[Rd] Problems caused by dev.off() behaviour

[Avi Gross]

Just pointing out that if you do not want to SEE an error message that is
otherwise harmless, one option in R is to let the error happen but arrange
to deal with it in some way including just suppressing the message.

On Tue, Oct 3, 2023, 5:27 AM Duncan Murdoch <murdoch.duncan using gmail.com>
wrote:

> On 02/10/2023 10:17 p.m., Trevor Davis wrote:
> >  > Thanks!  However, isn't length(dev.list()) == 0 when there are no
> > devices?  That's what I'm seeing on MacOS.
> >
> > Ifthere is only one graphics device then R should automatically set it
> > as the active graphics device so it isn't really necessary to manually
> > set it.  Although there wouldn't be any harm in manually setting it you
> > only really need to worry about setting the previous graphics device
> > when there are two or more devices open.
>
> Right, I see.  With some more fiddling, I've decided that I don't like
> the error you get if you try to close device 1, so here's the current
> version:
>
> safe.dev.off  <- function(which = dev.cur(), prev = dev.prev()) {
>    if (which != 1) {
>      force(prev)
>      grDevices::dev.off(which)
>    }
>    if (length(dev.list()))
>      dev.set(prev)
>    else
>      c("null device" = 1)
> }
>
> This does the dev.set even if there's only one device so it can return
> the resulting device number.
>
> Duncan Murdoch
>
> >
> > Trevor
> >
> > On Mon, Oct 2, 2023 at 5:25 PM Duncan Murdoch <murdoch.duncan using gmail.com
> > <mailto:murdoch.duncan using gmail.com>> wrote:
> >
> >     Thanks!  However, isn't length(dev.list()) == 0 when there are no
> >     devices?  That's what I'm seeing on MacOS.
> >
> >     Duncan Murdoch
> >
> >     On 02/10/2023 4:21 p.m., Trevor Davis wrote:
> >      >  > Use it just like dev.off(), but it *will* restore the previous
> >     device.
> >      >
> >      > I'm observing that if there were no previously open graphics
> devices
> >      > then your `safe.dev.off()` opens up a new graphics device which
> >     may be
> >      > an undesired side effect (because "surprisingly" `dev.set()` on
> >     the null
> >      > graphics device opens up a new graphics device).  To avoid that
> you
> >      > could check if `dev.list()` is greater than length 1L:
> >      >
> >      >     safe.dev.off  <- function(which = dev.cur(), prev =
> dev.prev()) {
> >      >       force(prev)
> >      >       dev.off(which)
> >      >       if (length(dev.list()) > 1L) {
> >      >         dev.set(prev)
> >      >       }
> >      >     }
> >      >
> >      > Trevor
> >      >
> >      > On Mon, Oct 2, 2023 at 11:54 AM Duncan Murdoch
> >     <murdoch.duncan using gmail.com <mailto:murdoch.duncan using gmail.com>
> >      > <mailto:murdoch.duncan using gmail.com
> >     <mailto:murdoch.duncan using gmail.com>>> wrote:
> >      >
> >      >     I found some weird behaviour and reported it as
> >      > https://bugs.r-project.org/show_bug.cgi?id=18604
> >     <https://bugs.r-project.org/show_bug.cgi?id=18604>
> >      >     <https://bugs.r-project.org/show_bug.cgi?id=18604
> >     <https://bugs.r-project.org/show_bug.cgi?id=18604>> and
> >      > https://github.com/yihui/knitr/issues/2297
> >     <https://github.com/yihui/knitr/issues/2297>
> >      >     <https://github.com/yihui/knitr/issues/2297
> >     <https://github.com/yihui/knitr/issues/2297>>, but it turns out it
> >      >     was user
> >      >     error.
> >      >
> >      >     The dev.off() function was behaving as documented, but it
> >     behaves in an
> >      >     unexpected (by me) way, and that caused the "bugs".
> >      >
> >      >     The issue is that
> >      >
> >      >          dev.off()
> >      >
> >      >     doesn't always result in the previous graphics device being
> made
> >      >     current.  If there are two or more other open graphics
> >     devices, it
> >      >     won't
> >      >     choose the previous one, it will choose the next one.
> >      >
> >      >     I'm letting people know because this might affect other
> >     people too.  If
> >      >     you use dev.off(), don't assume it restores the previous
> device!
> >      >
> >      >     Here's my little workaround alternative:
> >      >
> >      >         safe.dev.off  <- function(which = dev.cur(), prev =
> >     dev.prev()) {
> >      >           force(prev)
> >      >           dev.off(which)
> >      >           dev.set(prev)
> >      >         }
> >      >
> >      >     Use it just like dev.off(), but it *will* restore the
> >     previous device.
> >      >
> >      >     Duncan Murdoch
> >      >
> >      >     ______________________________________________
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> >      >
> >
>
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