[Rd] Re: [R] Problem going back to a viewport with gridBase

[Gabor Grothendieck]

Thanks.  Yet one other comment to consider when thinking
about this.  Even if its not possible
or advisable to guarantee order, even without the hash=
idea, it may be possible to guarantee that default names
are generated in some order that can be used by
getChildren to ensure that it returns the children in
the same order they are created or perhaps even some sort
of timestamp can be attached to objects to facilitate 
later traversal.

On 6/7/05, Paul Murrell <p.murrell at auckland.ac.nz> wrote:
> Hi
> 
> 
> Gabor Grothendieck wrote:
> > Here is the code once again.  This time I have supplied two
> > names methods and a getChildren.viewport function to
> > encapsulate the corresponding grid internals.  It would
> > be easiest if grid provided these itself but in the absence
> > of that this does encapsulate dependencies on grid
> > internals to a well defined set of functions.   Note that
> > names is only used in 'with' and 'with' will be eliminated
> > once Deepayan adds the use.viewport= (or whatever
> > its called) to print.   I am not sure from your response
> > whether or not you intend to add these items to the grid
> > API but in any case this provides an intermediate
> > level of safety.
> 
> 
> Yep, I've made a note to look at adding these to the grid API.
> Thanks.
> 
> Paul
> 
> 
> > library(grid)
> > library(lattice)
> >
> > pushLayout <- function(nr, nc, name="layout") {
> >   pushViewport(viewport(layout=grid.layout(nr, nc), name=name))
> >   for (i in 1:nr) {
> >     for (j in 1:nc) {
> >       pushViewport(viewport(layout.pos.row=i, layout.pos.col=j))
> >       upViewport()
> >     }
> >   }
> >   upViewport()
> > }
> >
> > names.vpPath <- names.viewport <- function(x) x$name
> >
> > with.vpPath <- with.viewport <- function(data, expr, ...) {
> >       # if data is a vpPath it cannot be ROOT since
> >       # NULL will never dispatch here
> >       depth <- if (data$name == "ROOT") 0 else downViewport(names(data))
> >       result <- eval.parent(substitute(expr))
> >       upViewport(depth)
> >       invisible(result)
> > }
> >
> > getChildren.viewport <- function(x) x$children
> >
> > grid.newpage()
> >
> > # specify number of cells to fill and number of rows
> > n <- 5; nr <- 3
> >
> > nc <- ceiling(n/nr)
> > downViewport(pushLayout(nr, nc))
> >
> > vpt <- current.vpTree(all = FALSE)
> > for(k in 1:n) with(getChildren.viewport(vpt)[[k]],
> >       print( xyplot(v ~ v, list(v = 1:k)), newpage = FALSE )
> > )
> 
> 
> --
> Dr Paul Murrell
> Department of Statistics
> The University of Auckland
> Private Bag 92019
> Auckland
> New Zealand
> 64 9 3737599 x85392
> paul at stat.auckland.ac.nz
> http://www.stat.auckland.ac.nz/~paul/
> 
>