[snap] At first run on bionic, keyboard input is delayed by more than 10 seconds (by fontconfig cache generation)

[Olivier Tilloy]

This seems to happen only the first time the chromium snap is run after installing it afresh (not after upgrading).

Steps to reproduce:

 1) $ snap remove chromium # in case it was already installed
 2) $ snap install chromium
 3) $ snap run chromium
 4) wait for the welcome page to be fully loaded, then press Ctrl+L to focus the omnibox (aka address bar)

Expected result: the omnibox is instantly focused and its text is selected, key strokes are registered and input into it

Current result: there's a long delay before the omnibox is actually focused and its text selected, more than 10 seconds.

[Olivier Tilloy (osomon)]

It's not just the omnibox that's unresponsive for some time at startup. It appears that anything that involves keyboard input is delayed, e.g. opening the task manager with Shift+ESC, or opening a new tab with Ctrl+T (however opening a new tab by clicking on the button to the right of the first tab is instantaneous, but then pressing a key to start typing in the omnibox lags by the same delay).

[Olivier Tilloy (osomon)]

Interestingly, I can observe this only on bionic (18.04). I’ve tested the chromium snap in VMs running trusty, xenial, artful and bionic, and only bionic appears to be affected.

[Olivier Tilloy (osomon)]

I'm pretty sure that this issue started happening at some point during the bionic development cycle (I was dist-upgrading daily), so this is definitely something in the bionic stack that's triggering the issue.

[Olivier Tilloy (osomon)]

I can reliably reproduce between each run if I delete ~/snap/chromium/common/.cache/fontconfig

[Olivier Tilloy (osomon)]

James identified the issue, which potentially affects all snaps, not just chromium: https://forum.snapcraft.io/t/snaps-are-still-slow-to-launch-on-first-time-launch/6888/5.

[Olivier Tilloy (osomon)]

This was fixed in snapd 2.36.2 (see https://forum.snapcraft.io/t/2-36-point-releases/9008 and https://github.com/snapcore/snapd/releases/tag/2.36.2).