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
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