[Rd] Best way for rgl's .onLoad to fail?

[Henrik Bengtsson]

If I recall it correctly, at least on Linux, rgl only needs X11 when
rgl.useNULL(FALSE).  Is that correct?  If so, I would say dependency
on X11 is optional and therefore you should be able to load the
package even without X11.  Or is it that it still requires X11 libs
but not an X11 server?

My $.02

/Henrik

On Mon, Feb 1, 2016 at 1:44 AM, Duncan Murdoch <murdoch.duncan at gmail.com> wrote:
> On 01/02/2016 4:26 AM, Martin Maechler wrote:
>>>>>>>
>>>>>>> "BH" == Bryan Hanson <hanson at depauw.edu>
>>>>>>>      on Sun, 31 Jan 2016 09:50:46 -0500 writes:
>>
>>
>>      BH> I think the 2nd option will be more palatable to
>>      BH> inexperienced users, but both do state the important
>>      BH> detail.  Bryan
>>
>>      >> On Jan 30, 2016, at 4:11 PM, Duncan Murdoch
>> <murdoch.duncan at gmail.com> wrote:
>>      >>
>>      >> On OSX and Linux, the rgl package currently requires X11
>>      >> libs to be available for linking.  Recent versions of OSX
>>      >> don't include them by default, so I'd like rgl to fail
>>      >> nicely.
>>      >>
>>      >> Ideally, it will load a library that doesn't need to link
>>      >> to the X11 libs but will still allow WebGL code to work,
>>      >> but that's complicated, so I'd like a stopgap.
>>      >>
>>      >> I can detect that the failure is about to happen, and
>>      >> call stop() in the .onLoad hook, but that gives an ugly
>>      >> message:
>>      >>
>>      >> > library(rgl)
>>      >> Error : .onLoad failed in loadNamespace() for 'rgl', details:
>>      >> call: NULL
>>      >> error: X11 not found; XQuartz (from www.xquartz.org) is required
>> to run rgl.
>>      >> Error: package or namespace load failed for ‘rgl’
>>
>> I agree that the error message is a bit messy or even ugly,
>> however, other than Bryan, I would want  library(.)  to signal
>> an error when it cannot provide a working package, loaded and
>> attached to search().
>>
>> Other functions, such as  require(.)  do rely on this behavior of
>> library(.),
>> e.g., the much used idiom
>>
>>    if(require(<some package>)) {
>>        ....
>>        ....
>>        ....
>>    }
>>
>> needs library() to signal an error on  non-success.
>
>
> Yes, that's a good point.  That's what the version on R-forge currently
> does.
>
> Duncan Murdoch
>
>
>>
>> Martin
>>
>>      >> Alternatively, I can just give a warning and not attempt to load
>> the rgl lib:
>>      >>
>>      >> > library(rgl)
>>      >> Warning message:
>>      >> X11 not found; XQuartz (from www.xquartz.org) is required to run
>> rgl.
>>      >>
>>      >> rgl is now loaded, but it doesn't work; just about any function
>> call will give an error, e.g.
>>      >>
>>      >> > plot3d(1,2,3)
>>      >> Error in rgl.cur() : object 'rgl_dev_getcurrent' not found
>>      >>
>>      >> Do people have opinions about this?
>>      >>
>>      >> One comparable package is RGtk2:  if Gtk2 isn't install, it offers
>> to install it.  I could probably do that for XQuartz.  If the user says no,
>> RGtk2 gives really ugly error messages.  rgl can work without XQuartz, but
>> as I already mentioned, making this work is complicated, so I'd like
>> something simple for now.
>>      >>
>>      >> Duncan Murdoch
>>      >>
>>      >> ______________________________________________
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>>
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>
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