R devel - Mar 2013 - How to avoid using gridextra via Depends instead of Imports in a package ?

Hello,

I really need some insight on a problem we encountered using grid,
lattice and gridExtra.

I tried to reduce the problem, so the plot make no sense.

we have a package: gridextrabug

with:

DESCRIPTION
------------------
Package: gridextrabug
Title: gridextrabug
Version: 0.1
Author: toto
Maintainer: toto <karl.forner at quartzbio.com>
Description: gridextrabug
Imports:
    grid,
    gridExtra,
    lattice,
    latticeExtra,
    reshape,
Depends:
    R (>= 2.15),
    methods
Suggests:
    testthat,
    devtools
License: GPL (>= 3)
Collate:
    'zzz.R'
    'plotFDR.R'

R/plotFDR.R
----------------
plot_fdr <- function(dt,qvalue_col,pvalue_col, zoom_x=NULL, zoom_y=NULL,
		fdrLimit=0,overview_plot=FALSE,...)
{
		
	frm <- as.formula(paste(qvalue_col,"~
rank(",pvalue_col,")"))
	plt <- xyplot( frm ,
			data=dt,
			abline=list(h=fdrLimit,lty="dashed"),
			pch=16,cex=1,
			type="p",
			panel=panelinplot2,
			subscripts= TRUE,

        )
	
	return(plt)
}

panelinplot2 <- function(x,y,subscripts,cex,type,...){

    panel.xyplot(x,y,subscripts=subscripts,
        ylim=c(0,1),
        type=type,
        cex=cex,...)
    pltoverview <- xyplot(y~x,xlab=NULL,
        ylab=NULL,
        type="l",
        par.settings=qb_theme_nopadding(),
        scales=list(draw=FALSE),
        cex=0.6,...)
    gr <- grob(p=pltoverview, ..., cl="lattice")


    grid.draw(gr) # <-----------------------------------------------
problematic call
}

NAMESPACE
------------------
export(panelinplot2)
export(plot_fdr)
importFrom(grid,gpar)
importFrom(grid,grid.draw)
importFrom(grid,grid.rect)
importFrom(grid,grid.text)
importFrom(grid,grob)
importFrom(grid,popViewport)
importFrom(grid,pushViewport)
importFrom(grid,unit)
importFrom(grid,viewport)
importFrom(gridExtra,drawDetails.lattice)
importFrom(lattice,ltext)
importFrom(lattice,panel.segments)
importFrom(lattice,panel.xyplot)
importFrom(lattice,stripplot)
importFrom(lattice,xyplot)
importFrom(latticeExtra,as.layer)
importFrom(latticeExtra,layer)
importFrom(reshape,sort_df)

Then if you execute this script:

without_extra.R
------------------
library(gridextrabug)
p <- seq(10^-10,1,0.001)
p <- p[sample(1:length(p))]
q <- p.adjust(p, "BH")
df <- data.frame(p,q)


plt <-	plot_fdr(df,qvalue_col= "q", pvalue_col="p",
    zoom_x=c(0,20),
    fdrLimit=0.6,
    overview_plot=TRUE)
X11()
print(plt)

you will not have the second plot corresponding the call to panelinplot2


If you execute this one:

with_extra.R
------------------
library(gridextrabug)
p <- seq(10^-10,1,0.001)
p <- p[sample(1:length(p))]
q <- p.adjust(p, "BH")
df <- data.frame(p,q)


plt <-	plot_fdr(df,qvalue_col= "q", pvalue_col="p",
    zoom_x=c(0,20),
    fdrLimit=0.6,
    overview_plot=TRUE)
X11()

library(gridExtra)
print(plt)

you will have the second plot.

>From what I understood, the last line of panelinplot2(), "
grid.draw(x)", dispatches to  grid:::grid.draw.grob(), which in turn
calls grid:::drawGrob(), which calls grid::drawDetails() which is a S3
generic.
The gridExtra package defines the method drawDetails.lattice().
When the package is loaded in the search() path,  the "grid.draw(x)"
call dispatches to gridExtra:::drawDetails.lattice().

We would rather avoid messing with the search path, which is a best
practice if I'm not mistaken, so we tried hard to solve it using
Imports.
But I came to realize that the problem was in the grid namespace, not
in our package namespace.

I tested it with the following work-around:
parent.env(parent.env(getNamespace('grid'))) <-
getNamespace('gridExtra')

which works.

So my questions are:
  * did we miss something obvious ?
  * what is the proper way to handle this situation ?


Thanks in advance for your wisdom.

Karl Forner