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

[Duncan Murdoch]

On 01/02/2016 11:46 AM, Henrik Bengtsson wrote:
> 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?

The latter.  It links to lots of OpenGL and X11 entry points, it just 
never calls them.

The good but "complicated" solution is to build a library without those 
links, but that's not going to happen soon.

Duncan Murdoch
>
> 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
> >>      >>
> >>      >> ______________________________________________
> >>      >> R-devel at r-project.org mailing list
> >>      >> https://stat.ethz.ch/mailman/listinfo/r-devel
> >>
> >>      > ______________________________________________
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> >>      > https://stat.ethz.ch/mailman/listinfo/r-devel
> >>
> >
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