Using layout, I can easily create panels.

op <- par(no.readonly = TRUE)
layout(matrix(1:3, nrow=1), widths=c(.8, 1.1, .8))
plot(1:20, 1:20, pch=19, cex=2, col=colfunc(20))
plot(1:20, 1:20, pch=19, cex=2, col=colfunc(20))
plot(1:20, 1:20, pch=19, cex=2, col=colfunc(20))
par(op)

However, when creating a plot with miniplot inside, such as a gradient,

plotfun <- () {
  colfunc <- colorRampPalette(c("red", "blue"))
  plot(1:20, 1:20, pch=19, cex=2, col=colfunc(20))
  fig. <- c(grconvertX(c(.5, 4.5), from="user", to="ndc"), 
            grconvertY(c(8, 19), from="user", to="ndc"))
  op <- par(fig=fig., mar=c(1, 1, 1, 1))  ## removed the new=TRUE to no avail
  plot.window(c(0, 1), c(0, 1))
  rasterImage(as.raster(matrix(colfunc(20), ncol=1)), 0, 0, 1, 1)
  lbsq <- seq.int(0, 1, l=5)
  axis(4, at=lbsq, pos=1, labels=FALSE, col=0, col.ticks=1, tck=-.1)
  mtext(lbsq, 4, .25, at=lbsq, las=2, cex=.6)
  mtext('foo', 3, -.125, cex=.6, adj=.1, font=2)
  par(op)
}

it leaves the layout.

op <- par(no.readonly=TRUE)
layout(matrix(1:3, nrow=1), widths=c(.8, 1.1, .8))
plotfun()
plotfun()
plotfun()
par(op)

I’m aware that layout is “totally incompatible with … par(mfrow)”. But I already tried par() which also didn’t work. Anyway I need something like layout since I have different widths. Any clues, how to do it?