STR:

1. Start with GDK_BACKEND=wayland on Ubuntu 18.10.
2. Set privacy.resistFingerprinting = true.
3. Maximize window.
4. Restart firefox.

Window should be non-maximized and reduced in size like with XWayland due to resist fingerprinting rounding down window dimensions but instead it remains full size (but not maximized). Only the first window is affected, other maximized windows in the session get rounded correctly.

How do you restart the browser? Just quit + start gives me non-maximized browser on Fedora 30 / latest nightly. Thanks.

Try it with two maximized windows in the session, after quitting with Ctrl+Q and resuming the previous session, both windows should be the exact same size but with Wayland backend the first window is the wrong size.

I can no longer reproduce this in latest Nightly.

Fix window:
https://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=9d74f5279e4f223d07fdfddbbe2340f39c6f7a53&tochange=58dd38390b0664680e5ad0307faec3923abf560d

Fixed by Bug 1525762.

This behavior has returned.

Regression window:
https://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=a896b1f02e484a40f130ddea76cba03051c46341&tochange=ff6b2d1aff7a8e1bd32b6c7134fdf4704c57034d

Regressed by Bug 1540856.

Presumably this has something to do with the early blank window paint code. Bug 1540856 just fixed a regression that briefly disabled that code. It didn't cause this.

(In reply to Kris Maglione [:kmag] from comment #5)

Presumably this has something to do with the early blank window paint code.

Yes, it does not happen with browser.startup.blankWindow = false.

I cannot reproduce this since upgrading to Ubuntu 19.10 with Nightly builds after the regression, it appears to have been fixed upstream.