Calibre segfaults on startup

[dbart]

I run Calibre on Ubuntu 14.04 with the Mate desktop environment.

After the latest update, Calibre is refusing to start and eventually segfaults or I kill it. Prior to the segfault the entire screen flashes several times, like Calibre is trying to create a window over and over and over again, but can't. The flashes are full screen and totally prevent me from doing anything until it either segfaults or I ssh in from my phone and issue a `killall calibre`.

My guess is that something was upgraded on my system that is causing the error, but I don't know what. I generally never restart calibre unless there's an update for it, and it was after the update to 2.21 that I noticed the error.

I launched calibre in a terminal to see what was happening and there are a lot of errors, but I'm not sure which are the real ones and what are red herrings.

On the command-line I first see:

GLib-GIO-Message: Using the 'memory' GSettings backend.  Your settings will not be saved or shared with other applications.

(calibre:29952): Gtk-CRITICAL **: IA__gtk_widget_style_get: assertion 'GTK_IS_WIDGET (widget)' failed

(calibre:29952): Gtk-CRITICAL **: IA__gtk_widget_style_get: assertion 'GTK_IS_WIDGET (widget)' failed

(calibre:29952): Gtk-CRITICAL **: IA__gtk_widget_style_get: assertion 'GTK_IS_WIDGET (widget)' failed

(calibre:29952): Gtk-CRITICAL **: IA__gtk_widget_style_get: assertion 'GTK_IS_WIDGET (widget)' failed
Traceback (most recent call last):
  File "site-packages/calibre/gui2/ui.py", line 151, in __init__
  File "site-packages/calibre/gui2/ui.py", line 165, in init_iaction
  File "site-packages/calibre/customize/__init__.py", line 582, in load_actual_plugin
  File "importlib/__init__.py", line 37, in import_module
  File "site-packages/calibre/customize/zipplugin.py", line 179, in load_module
  File "calibre_plugins.apnx_generator.apnxaction", line 14, in <module>
ImportError: No module named PyQt4.Qt

Then there are a ton of:

(calibre:29952): Gtk-CRITICAL **: IA__gtk_widget_style_get: assertion 'GTK_IS_WIDGET (widget)' failed

And also several messages like these:

QWidget::paintEngine: Should no longer be called
QPainter::begin: Paint device returned engine == 0, type: 1
QPainter::setRenderHint: Painter must be active to set rendering hints
QPainter::pen: Painter not active
QPainter::setPen: Painter not active
QPainter::drawRects: Painter not active

And even a:

(calibre:29952): Gtk-CRITICAL **: IA__gtk_widget_style_get: assertion 'GTK_IS_WIDGET (widget)' failed
QWidget::setMinimumSize: (MainWindow/Main) The largest allowed size is (16777215,16777215)

I've tried starting with --ignore-plugins but the behavior is the same.

I also tried downgrading to old versions using the instructions on http://calibre-ebook.com/download_linux but old versions (2.20, 2.19, 2.18) behave the same (which is why I'm thinking it was a system update that caused it).

Any ideas? Thanks in advance.

[eschwartz]

When you say you restarted with --ignore-plugins... you mean, you still get errors about the outdated plugin?

Which messages still appear when you use --ignore-plugins?

[kovidgoyal]

Try getting a stack trace with gdb, although since the binary has its symbols stripped, it might not be very useful.

From your description it looks like the Qt theme plugin on your system is incompatible with the version of Qt bundled with calibre, causing the crash. You can get calibre to not use the system theme plugin, edit ~/.config/calibre/gui.json and change 'ui_style' to 'calibre' from 'system'

[dbart]

Originally Posted by kovidgoyal

From your description it looks like the Qt theme plugin on your system is incompatible with the version of Qt bundled with calibre, causing the crash. You can get calibre to not use the system theme plugin, edit ~/.config/calibre/gui.json and change 'ui_style' to 'calibre' from 'system'

That was it!

Once I changed the 'ui_style' to 'calibre' things are working again. Thanks!

[jeffrx]

I have the same exact system (Ubuntu MATE 14.04) but when I try to edit '~/.config/calibre/gui.json' there is no 'ui_style' to change. Am I missing something? I pull it up in gedit as root and I have searched several times but it is not listed.

[kovidgoyal]

Run this command in a terminal and it will set it for you:

calibre-debug -c "from calibre.gui2 import gprefs; gprefs['ui_style'] = 'calibre'"

[eschwartz]

Um, isn't the fix already in the latest production release?

Just set the env var "CALIBRE_IGNORE_SYSTEM_THEME" to 1 and then you can start calibre and set it the usual way.

[kovidgoyal]

Yes, but I dont know what version of calibre the OP is running, since he didn't say. So I posted a solution that is version independent.

[jeffrx]

Thank you! That did it. FWIW, Ubuntu MATE seems to have issues with Gtk across the board. Still my favorite DE though. The kinks will work our eventually.