update   xtlang

(bind-func update
  (lambda (tex:Texture*)
    (glActiveTexture GL_TEXTURE0)
    (glBindTexture GL_TEXTURE_2D (id tex))
    (glTexImage2D GL_TEXTURE_2D 0
                  (if (= (type tex) GL_BGRA) GL_RGBA (type tex)) ;; this is internal type
                  (width tex)
                  (height tex)
                  0
                  (type tex) ;; this is external type (i.e. conversion from external to internal required)
                  GL_UNSIGNED_BYTE
                  (data tex))
    (glBindTexture GL_TEXTURE_2D 0)
    (gl_print_error "couldn't update texture")
    void))