R help - Jan 2016 - R 3.2.3 on Windows 8.1 with interface scaling: how do I produce metafiles that fill the whole canvas?

To reproduce (requires Windows):

1) Set your desktop scaling to 100%;
2) run the script below;
3) observe that the chart in scaled-example.wmf takes up the whole canvas.
4) Set your desktop scaling to greater than 100% (try 150% or 200%);
5) again run the script below;
6) observe that the chart in scaled-example.wmf takes up less than the
whole canvas.

Increasingly, we're seeing users run R on machines with very
high-resolution screens and scaled displays.  How can we correct for
this effect within R?

Cheers,

- Peter

Script:

-- start --
egfr <- c(222.6,176.4)
outcome <- data.frame(egfr)
hgb <- c(141,134)
predictors <- data.frame(hgb)
title <- "eGFR vs. Hgb"
ylab <- "eGFR"
xlab <- "Hgb"
gr1<-file.path(path.expand('~'),"scaled-example.wmf")
win.metafile(gr1)
plot(predictors[[1]],outcome[[1]],main=title,ylab=ylab,xlab=xlab)
dev.off()
-- end --