Bug 225809 – [LFC][IFC] line-height incorrectly triggers scrollable overflow

• Component: Layout and Rendering
• Status: NEW

[alan]

Created attachment 428623 [details]
test case

ssia

[Radar WebKit Bug Importer]

<rdar://problem/78017815>

[Radar WebKit Bug Importer]

<rdar://problem/78017824>

[alan]

see http://wpt.live/css/CSS2/linebox/scrollable-overflow.tentative.html

[alan]

According to the CSS Overflow Module Level 3 (https://www.w3.org/TR/css-overflow-3/#scrollable) and CSS Inline Layout Module Level 3 (https://www.w3.org/TR/css-inline-3/#line-layout) this looks like a progression.

CSS Overflow Module says:
"...
The scrollable overflow area is the union of:
...
 - all line boxes directly contained by the box
.."

while CSS Inline Layout Module says:

"..
The line box’s logical height is calculated to exactly include the aligned layout bounds of all its inline-level boxes.
.."

where the layout bounds are computed by taking the (non-normal) line-height into account ("When its computed line-height is not normal, its layout bounds are derived solely from metrics of its first available font (ignoring glyphs from other fonts), and leading is used to adjust the effective A and D to add up to the used line-height."

so it looks like the "line-height" here should affect the scrollable overflow area and Safari should produce a scrollbar for it.

It also matches Firefox(88.0.1) behavior. I'd say this is a progression but according to https://bugs.chromium.org/p/chromium/issues/detail?id=996847, this is not what's expected.

[alan]

Blink's test reduction

https://bugs.chromium.org/p/chromium/issues/attachmentText?aid=409419