When moving my nightly window between different DPI monitors (using Wayland), the low DPI monitor shows things as if they're doubled in size.

I've just installed Ubuntu 15.10 on my machine and I'm seeing the same behavior (on X11). Nightly is better than release, but still too big (the other GNOME applications are scaled correctly).

(In reply to Marco Castelluccio [:marco] from comment #1) > Nightly is better than release, but still too big (the other GNOME > applications are scaled correctly). Forget it, they're the same. It also happens if I only open Firefox in the low DPI monitor.

Filed bug 1228570 for the non-Wayland case.

Using the org.mozilla.FirefoxNightlyWayland flatpak, Firefox does react to being placed on a hidpi monitor when coming from a lowdpi one. Some things are done properly: - Everything correctly gets rendered to 2× the size when the output specifies a scale of 2. - The decorations correctly specify they are drawn at scale 2, and thus the compositor doesn’t touch them on the hidpi output (it does downscale them on the lowdpi monitor, to avoid it being huge). But there are many things still wrong: - When a hidpi output exists, fonts are rendered huge instead of the usual size. - The chrome + content subsurface doesn’t specify its scale, so it is upscaled 2× for a total of 4× on the hidpi output, and doesn’t get downscaled on the lowdpi one, making it appear 2× as wide/high as its decorations. - Input happens at the wrong place, this is likely going to be fixed alongside the previous point. Note that all this is on pure Wayland, X11 Firefox doesn’t do anything different than usual when there is a hidpi output present.