[R-pkg-devel] Issue with use of par() in package
Jan van der Laan
rhe|p @end|ng |rom eoo@@dd@@n|
Fri Aug 22 18:18:28 CEST 2025
Thanks Micheal and Martin,
I have contacted the people from CRAN, and they have let me know that in
this case it is indeed reasonable to set par and not set it back.
I will also think about Martins suggestion. Currently I return an other
object, but I might be able to add the old par-values to that.
Thanks.
Best,
Jan
On 8/22/25 09:14, Martin Maechler wrote:
>>>>>> Michael Chirico
>>>>>> on Thu, 21 Aug 2025 12:56:41 -0700 writes:
>
> > I can understand caution about functions with side effects, but rejecting a
> > package on those grounds alone seems strange to me.
>
> > I can easily find thousands of calls to par() on CRAN without any
> > associated on.exit() cleanup ([1] [2] [3] [4] with a full regex search [5])
>
> > [1]
> > https://github.com/cran/raster/blob/3f64977b51a3b7c565f1309a462cb35f66daeafe/R/hist.R#L44
> > [2]
> > https://github.com/cran/quantreg/blob/43abb16645d5e78d1377896ebd19d760efd2ace9/R/khmal.R#L107-L115
> > [3]
> > https://github.com/cran/SensoMineR/blob/c9a159cb445e538c953d27de54288897882b3c91/R/barrow.R#L1
> > [4]
> > https://github.com/cran/GD/blob/1ce7c3c8b63dafb1d9d0a9e2ffcd6af4917fa077/R/sesu.R#L25
> > [5]
> > https://github.com/search?q=org%3Acran+%2F%5Cn%5B%5E%23%5D*%5B%5E%5Cw.%5Dpar%5C%28%5B+%5Cn%5D*%5B%5E.%29+%5Cn%22%27%5D%2F+path%3A%2F%5C.R%24%2F+NOT+%22on.exit%22+NOT+path%3A%2Fdemo%2F+NOT+path%3A%2Ftests%2F&type=code
>
> > I see no reference to 'par' inside {tools} (in particular QC.R), so R CMD
> > check is not looking for this.
>
> > IMO, clearly documenting the side effects of any such functions is more
> > than enough.
>
> > Mike C
>
> I agree.
> I've also been authoring a package with one function whose
> *purpose* it is to modify par() conveniently.
> The function is very old (older than R; I wrote it for S /
> S-plus in my first post-doc year in 1990:
> https://search.r-project.org/CRAN/refmans/sfsmisc/html/mult.fig.html
>
> It *is* however careful to return the previous par() {in <result>$old.par }
> such that when you use mult.fig() in a function or an R script, you can easily
> add an on.exit() in your function or use par(<....>) directly to revert the global par()
> to its original values.
>
> Martin
>
>
> > On Thu, Aug 21, 2025 at 1:45 AM Jan van der Laan <rhelp using eoos.dds.nl> wrote:
>
> >>
> >>
> >> Someone asked for the response I got from CRAN. I included it below:
> >>
> >> ---
> >> [... another issue where I forgot a \value{} in the documentation of one
> >> of the functions]
> >>
> >> Please make sure that you do not change the user's options, par or
> >> working directory. If you really have to do so within functions, please
> >> ensure with an *immediate* call of on.exit() that the settings are reset
> >> when the function is exited.
> >> e.g.:
> >> ...
> >> oldpar <- par(no.readonly = TRUE) # code line i
> >> on.exit(par(oldpar)) # code line i + 1
> >> ...
> >> par(mfrow=c(2,2)) # somewhere after
> >> ...
> >> e.g.: -> R/tgp.R
> >> If you're not familiar with the function, please check ?on.exit. This
> >> function makes it possible to restore options before exiting a function
> >> even if the function breaks. Therefore it needs to be called immediately
> >> after the option change within a function.
> >> For more details:
> >> <
> >> https://contributor.r-project.org/cran-cookbook/code_issues.html#change-of-options-graphical-parameters-and-working-directory
> >> >
> >>
> >> Please fix and resubmit.
> >> ---
> >>
> >> I understand why this is asked and I also know how to handle this in
> >> usual cases. I am not sure how to handle this in the specific case here.
> >> Perhaps I missed some alternative way of handling this.
> >>
> >> Best,
> >> Jan
> >>
> >>
> >> On 8/20/25 21:31, Jan van der Laan wrote:
> >> > I recently submitted a package to CRAN that creates a device that
> >> > outputs into the terminal (for terminals that support the Terminal
> >> > Graphics Protocol (and hopefully in the future also terminals that
> >> > support sixel)) [1].
> >> >
> >> > It introduces a 'tgp' function that does the following:
> >> >
> >> > 1. It opens a ragg::agg_capture device.
> >> >
> >> > 2. When term_col = TRUE: sets the background and foreground colors of
> >> > the device to those of the terminal (when these can be detected).
> >> >
> >> > 3. Every time the ragg:agg_capture device is updated: updates the plot
> >> > in the terminal.
> >> >
> >> > Point 2 raises an issue from CRAN as par() changes some properties and
> >> > these are not set back at the and of the function call. This is
> >> > intentional, as otherwise setting them would be useless; it is the
> >> > intention that the colors of subsequent plot calls are changed. I am
> >> > not sure how I can set the colors of the device to those in the terminal
> >> > (as requested by the user) without violating this rule.
> >> >
> >> > Are there alternative ways of helping the user to set the colors of the
> >> > device without violating this issue?
> >> >
> >> > Could this be an exception to the rule as the argument intentionally
> >> > changes par()? This could be made more explicit by changing the default
> >> > value to FALSE. I guess this question is better asked at the CRAN
> >> > maintainers, but perhaps there are other package that do something
> >> > similar that I might look at.
> >> >
> >> > Instead of having this functionality in the tgp() function, I could
> >> > create a 'set_figure_colours_to_terminal()` function (perhaps with a
> >> > corresponding reset function). However, this function would run into the
> >> > same issue.
> >> >
> >> > I appreciate any suggestions/help that yoy could give.
> >> >
> >> > Best,
> >> > Jan
> >> >
> >> >
> >> >
> >> >
> >> > [1] The current version of the code can be found here: https://
> >> > codeberg.org/djvanderlaan/terminalgraphics/src/branch/dev
> >> >
> >> > ______________________________________________
> >> > R-package-devel using r-project.org mailing list
> >> > https://stat.ethz.ch/mailman/listinfo/r-package-devel
> >>
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> >>
>
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>
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