v153 · single-axis scroll containers
What each pair computes to
The specified value and the computed value are not the same thing, and for overflow they diverge in ways that decide whether an axis is a scroll container. Every pair is measured here in a real element — including whether the axis actually scrolls, tested by scrolling it.
Every pair, measured
| specified | computed x | computed y | x scrolls? | y scrolls? | what happened |
|---|
"Scrolls?" is not read from the computed style. Each row gets a real element with oversized content, has scrollLeft and scrollTop set to 50, and is asked what they are afterwards. An axis that keeps the offset is a scrollport whatever its scrollbar looks like.
The highlighted pair, at size
The sample is focusable so it can be scrolled from the keyboard: with the box focused, arrow keys move whichever axis is a real scrollport. That is the difference this feature is about, and it is easier to feel than to read.