On 2013-11-22 12:40-0000 Andrew Ross wrote:

>
> Alan,
>
> I've been testing your changes as I go on my Ubuntu system. One thing
> I noticed almost by accident is that your itk detection code requires a
> working X11 display. This is not actually required to build (although
> it obviously is to use). I only noticed because I was building via a
> ssh connection without X11 forwarding and I couldn't understand why
> itk was disabled.
>
> This is probably not an issue for most users, but it might be an issue
> for example on auto-builders as used by distributions like Debian. It
> would be nice if we could avoid that.
>

To Andrew and Orion:

I also address this to Orion because the issue may impact him as well.

I confirm the issue here in this simple way.

1. Use ssh -x to login to your own machine without X forwarding

2. Then execute the following:

tclsh
% package require Itk

which errors out with the message:

no display name and no $DISPLAY environment variable

On the other hand, if you do this with a normal login that allows X,
then "package require Itk" works although you do get an annoying blank
GUI that comes up, but that disappears again as soon as you exit.

The reason this issue impacts our build-system is that logic checks the 
consistency
of Tcl and friends using the "package require" command (including
"package require Itk"), see cmake/modules/tcl-related.cmake.

So if it appears to be impossible to have X display working properly
for some Linux distribution autobuilding environment, then I suggest
you implement an option in tcl-related.cmake (which normally defaults
to OFF but which would be ON when building Linux distribution packages
for PLplot) to skip the part of the logic that automatically
determines PLPLOT_ITK_VERSION using "package require Itk" and replace
that with some other method such as reading an environment variable
that packagers specify that contains the known (for that distribution)
Itk version.

Alan
__________________________
Alan W. Irwin

Astronomical research affiliation with Department of Physics and Astronomy,
University of Victoria (astrowww.phys.uvic.ca).

Programming affiliations with the FreeEOS equation-of-state
implementation for stellar interiors (freeeos.sf.net); the Time
Ephemerides project (timeephem.sf.net); PLplot scientific plotting
software package (plplot.sf.net); the libLASi project
(unifont.org/lasi); the Loads of Linux Links project (loll.sf.net);
and the Linux Brochure Project (lbproject.sf.net).
__________________________

Linux-powered Science
__________________________

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