utextvpDynamic <- function(label,
                           x=.5, y=.5, default.units="npc",
                           just="centre", angle=0, 
                           name="utext") {
    if (!is.unit(x)) x <- unit(x, default.units)
    if (!is.unit(y)) y <- unit(y, default.units)
    gTree(label=label, x=x, y=y, just=just, angle=angle, 
          cl="utextvpDynamic", name=name)
}

makeContext.utextvpDynamic <- function(x) {
    x$childrenvp <- utextvp(x$label, x$x, x$y, 
                            just=x$just, angle=x$angle,
                            name=paste0(x$name, ".vp"))
    x
}

makeContent.utextvpDynamic <- function(x) {
    kids <- utextvpChildren(x$label, x$name)
    setChildren(x, kids)
}