glcontext: require a shader version to initialize.

It's very near pointless to try our GL implementation without shaders.

https://bugzilla.gnome.org/show_bug.cgi?id=749284

diff --git a/gst-libs/gst/gl/gstglcontext.c b/gst-libs/gst/gl/gstglcontext.c
index 8a71df1..98ed0ed 100644 (file)
--- a/gst-libs/gst/gl/gstglcontext.c
+++ b/gst-libs/gst/gl/gstglcontext.c
@@ -1101,7 +1101,8 @@ _create_context_info (GstGLContext * context, GstGLAPI gl_api, gint * gl_major,
 
   gl = context->gl_vtable;
 
-  if (!gl->GetString || !gl->GetString (GL_VERSION)) {
+  if (!gl->GetString || !gl->GetString (GL_VERSION)
+      || !gl->GetString (GL_SHADING_LANGUAGE_VERSION)) {
     g_set_error (error, GST_GL_CONTEXT_ERROR, GST_GL_CONTEXT_ERROR_FAILED,
         "glGetString not defined or returned invalid value");
     return FALSE;