glcontext: add vfunc to retrieve the OpenGL platform version

i.e. the version of EGL, GLX, etc implemented.

https://bugzilla.gnome.org/show_bug.cgi?id=774518

gst-libs/gst/gl/egl/gstglcontext_egl.c

@@ -64,6 +64,8 @@ static GstGLPlatform gst_gl_context_egl_get_gl_platform (GstGLContext *
     context);
 static gboolean gst_gl_context_egl_check_feature (GstGLContext * context,
     const gchar * feature);
+static void gst_gl_context_egl_get_gl_platform_version (GstGLContext * context,
+    gint * major, gint * minor);
 
 G_DEFINE_TYPE (GstGLContextEGL, gst_gl_context_egl, GST_TYPE_GL_CONTEXT);
 
@@ -93,6 +95,8 @@ gst_gl_context_egl_class_init (GstGLContextEGLClass * klass)
       GST_DEBUG_FUNCPTR (gst_gl_context_egl_check_feature);
   context_class->get_current_context =
       GST_DEBUG_FUNCPTR (gst_gl_context_egl_get_current_context);
+  context_class->get_gl_platform_version =
+      GST_DEBUG_FUNCPTR (gst_gl_context_egl_get_gl_platform_version);
 }
 
 static void
@@ -801,3 +805,13 @@ gst_gl_context_egl_get_current_context (void)
 {
   return (guintptr) eglGetCurrentContext ();
 }
+
+static void
+gst_gl_context_egl_get_gl_platform_version (GstGLContext * context,
+    gint * major, gint * minor)
+{
+  GstGLContextEGL *context_egl = GST_GL_CONTEXT_EGL (context);
+
+  *major = context_egl->egl_major;
+  *minor = context_egl->egl_minor;
+}

gst-libs/gst/gl/gstglcontext.c

@@ -193,6 +193,8 @@ static void _init_debug (void);
 
 static gpointer gst_gl_context_create_thread (GstGLContext * context);
 static void gst_gl_context_finalize (GObject * object);
+static void gst_gl_context_default_get_gl_platform_version (GstGLContext *
+    context, gint * major, gint * minor);
 
 struct _GstGLContextPrivate
 {
@@ -285,6 +287,8 @@ gst_gl_context_class_init (GstGLContextClass * klass)
 
   klass->get_proc_address =
       GST_DEBUG_FUNCPTR (gst_gl_context_default_get_proc_address);
+  klass->get_gl_platform_version =
+      GST_DEBUG_FUNCPTR (gst_gl_context_default_get_gl_platform_version);
 
   G_OBJECT_CLASS (klass)->finalize = gst_gl_context_finalize;
 
@@ -1696,6 +1700,40 @@ gst_gl_context_set_shared_with (GstGLContext * context, GstGLContext * share)
       _context_share_group_ref (share->priv->sharegroup);
 }
 
+static void
+gst_gl_context_default_get_gl_platform_version (GstGLContext * context,
+    gint * major, gint * minor)
+{
+  if (major)
+    *major = 0;
+  if (minor)
+    *minor = 0;
+}
+
+/**
+ * gst_gl_context_get_gl_platform_version:
+ * @context: a #GstGLContext
+ * @major: (out): return for the major version
+ * @minor: (out): return for the minor version
+ *
+ * Get the version of the OpenGL platform (GLX, EGL, etc) used.  Only valid
+ * after a call to gst_gl_context_create_context().
+ */
+void
+gst_gl_context_get_gl_platform_version (GstGLContext * context, gint * major,
+    gint * minor)
+{
+  GstGLContextClass *context_class;
+
+  g_return_if_fail (GST_IS_GL_CONTEXT (context));
+  g_return_if_fail (major != NULL);
+  g_return_if_fail (minor != NULL);
+  context_class = GST_GL_CONTEXT_GET_CLASS (context);
+  g_return_if_fail (context_class->get_gl_platform_version != NULL);
+
+  context_class->get_gl_platform_version (context, major, minor);
+}
+
 static GstGLAPI
 gst_gl_wrapped_context_get_gl_api (GstGLContext * context)
 {

gst-libs/gst/gl/gstglcontext.h

@@ -128,6 +128,7 @@ struct _GstGLContextClass {
   void          (*destroy_context)    (GstGLContext *context);
   void          (*swap_buffers)       (GstGLContext *context);
   gboolean      (*check_feature)      (GstGLContext *context, const gchar *feature);
+  void          (*get_gl_platform_version) (GstGLContext *context, gint *major, gint *minor);
 
   /*< private >*/
   gpointer _reserved[GST_PADDING];
@@ -184,6 +185,8 @@ GST_EXPORT
 gboolean      gst_gl_context_check_gl_version (GstGLContext * context, GstGLAPI api, gint maj, gint min);
 GST_EXPORT
 gboolean      gst_gl_context_check_feature (GstGLContext *context, const gchar *feature);
+GST_EXPORT
+void          gst_gl_context_get_gl_platform_version (GstGLContext * context, gint * major, gint * minor);
 
 GST_EXPORT
 guintptr      gst_gl_context_get_current_gl_context     (GstGLPlatform context_type);

gst-libs/gst/gl/x11/gstglcontext_glx.c

@@ -58,6 +58,8 @@ static gboolean gst_gl_context_glx_choose_format (GstGLContext *
 GstGLAPI gst_gl_context_glx_get_gl_api (GstGLContext * context);
 static GstGLPlatform gst_gl_context_glx_get_gl_platform (GstGLContext *
     context);
+static void gst_gl_context_glx_get_gl_platform_version (GstGLContext * context,
+    gint * major, gint * minor);
 
 struct _GstGLContextGLXPrivate
 {
@@ -97,6 +99,8 @@ gst_gl_context_glx_class_init (GstGLContextGLXClass * klass)
       GST_DEBUG_FUNCPTR (gst_gl_context_glx_get_proc_address);
   context_class->get_current_context =
       GST_DEBUG_FUNCPTR (gst_gl_context_glx_get_current_context);
+  context_class->get_gl_platform_version =
+      GST_DEBUG_FUNCPTR (gst_gl_context_glx_get_gl_platform_version);
 }
 
 static void
@@ -472,3 +476,13 @@ gst_gl_context_glx_get_current_context (void)
 {
   return (guintptr) glXGetCurrentContext ();
 }
+
+static void
+gst_gl_context_glx_get_gl_platform_version (GstGLContext * context,
+    gint * major, gint * minor)
+{
+  GstGLContextGLX *context_glx = GST_GL_CONTEXT_GLX (context);
+
+  *major = context_glx->priv->glx_major;
+  *minor = context_glx->priv->glx_minor;
+}