-// that is needed by various components. (In time, for instance, we will query
-// about extensions here.)
-void init_movit();
+// that is needed by various components. For instance, it verifies that
+// we have all the OpenGL extensions we need.
+//
+// The first parameter gives which directory to read .frag files from.
+// This is a temporary hack until we add something more solid.
+//
+// The second parameter specifies whether debugging is on or off.
+// If it is on, Movit will write intermediate graphs and the final
+// generated shaders to the current directory.
+//
+// If you call init_movit() twice with different parameters,
+// only the first will count.
+void init_movit(const std::string& data_directory, MovitDebugLevel debug_level);