTC](https://discourse.gstreamer.org/t/how-do-i-configure-the-opengl-context-on-macos-to-not-be-forward-compatible/1108/3 "2024-03-02T11:28:03Z")
I believe on macOS you cannot have an OpenGL 3.x context with the compatibility profile. The GL drivers on macOS do not support that configuration. I’d you ask for compatibility profile, you must use OpenGL 2.x.
---
### Author:  [@bes](https://discourse.gstreamer.org/u/bes)
#### Post date: [March 2, 2024, 12:46pm UTC](https://discourse.gstreamer.org/t/how-do-i-configure-the-opengl-context-on-macos-to-not-be-forward-compatible/1108/4 "2024-03-02T12:46:43Z")
Alright, gotcha.
But it seems the forward-compatibility bit is available, since glfw is using that on macos?
See [Fixes opengl3 examples on OSX by gordonmcshane · Pull Request #229 · ocornut/imgui · GitHub](https://github.com/ocornut/imgui/pull/229)
---
### Author:  [@ystreet00](https://discourse.gstreamer.org/u/ystreet00)
#### Post date: [March 2, 2024, 10:45pm UTC](https://discourse.gstreamer.org/t/how-do-i-configure-the-opengl-context-on-macos-to-not-be-forward-compatible/1108/5 "2024-03-02T22:45:19Z")
If you request an opengl3 context you are requesting a “forward-compatible” context. If you request an opengl context, you are not.
---
### Author:  [@bes](https://discourse.gstreamer.org/u/bes)
#### Post date: [March 3, 2024, 7:19am UTC](https://discourse.gstreamer.org/t/how-do-i-configure-the-opengl-context-on-macos-to-not-be-forward-compatible/1108/6 "2024-03-03T07:19:36Z")
There are nuances though, but I think I found a source that agrees with you.
First about the nuances
# Profiles
For OpenGL (3.2+?) there are two profiles - `core` and `compatibility`, these profiles could theoretically be available at any OpenGL version at or above 3.2, but it seems like macOS maybe doesn’t implement it this way.
# “Forward-compatibility bit”
It seem like it’s allowed in the spec to request a `core` profile _with_ a forward-compatibility bit set to false. However, the [Khronos wiki](https://www.khronos.org/opengl/wiki/OpenGL_Context#Forward_compatibility) states:
> You should use the forward compatibility bit only if you need compatibility with MacOS. That API requires the forward compatibility bit to create any core profile context.
So you can’t create a `core` profile on macOS without setting `forward-compatibility=true`.
# Conclusion
I’ve been reading all over different sources that `core` can be created with the `forward-compatibility` “bit” set to false. This isn’t possible on macOS, and that’s the important distinction I did not understand until now.
Thank you for your help ❤
EDIT: added the source