gltk.program: bind attribute location before linking program

libs/gltk/gltk/program.d

@@ -230,6 +230,11 @@ class Program(string[string] uniforms = [], int[string] attributes = [])
      */
     public void link()
     {
+        static foreach(attribute_name, attribute_location; attributes)
+        {
+            glBindAttribLocation(m_id, attribute_location, attribute_name.toStringz());
+        }
+
         glLinkProgram(m_id);
 
         GLint link_status;
@@ -254,10 +259,6 @@ class Program(string[string] uniforms = [], int[string] attributes = [])
         {
             mixin("m_uniform_" ~ uniform_name ~ " = glGetUniformLocation(m_id, \"" ~ uniform_name ~ "\");");
         }
-        static foreach(attribute_name, attribute_location; attributes)
-        {
-            glBindAttribLocation(m_id, attribute_location, attribute_name.toStringz());
-        }
     }
 
     /**