1858360 - Firefox/Safari disagree with Chrome on how to size a grid item with an optional vertical scrollbar

Status: NEW

(Core :: Layout: Grid, task)

Description

[Daniel Holbert [:dholbert]]

Attachment: testcase 1

STR:

1. Configure your OS or browser to always show scrollbars; i.e. to use "traditional" scrollbars rather than overlay scrollbars. (The setting is in system settings on macOS and Windows, and it's in Firefox preferences in Firefox-on-Ubuntu.)
2. Load attached testcase.
3. Resize the window vertically so that the scrollbar appears and disappears in the red area.

Gecko/WebKit behavior: the width of the red area doesn't change when the scrollbar appears/disappears. So, the scrollbar covers up text.

Chromium behavior:

• When the scrollbar appears, it very-briefly covers up text, but then the red area gets wider and it doesn't cover up text. This dynamic statefulness seems to be Chromium-specific.
• ...but if you reload when the scrollbar is visible, then the red area gets skinny again and the scrollbar covers up text (as in Firefox/WebKit).

I plan to file a Chromium bug about this, but I wanted to file a bug in our bug tracker as well since we know of at least one site that sort-of depends on the Chromium behavior (which I'm not sure whether I can mention so I won't at the moment).

Comment 1

[Daniel Holbert [:dholbert]]

Attachment: screencast showing Chrome's instability on this testcase

Here's a screencast showing me slowly resizing a Chrome window that's viewing the attached testcase. You can see that when the scrollbar appears/disappears, there's a single reflow where the layout hasn't updated yet to reflect the scrollbar having appeared/disappeared; and then the next reflow snaps to a wider or skinnier size to reflect the new size.

Later in the screencast, I refresh the page which causes Chrome to layout at the skinnier scrollbar-overlapping-text width (until I resize the window which nudges them to grow that area).

Comment 2

[Daniel Holbert [:dholbert]]

[ni=me to file a Chromium bug on this]

Comment 3

[Daniel Holbert [:dholbert]]

Filed https://bugs.chromium.org/p/chromium/issues/detail?id=1491986

Comment 4

[Daniel Holbert [:dholbert]]

Attachment: screencast showing Chrome having pathological behavior (always using the wrong width) if you go back and forth across the threshold