[Palemoon] Invisible header on websites with many sources

[Karegohan-And-Kamehameha]

As the title says, the header for the uMatrix UI is not displayed correctly on websites with many sources, particularly when the scrollbar appears. The elements of the UI are still clickable and work, but are displayed as a blank bar.
https://i.imgur.com/SlyJqQh.png

Versions:
Palemoon 27.2.0 x64
uMatrix 0.9.3.6

[gorhill]

You have user styles interfering?

[Karegohan-And-Kamehameha]

I just tried turning all userstyles off, it had no effect and the bug still persists.

[gorhill]

I can't reproduce (Pale Moon 27.1.0), you will have to investigate what causes this on your side.

[Karegohan-And-Kamehameha]

I think I figured it out. The issue only occurs when APZ is enabled (setting layers.async-pan-zoom.enabled is set to true).

[gorhill]

I still can't reproduce with layers.async-pan-zoom.enabled set to true.

[Atavic]

Maybe it's related with meta name="viewport" value? Which system is affected?

[Karegohan-And-Kamehameha]

I'm on Windows 7 64bit. I tried forcing D3D9 and OpenGL rendering, both were affected.