Mac OS X tcltk/X11 issues

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: G?bor Cs?rdi [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