Noticed a white border on top of the window with gfx.core-animation.enabled.

MacBook Air (13-inch, Early 2015)
Intel HD Graphics 6000 1536 MB
MacBookAir7,2
Mojave 10.14.5 18F132
Dark Appearance

Firefox theme is "Default".

This happens on 10.14 but not on 10.12. I think they added this effect on 10.14 for "light" windows, and I think 10.14 believes that Firefox is always light, likely because we're not building with the 10.14 SDK (bug 1475652).
I'm going to try to find a workaround for this, but I'm also going to turn on the CoreAnimation preference regardless.

Odd, maybe this is expected for dark mode in Mojave - look at Safari attached.

(In reply to Asif Youssuff from comment #2)

Created attachment 9086563 [details]
Screen Shot 2019-08-19 at 11.42.21 PM.png

Odd, maybe this is expected for dark mode in Mojave - look at Safari attached.

Just wanted to add - the line for dark mode compatible apps is slightly darker. See:

It should be somewhere in the range of #8a8a8a-8c8c8c, but in Firefox it's brighter than #9b9b9b.

Oops, forgot a screenshot: https://i.imgur.com/9RUf6EL.png

According to this reddit thread the border is also visible using the default theme in light mode

This is now present in stable (v70). The workaround is to set "gfx.core-animation.enabled" to false but I guess this has unwanted side effects? It'd be nice to get it fixed.

It's also still present in nightly (v72).

This is screen from MacOS Mojave 10.14.6 in dark mode. In FF before 70 there is no 1px light border line on top, which is much better. Since 70 it is and visually does not look good and bother...

In Firefox Developer Edition (since 70) and latest Nightly there is light 1px border which should not be because it looks bad...

It does appear that somehow the window is being rendered differently, but only on non-retina. Other screenshots here are non-retina as well.

Cropped screenshot of the issue. Visible white line at the top of the window when it is maximized. "Old" refers to Firefox 69, "new" to Firefox 70.

Comparison screenshot - Firefox 69 and Firefox 70. On dark background to show off the white top bar more clearly.

Confirm that setting "gfx.core-animation.enabled" to "false" is a temporary workaround that makes the window look identical to version 69. Whatever the other consequences of that setting are, I don't know.

On macOS HighSierra 10.13.6 if FF70 theme is in dark mode it's OK (as you can see on screen) and there is no 1px light border on top. This is only in Mojave+, regardless of the system's dark theme setting.

Does anyone tested in Catalina?

(In reply to dev-haine from comment #15)

Does anyone tested in Catalina?

Yes, it is happening in Catalina.

The workaround of setting gfx.core-animation.enabled to false no longer works in Firefox 72. The horrible, needless white border is back 😢

Any movement on this? It looks pretty awful at present.

I'm also seeing this in light mode. I can't attach a screenshot but on 74.0.1 on Catalina 10.15.4 I'm still seeing it on light mode.

This is fixed when setting widget.macos.support-dark-appearance to true, bug 1623686. We have switched the default for Nightly and Early Beta (in bug 1715619), so this bug is now fixed in recent Nightlies. We can truly consider this bug fixed once we have enabled the pref on all channels.

Thank you!

This is fixed now that bug 1623686 is resolved.