mesa: simplify MESA_GL_VERSION_OVERRIDE behavior of API override

v2:
 - Provide a correct explanation on the envvars documentation (Ian).
 - Provide a more correct explanation on the function comments (Andres).
v3:
 - Homogenize documentation and inline comments (Emil).
 - Correct a typo (Emil).

Fixes: 2599b92eb97 ("mesa: allow forcing >=3.1 compatibility contexts
with MESA_GL_VERSION_OVERRIDE")

Cc: Jordan Justen <[email protected]>
Cc: Ian Romanick <[email protected]>
Cc: Eric Engestrom <[email protected]>
Cc: Emil Velikov <[email protected]>
Reviewed-by: Emil Velikov <[email protected]>

1 files changed, 11 insertions, 12 deletions

diff --git a/src/mesa/main/version.c b/src/mesa/main/version.c
index a28069054d3..3b51b1e7a36 100644
--- a/src/mesa/main/version.c
+++ b/src/mesa/main/version.c
@@ -139,11 +139,15 @@ create_version_string(struct gl_context *ctx, const char *prefix)
  *
  * Example uses of MESA_GL_VERSION_OVERRIDE:
  *
- * 2.1: select a compatibility (non-Core) profile with GL version 2.1
- * 3.0: select a compatibility (non-Core) profile with GL version 3.0
- * 3.0FC: select a Core+Forward Compatible profile with GL version 3.0
- * 3.1: select a Core profile with GL version 3.1
- * 3.1FC: select a Core+Forward Compatible profile with GL version 3.1
+ * 2.1: select a compatibility (non-Core) profile with GL version 2.1.
+ * 3.0: select a compatibility (non-Core) profile with GL version 3.0.
+ * 3.0FC: select a Core+Forward Compatible profile with GL version 3.0.
+ * 3.1: select GL version 3.1 with GL_ARB_compatibility enabled per the driver default.
+ * 3.1FC: select GL version 3.1 with forward compatibility and GL_ARB_compatibility disabled.
+ * 3.1COMPAT: select GL version 3.1 with GL_ARB_compatibility enabled.
+ * X.Y: override GL version to X.Y without changing the profile.
+ * X.YFC: select a Core+Forward Compatible profile with GL version X.Y.
+ * X.YCOMPAT: select a Compatibility profile with GL version X.Y.
  */
 bool
 _mesa_override_gl_version_contextless(struct gl_constants *consts,
@@ -157,17 +161,12 @@ _mesa_override_gl_version_contextless(struct gl_constants *consts,
    if (version > 0) {
       *versionOut = version;
 
-      /* If the API is a desktop API, adjust the context flags.  We may also
-       * need to modify the API depending on the version.  For example, Mesa
-       * does not support a GL 3.3 compatibility profile.
-       */
+      /* Modify the API and context flags as needed. */
       if (*apiOut == API_OPENGL_CORE || *apiOut == API_OPENGL_COMPAT) {
          if (version >= 30 && fwd_context) {
             *apiOut = API_OPENGL_CORE;
             consts->ContextFlags |= GL_CONTEXT_FLAG_FORWARD_COMPATIBLE_BIT;
-         } else if (version >= 31 && !compat_context) {
-            *apiOut = API_OPENGL_CORE;
-         } else {
+         } else if (compat_context) {
             *apiOut = API_OPENGL_COMPAT;
          }
       }