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

[Duncan Murdoch]

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>> 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> and
>     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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