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

Hello,

Here is a tested patch for this report, as a Debian patch applied after fix-version.patch.
It loads libnggui.so.6.2 first and falls back to the unversioned name, in ng/ng.tcl and in the pre-generated ng/onetcl.cpp, as the report describes.

Tested in a clean debian:testing container without libnglib-dev.
With 6.2.2606+dfsg1-1, `netgen -batchmode` stops at "couldn't load file libnggui.so".
With the patch it loads the GUI library and reaches "This operation needs a mesh", the same as with libnglib-dev installed.
Started from the desktop menu, the patched package opens Netgen's window.
The version in the load line follows the SOVERSION set in fix-version.patch, so the two change together.

Description: Load the GUI library by its SONAME
 fix-version.patch gives libnggui the SONAME libnggui.so.6.2, and the
 unversioned libnggui.so link is shipped only in libnglib-dev, so the Tcl
 script's "load libnggui.so gui" failed whenever libnglib-dev was not
 installed: the GUI started from the menu printed "couldn't load file
 libnggui.so" and exited.  Load the library by its SONAME, and keep the
 unversioned name as the fallback for builds without fix-version.patch.
 The version here follows the SOVERSION set in fix-version.patch.
Author: Daniel Ramos (Capitain Jack) <Capitain_Jack@yahoo.com>
Assisted-by: Claude Opus via Claude Code
Forwarded: not-needed
Last-Update: 2026-10-10
--- a/ng/ng.tcl
+++ b/ng/ng.tcl
@@ -2,7 +2,9 @@
 catch {lappend auto_path $env(NETGENDIR)/../lib }

 if {[catch {Ng_GetCommandLineParameter batchmode} result ]} {
-	load libnggui[info sharedlibextension] gui
+	if {[catch {load libnggui[info sharedlibextension].6.2 gui}]} {
+		load libnggui[info sharedlibextension] gui
+	}
 }

 set batchmode [Ng_GetCommandLineParameter batchmode]
--- a/ng/onetcl.cpp
+++ b/ng/onetcl.cpp
@@ -3,8 +3,10 @@
 ,"catch {lappend auto_path $env(NETGENDIR) }\n"
 ,"catch {lappend auto_path $env(NETGENDIR)/../lib }\n"
 ,"if {[catch {Ng_GetCommandLineParameter batchmode} result ]} {\n"
+,"if {[catch {load libnggui[info sharedlibextension].6.2 gui}]} {\n"
 ,"load libnggui[info sharedlibextension] gui\n"
 ,"}\n"
+,"}\n"
 ,"set batchmode [Ng_GetCommandLineParameter batchmode]\n"
 ,"if {$batchmode==\"undefined\"} {\n"
 ,"if {[catch {package require tkdnd } result ]} {\n"

This patch was prepared with AI assistance; I directed and tested it.

Daniel Ramos

We believe that the bug you reported is fixed in the latest version of
netgen, which is due to be installed in the Debian FTP archive.

A summary of the changes between this version and the previous one is
attached.

Thank you for reporting the bug, which will now be closed.  If you
have further comments please address them to 1150173@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.

Debian distribution maintenance software
pp.
Drew Parsons <dparsons@debian.org> (supplier of updated netgen package)

(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing ftpmaster@ftp-master.debian.org)
Format: 1.8
Date: Sat, 17 Oct 2026 17:54:58 +0200
Source: netgen
Architecture: source
Version: 6.2.2606+dfsg1-3
Distribution: unstable
Urgency: medium
Maintainer: Debian Science Maintainers <debian-science-maintainers@lists.alioth.debian.org>
Changed-By: Drew Parsons <dparsons@debian.org>
Closes: 1125008 1150068 1150173
Changes:
 netgen (6.2.2606+dfsg1-3) unstable; urgency=medium
 .
   * Team upload.
   * debian/tests Depends: dpkg-dev (for dpkg-architecture). Closes: #1150068
   * netgen Depends: libnglib-dev instead of libnglib-6.2t64
     (>= ${binary:Version}). Tcl is not smart about shared libraries,
     treating "libnglib.so" literally, and is ignorant of the ABI.
     Closes: #1150173, #1125008.
   * move debian/menu to netgen.menu
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