Should I report this "bug" ?

> ubuntu 12.04
>
> When launching extensions, inkscape is crashing because of python and bad gtktheme.
> (…)
> It looks it's because of some theme that are "buggy".
> After changing theme for human (using gtk-chtheme) inkscape runs fine.

Unfortunately you don't provide any information about where the crash actually occurs (a pastebin with at least the console messages from Inkscape when it crashes, or a gdb backtrace would be helpful).

Questions (due to lack of factual information):
- Which desktop do you use under Ubuntu? e.g. Unity, Gnome, KDE, or Xfce, or some custom window manager?
- Could you share a list of those themes which consistently cause the crash on your system? This would allow to test this on other systems…
- Are all python-based extensions bundled with Inkscape affected, or does this only occur when running externally developed and maintained extensions which open a custom dialog (using pygtk) - for example 'textex' and 'sozi'?
- Caveat: Inkscape 0.48.3.1 has a well-known regression wrt to extensions which cause Inkscape to crash when executing any extension with certain files. Could you please test whether the crash you are experiencing isn't actually triggered by bug #944077 [1] (instead of buggy gtk themes)?

---
[1] Known regression in Inkscape 0.48.3.1 causing Inkscape to crash with certain files:
Bug #944077 “inkscape crashed with SIGSEGV in Inkscape::Extension::Implementation::Script::effect()”
<https://bugs.launchpad.net/inkscape/+bug/944077>

Workaround for affected files:
<https://bugs.launchpad.net/ubuntu/+source/inkscape/+bug/944077/comments/11>

it looks like its gtk2-engines-oxygen that is faulty
-------------------------------------------------------------------

echo $DESKTOP_SESSION
= gnome-shell

sudo apt-get install gtk2-engines-oxygen gtk3-engines-oxygen oxygen-icon-theme-complete

gtk-chtheme ; <= choose oxygen-gtk

// as soon as you apply you should see n lines
// (gtk-chtheme:4682): Gtk-CRITICAL **: IA__gtk_settings_set_string_property: assertion `GTK_SETTINGS (settings)' failed

inkscape

create a rect;
apply extensions/color/random => ok.

run custom personal filter
the filter runs but there's a warning popup with

(style_dropshadow.py:4795): Gtk-CRITICAL **: IA__gtk_settings_set_long_property: assertion `GTK_SETTINGS (settings)' failed

(style_dropshadow.py:4795): Gtk-CRITICAL **: IA__gtk_settings_set_long_property: assertion `GTK_SETTINGS (settings)' failed

(style_dropshadow.py:4795): Gtk-CRITICAL **: IA__gtk_settings_set_long_property: assertion `GTK_SETTINGS (settings)' failed

(style_dropshadow.py:4795): Gtk-CRITICAL **: IA__gtk_settings_set_long_property: assertion `GTK_SETTINGS (settings)' failed

(style_dropshadow.py:4795): Gtk-CRITICAL **: IA__gtk_icon_theme_get_for_screen: assertion `GDK_IS_SCREEN (screen)' failed

(style_dropshadow.py:4795): Gtk-CRITICAL **: IA__gtk_icon_theme_get_for_screen: assertion `GDK_IS_SCREEN (screen)' failed

(style_dropshadow.py:4795): Gtk-CRITICAL **: IA__gtk_icon_theme_prepend_search_path: assertion `GTK_IS_ICON_THEME (icon_theme)' failed

(style_dropshadow.py:4795): Gtk-CRITICAL **: IA__gtk_icon_theme_get_for_screen: assertion `GDK_IS_SCREEN (screen)' failed

(style_dropshadow.py:4795): Gtk-CRITICAL **: IA__gtk_icon_theme_prepend_search_path: assertion `GTK_IS_ICON_THEME (icon_theme)' failed

(style_dropshadow.py:4795): Gtk-CRITICAL **: IA__gtk_settings_set_string_property: assertion `GTK_SETTINGS (settings)' failed

(style_dropshadow.py:4795): Gtk-CRITICAL **: IA__gtk_settings_set_string_property: assertion `GTK_SETTINGS (settings)' failed

(style_dropshadow.py:4795): Gtk-CRITICAL **: IA__gtk_settings_set_string_property: assertion `GTK_SETTINGS (settings)' failed

note: I can't reproduce but for some time I got a lot of crash when running "any" exensions.
      Now it's only my custom extensions that are displaying a popup.

gtk-chtheme ; <= choose human

inkscape

the bug is still there !

sudo rm /usr/share/themes/oxygen-gtk/gtk-2.0/gtkrc

gtk-chtheme ; <= choose human again

inkscape

the bug is gone.

Ubuntu 0.48.3.1 r9886

> Ubuntu 0.48.3.1 r9886

I meant ubuntu 12.04, inkscape 0.48.3.1 r9886

> = gnome-shell
>
> sudo apt-get install gtk2-engines-oxygen gtk3-engines-oxygen oxygen-icon-theme-complete
> gtk-chtheme ; <= choose oxygen-gtk
> inkscape
> (…)
> note: I can't reproduce but for some time I got a lot of crash when running "any" exensions.

Those crashes very likely were due to bug #944077 - the details are in the comments of the report, if you are curious what triggers it, as well as steps how to prevent it with affected files.

> Now it's only my custom extensions that are displaying a popup.

Obviously you need to file a report against your custom extension in this case ;-) Since I don't know specifics about the custom extension, you have to figure that out yourself (do you open a custom dialog using pygtk from 'style_dropshadow.py' which I assume is the script of your custom extension?). To me the remaining issue (critical but not fatal warnings from GTK+) looks either like a compatibility issue between pygtk (or gtk2 apps in general) with the gtk2 theme engine of gtk-oxygen (from KDE), or like a partially broken local installation of GTK+/Gnome and/or KDE (you don't mention KDE, but I assume that you use (or used to use) it since gtk2-engines-oxygen are intended to provide "visual consistency between GTK+ and Qt-based applications running under KDE.").

> gtk-chtheme ; <= choose human
> inkscape
> the bug is still there !
> sudo rm /usr/share/themes/oxygen-gtk/gtk-2.0/gtkrc
> gtk-chtheme ; <= choose human again
> inkscape
> the bug is gone.

Maybe this topic (random Google search result based on the Gtk-CRITICAL messages) helps:
<https://bbs.archlinux.org/viewtopic.php?pid=999078#p999078>
(I would recommend to first check your personal configuration files (e.g. ~/.gtkrc-2.0, or possibly ~/.gtkrc-2.0.mine) before starting to delete system files which are managed by apt-get, or use toolkit-/desktop-specific settings tools to change theme/icon-theme related settings).

Summary:
Based on the information in your second comment, and web search results for the Gtk-CRITICAL messages, ISTM that this is not an inkscape-related issue (let alone bug) - either the gtk-oxygen-based theme engine/widgets themselves need another update, or the desktop settings for KDE and Gnome somehow interfere / are partially out-of-sync (or misconfigured).

Upstream gtk2-engine-oxygen bug tracker:
<https://bugs.kde.org/buglist.cgi?product=Oxygen&component=gtk2-engine&resolution=--->