automatically take screenshots of all skins with a test profile in CI

[mixxxbot]

Reported by: rryan
Date: 2018-11-03T05:39:05Z
Status: Confirmed
Importance: Wishlist
Launchpad Issue: lp1801471

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It would make reviewing skin PRs easier if CI automatically computed screenshots of all the bundled skins. Even better if we had a GitHub bot that commented on the PR with the images embedded.

We'd need a test profile checked into the codebase that the skins could be computed with -- maybe with some fake tracks in the sqlite database. Also, we'd need to avoid any popups that block the boot process (e.g. the soundmanager "no device" warning).

We could try to wire something together with xvfb and a timer, but this will likely hit the launchimage screen sometimes. I'm thinking Mixxx could have a "screenshot" mode where you start it like:

./mixxx --skin LateNight --screenshot LateNight.png --settingsPath ./testProfile

And it starts up, renders the QMainWindow to a png, then shuts down.