Bug 1472272 enables apps other than Firefox to define a dark theme to use when the system appearance changes to dark mode, such as in macOS 10.14+. TB needs to declare the thunderbird-compact-dark theme as the one to use in this situation. Patch coming up.

Once the changes to LightweightThemeManager.jsm from bug 1472272 have been merged to comm-central, this is all that should be needed to enable automatic switching to the dark theme in TB.

Comment on attachment 8989092 [details] [diff] [review] Patch Stephen, once again, many thanks for your help here! I'm moving the review to Richard's queue, it will be easier for him try this out. The change looks very straight forward.

Comment on attachment 8989092 [details] [diff] [review] Patch I have no macOS 10.14 and after bug 1471950 I can't test this on 10.13, so rs=me. When bug 1368808 lands, we can test this on Windows. From me too, Stephen, many thanks for helping us!

Pushed by mozilla@jorgk.com: https://hg.mozilla.org/comm-central/rev/220675514c93 Automatically switch to the dark theme when macOS 10.14+ switches to dark mode. rs=jorgk,Paenglab DONTBUILD