[Rd] inconsistency/bug in recordPlot/replayPlot

[Gabriel Becker]

Hey all,

I've run accross what seems to be a bug in the recordPlot/replayPlot
functionality (or at least the lack of a feature which seems pretty
reasonable to expect to be there)

When drawing to a file-based graphics device (I tested with png()), the
file resulting from calling replayPlot on a recordedplot object does not
contain an identical image to that captured by the same graphics device
when used on the plot that was recorded.

Reproducible (at least for me on linux) example:

png("noreplay.png")
plot(1:10)
dev.off()

plot(1:10)
recplot = recordPlot()
png("withreplay.png")
replayPlot(recplot)
dev.off()

The resulting png files are attached. You'll notice that the noreplay.png
has the expected white background, while withoutreplay.png has no/a
transparent background.

This seems likely to be related to the note in ?dev.print :
"
 Note that these functions copy the _device region_ and not a plot:
     the background colour of the device surface is part of what is
     copied.  Most screen devices default to a transparent background,
     which is probably not what is needed when copying to a device such
     as ‘png’.
"

Now this may be as intended because it is "not allowed" to draw
recordedplot objects to devices other than the one they were recorded on
(AFAIK the primary purpose of recordedplot objects is fast redraws
internally), but alas that is what my use-case calls for. Furthermore,  I
don't think I'm alone in thinking wistfully about how useful it would be to
have an actual, transportable object class which can fully represent an R
plot in any R-based context.

I'm pretty sure I can compile a patch which does this if it would be
considered, though there would be a delay of a week or two before I could
burrow out from under the mound of other stuff I currently need to be doing

sessionInfo below, and I have also confirmed that the behavior remains
unchanged in the current trunk.

Thanks,
~G

> sessionInfo()
R version 3.0.1 (2013-05-16)
Platform: x86_64-pc-linux-gnu (64-bit)

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C
 [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8
 [5] LC_MONETARY=en_US.UTF-8    LC_MESSAGES=en_US.UTF-8
 [7] LC_PAPER=C                 LC_NAME=C
 [9] LC_ADDRESS=C               LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

loaded via a namespace (and not attached):
[1] compiler_3.0.1 tools_3.0.1

-- 
Gabriel Becker
Graduate Student
Statistics Department
University of California, Davis
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