GNOME shell crashes when dash-to-dock extension is disabled in overview

[taoky]

With current code from master (1053b3e), dash-to-dock would make shell crash in both GNOME 45 and 46. This could be reproduced by:

1. Open Overview (both window picker and app grid could trigger this)
2. Lock the screen, or run gnome-extensions disable [email protected] if sshing.

My local bisecting result shows that de35ab6 is the first bad commit (weird) when testing with GNOME 45. And this diff patch "workarounds" the crash in both GNOME 45 and 46:

diff --git a/_stylesheet.scss b/_stylesheet.scss
index b23cc43..adc45af 100644
--- a/_stylesheet.scss
+++ b/_stylesheet.scss
@@ -251,10 +251,6 @@ $dock_style_modes: [null, shrink, extended, extended-shrink];
     }
 }
 
-.dash-item-container .overview-tile .overview-icon,
-.dash-item-container .show-apps .overview-icon {
-    background-color: rgba(255,255,255,0);
-}
 
 .dash-item-container .overview-tile:hover .overview-icon,
 .dash-item-container .overview-tile.focused .overview-icon,

This issue looks like https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/7339 but it's slightly different (crashing widget is Gjs_ui_dash_ShowAppsIcon), and I have tried to find the cause but no clue. And this bug, if exists in shell, could only be triggered by an extension. I have also tried to build a simpler extension example, but it does not crash with a CSS-only extension.

bt full (GNOME 46):
bt-full-fedora-gnome46.txt

[vanvugt]

Thanks for the bug report. dash-to-dock shouldn't be able to cause a segfault like that, and particularly not with style changes. It looks like we should track this upstream just keeping in mind the only way to reproduce it is with dash-to-dock.

[vanvugt]

I'm working on an upstream fix so let's track this in https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/7339 instead.

[vanvugt]

The upstream fix is https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/3252, and it's already fixed in Ubuntu.

[nleanba]

Even if this gets fixed in upstream GNOME, it would be nice if you could update the extension to not have the problematic CSS rule -- it might take a while until GNOME is patched and the update reaches e.g. my laptop.

While I agree that this is not "your" bug, but an upstream bug, I still think it would be best to implement a workaround here. I would like to be able to use the extension again before GNOME 49 or even 50 gets released with the fix.

[bradchristensen]

In the meantime, you can manually apply the patch mentioned by @taoky on your system by modifying ~/.local/share/gnome-shell/extensions/dash-to-dock@[email protected]/stylesheet.css (it's the first few lines at the top of the file), bearing in mind that it might get overwritten if the extension updates itself. For me it seems to make no difference to the dock appearance.

[vanvugt]

Since @sergio-costas wrote the "first bad commit" de35ab6 he can decide whether modifying that is an acceptable workaround for non-Ubuntu systems. But I suspect it may not even be a reliable workaround if any stylesheet changes could cause the same crash.

[sergio-costas]

I'm not sure... I tested it in Gnome Shell 47 and seems to have no aesthetic impact, but as @vanvugt said, that's not even a reliable workaround because the bug is in Gnome Shell, so a future patch in dash-to-dock can easily reinsert it...

[vanvugt]

I guess there's a stochastic benefit to changing the CSS. If it reduces the frequency of the crashes then that reduces the burden of repeated crash reports we get here.

[sergio-costas]

You are right... I'll prepare a quick patch and do more tests.

[sergio-costas]

@vanvugt @bradchristensen I'm unable to reproduce the bug neither with the dash-to-dock from the extensions page, nor with the code from master. I've been doing the tests in a VM with Fedora 40 (Gnome Shell 46).