GL2 gl = context(ctx).getGL().getGL2();
if (index >= 0 && gl.isExtensionAvailable("GL_VERSION_1_3")) {
gl.glActiveTexture(index + GL.GL_TEXTURE0);
gl.glClientActiveTexture(GL.GL_TEXTURE0 + index);
// FIXME: GL_NV_register_combiners
// if (gl.isExtensionAvailable("GL_NV_register_combiners")) {
// jctx.setCurrentTextureUnit(index + GL.GL_TEXTURE0);
// jctx.setCurrentCombinerUnit(index + GL.GL_COMBINER0_NV);
// gl.glCombinerParameteriNV(GL.GL_NUM_GENERAL_COMBINERS_NV, index + 1);