Working with layouts in grid

Working with layouts in grid

# example1 (using grobs instead of grid.*)
vp <- vpTree(
    parent=viewport(layout=grid.layout(nrow=2, ncol=2), name='parent'),
    children=vpList(
        viewport(layout.pos.row=1, layout.pos.col=1, name='vp1'),
        viewport(layout.pos.row=1, layout.pos.col=2, name='vp2')
    )
)
pushViewport(vp)
seekViewport('parent')
gs <- gList(
    rectGrob(height=.5, width=.5, vp='vp1'), 
    textGrob('sq1', vp='vp1'), 
    rectGrob(height=.5, width=.5, vp='vp2'),
    textGrob('sq2', vp='vp2')
)
grid.draw(gs)

# example 2 (custom grob)
graphics.off()
foursquareGrob <- function(labels, name=NULL, gp=NULL, vp=NULL) {
    grob(labels=labels, name=name, gp=gp, vp=vp, cl='foursquare')
}
preDrawDetails.foursquare <- function(x) {
    vp <- vpTree(
        parent=viewport(layout=grid.layout(nrow=2, ncol=2), name='parent'),
        children=vpList(
            viewport(layout.pos.row=1, layout.pos.col=1, name='vp1'),
            viewport(layout.pos.row=1, layout.pos.col=2, name='vp2')
        )
    )
    pushViewport(vp)
    seekViewport('parent')
}
drawDetails.foursquare <- function(x, ...) {
    gs <- gList(
        rectGrob(height=.5, width=.5, vp='vp1'), 
        textGrob(x$labels[1], vp='vp1'), 
        rectGrob(height=.5, width=.5, vp='vp2'),
        textGrob(x$labels[2], vp='vp2')
    )
    grid.draw(gs)
}
postDrawDetails.foursquare <- function(x) {
    popViewport()
}
grid.draw(foursquareGrob(labels=c('sq1', 'sq2')))

# example 3 (example2, but with parent viewport different from root)
graphics.off()
little.root <- viewport(height=.5, width=.5, name='root')
pushViewport(little.root)
grid.draw(foursquareGrob(labels=c('sq1', 'sq2'), vp=little.root))


# example 4 (without explicit viewports)
graphics.off()
boxGrob <- function(label, name, height=unit(.5, 'npc'), width=unit(.5, 'npc'), gp=NULL, vp=NULL) {
    grob(label=label, height=height, width=width, gp=gp, vp=vp, cl='box')
}
drawDetails.box <- function(x, ...) {
    grid.rect(height=x$height, width=x$width, gp=x$gp)
    grid.text(label=x$label)
}

x <- frameGrob(layout=grid.layout(nrow=2, ncol=2))
x <- placeGrob(x, boxGrob(label='sq1', height=.5, width=.5), row=1, col=1)
x <- placeGrob(x, boxGrob(label='sq2', height=.5, width=.5), row=1, col=2)
grid.draw(x)