Bug#1150173: netgen: GUI does not start without libnglib-dev: loads the unversioned libnggui.so

[Daniel Ramos]

Package: netgen
Version: 6.2.2606+dfsg1-1
Severity: important

Dear Maintainer,

With only netgen installed, the graphical interface does not start:

  $ netgen
  NETGEN-6.2.2606
  ...
  Error in Tcl-Script:
  result = couldn't load file "libnggui.so": libnggui.so: cannot open shared object file: No such file or directory

ng/ng.tcl loads the GUI library by its unversioned name:

  load libnggui[info sharedlibextension] gui

In the Debian packaging that name exists only in libnglib-dev
(debian/libnglib-dev.install: usr/lib/*/libnggui.so), while the runtime
package libnglib-6.2t64 ships libnggui.so.6.2 and libnggui.so.6.2.2606.
Installing libnglib-dev makes the GUI start, which is why it is easy to
miss on a development machine.

A possible correction is a Debian patch that loads the library by its
SONAME, so no -dev symlink is needed at run time:

  -	load libnggui[info sharedlibextension] gui
  +	load libnggui[info sharedlibextension].6.2 gui

Note that the netgen binary does not read ng/ng.tcl at run time: the Tcl
sources are compiled into ng/onetcl.cpp, which is committed pre-generated
in the source tree. The same change has to be made in ng/onetcl.cpp (or
onetcl.cpp regenerated during the build), otherwise the patch has no effect.

Steps to reproduce, in a clean debian:testing container:
  apt-get install netgen xvfb xauth
  xvfb-run -a netgen

Found while packaging a stereo 3D version of netgen for Sparky Stereo OS,
an edition of SparkyLinux.

Regards,
Daniel Campos Ramos