Rendering issue with scrollbar in absolute positioning

[jez9999]

Create an absolutely-positioned container element which is a grid with max-height:100%. Have a child element with grid-area: 1/1 and with content that can overflow the container when the viewport gets too short, causing a scrollbar to appear.

Result when content can wrap (content wraps):
https://game-point.net/misc/stickyMaskO ... index6.htm

Result when content can't wrap (horizontal scrollbar is displayed):
https://game-point.net/misc/stickyMaskO ... index7.htm

In both cases, this seems incorrect to me. The browser should calculate the inline content according to the ideal content width, which is the width the content could expand to without taking any soft wrapping opportunities. In the latter case, it's not even expanding the width to fit the minimum content width with the scrollbar despite having plenty of room to do so.

[Moonchild]

This is likely related to Issue #1986 (UXP)