[R-SIG-Mac] Mac OS X tcltk/X11 issues

[John Fox]

Dear Gabor,

As I just explained, the problem isn't testing for X11, which I know how to do -- though capabilities("X11") is a bit better than what I suggested. The issue is specific to Mac OS X because the Windows implementation of R includes a Tcl/Tk that doesn't use X11, and I've never seen the problem on Linux.

Best,
 John

> -----Original Message-----
> From: Gábor Csárdi [mailto:csardi.gabor at gmail.com]
> Sent: Monday, July 14, 2014 6:37 PM
> To: Marc Schwartz
> Cc: John Fox; urbanek at research.att.com; R-SIG-Mac
> Subject: Re: [R-SIG-Mac] Mac OS X tcltk/X11 issues
> 
> What's wrong with capabilities("X11")?
> 
> I am not sure if teting for the OS, and especially for a particular X
> server, installed in a particular directory, is a good idea, even if
> it covers most of the _current_ installations.
> 
> Gabor
> 
> On Mon, Jul 14, 2014 at 6:13 PM, Marc Schwartz <marc_schwartz at me.com>
> wrote:
> >
> > On Jul 14, 2014, at 4:53 PM, Marc Schwartz <marc_schwartz at me.com>
> wrote:
> >
> >> On Jul 14, 2014, at 4:13 PM, John Fox <jfox at mcmaster.ca> wrote:
> >>
> >>> Dear Simon and list members,
> >>>
> >>> As many of you are aware, when X11 isn't installed on Mac OS X,
> loading the
> >>> tcltk package produces an error, with a message that many users
> find
> >>> cryptic. There was yet another instance of this problem reported to
> the list
> >>> today.
> >>>
> >>> I'm interested in the issue because the Rcmdr package uses tcltk
> and thus
> >>> fails to load when X11 is absent. Rcmdr users tend to be
> inexperienced and
> >>> so, unless they find their way to the Rcmdr installation webpage,
> where
> >>> detailed installation instructions are provided, they tend to be
> stymied by
> >>> the problem.
> >>>
> >>> If I could, I'd intercept the problem by checking
> capabilities()["X11"] in
> >>> the Rcmdr .onLoad() or .onAttach() function, but because the Rcmdr
> package
> >>> imports the tcltk namespace, the error occurs before these startup
> functions
> >>> are executed -- a chicken-and-egg problem.
> >>>
> >>> It occurs to me that tcltk could fail more gracefully on Mac OS X
> when X11
> >>> is absent, perhaps popping up a webpage in a browser with
> instructions and a
> >>> link for installing XQuartz. I'd do this myself in the Rcmdr
> package if I
> >>> could. Or tcltk could check for the presence of X11 and not try to
> start it
> >>> if it's absent, reporting a warning rather than throwing an error.
> >>>
> >>> Alternatively, I'd be grateful if someone could suggest how I might
> detect
> >>> the problem in the Rcmdr package before loading fails. The only
> thing that I
> >>> could think of was writing a separate RcmdrInstall package that
> bypasses
> >>> tcltk, but that would be awkward and would only help users who
> discovered
> >>> that RcmdrInstall exists.
> >>>
> >>> Thanks,
> >>> John
> >>
> >>
> >> John,
> >>
> >> Is there someplace in your startup process where you could run code
> along the lines of:
> >>
> >> if (grepl("apple", R.version$platform) &
> length(list.files("/opt/X11/bin", pattern = "Xquartz")) == 0) {
> >>     cat("X11 is required. Please visit http://xquartz.macosforge.org
> to download and install Xquartz.")
> >>     stop()
> >> }
> >>
> >>
> >> The above code will check to see if the user is running R on OS X
> and also if the Xquartz binary is present in the default location.
> >>
> >> Not sure if this is helpful.
> >
> >
> > A possible correction in the above code relative to detecting OS X:
> >
> > if ((Sys.info()["sysname"] == "Darwin") &
> length(list.files("/opt/X11/bin", pattern = "Xquartz")) == 0) {
> >     cat("X11 is required. Please visit http://xquartz.macosforge.org
> to download and install Xquartz.")
> >     stop()
> > }
> >
> >
> > I believe that Sys.info()["sysname"] == "Darwin" is preferred for
> detecting the OS that R is running on versus the OS that it was built
> upon according to the help files, if I read correctly. This could be
> important if someone is building R from source versus installing
> Simon's CRAN binary, I presume.
> >
> > Regards,
> >
> > Marc
> >
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