gl_common: properly reject old OpenGL versions

The extension checking logic was broken, which reported OpenGL 3 if the
OpenGL .so exported OpenGL 3-only symbols, even if the reported OpenGL
version is below 3.0. Fix it and simplify the code a bit. Also never
fail hard if required functions are not found. The caller should check
the capability flags instead. Give up on the idea that we should print
a warning if essential functions are not found (makes loading of ancient
legacy-only extensions easier).

This was experienced with the following version strings:

OpenGL vendor string: Intel Open Source Technology Center
OpenGL renderer string: Mesa DRI Intel(R) 915GM x86/MMX/SSE2
OpenGL version string: 1.4 Mesa 9.0.1

(Possibly reports a very old version because it has no GLSL support,
and thus isn't even GL 2.0 compliant.)

1 files changed, 20 insertions, 11 deletions

diff --git a/video/out/gl_common.c b/video/out/gl_common.c
index 06c208f36e..00e21ff312 100644
--- a/video/out/gl_common.c
+++ b/video/out/gl_common.c
@@ -655,11 +655,20 @@ static void getFunctions(GL *gl, void *(*getProcAddress)(const GLubyte *),
         if (gl3 && section->ver_removed && gl->version >= section->ver_removed)
             continue;
 
-        bool must_exist = section->ver_core && gl->version >= section->ver_core
-                          && !section->partial_ok;
+        // NOTE: Function entrypoints can exist, even if they do not work.
+        //       We must always check extension strings and versions.
 
-        if (!must_exist && section->extension &&
-            !strstr(gl->extensions, section->extension))
+        bool exists = false;
+        if (section->ver_core)
+            exists = gl->version >= section->ver_core;
+
+        if (section->extension && strstr(gl->extensions, section->extension))
+            exists = true;
+
+        if (section->partial_ok)
+            exists = true; // possibly
+
+        if (!exists)
             continue;
 
         void *loaded[MAX_FN_COUNT] = {0};
@@ -677,13 +686,13 @@ static void getFunctions(GL *gl, void *(*getProcAddress)(const GLubyte *),
                 ptr = fn->fallback;
             if (!ptr) {
                 all_loaded = false;
-                if (must_exist) {
-                    // Either we or the driver are not conforming to OpenGL.
-                    mp_msg(MSGT_VO, MSGL_ERR, "[gl] Required function '%s' not "
-                           "found.\n", fn->funcnames[0]);
-                    talloc_free_children(gl);
-                    *gl = (GL) {0};
-                    return;
+                if (!section->partial_ok) {
+                    mp_msg(MSGT_VO, MSGL_V, "[gl] Required function '%s' not "
+                           "found for %s/%d.%d.\n", fn->funcnames[0],
+                           section->extension ? section->extension : "native",
+                           MPGL_VER_GET_MAJOR(section->ver_core),
+                           MPGL_VER_GET_MINOR(section->ver_core));
+                    break;
                 }
             }
             assert(i < MAX_FN_COUNT);