2021168 - Consider having 'overflow:visible' compute to 'auto' on <textarea>, for compatibility with Chromium & WebKit

Status: NEW

(Core :: Layout: Form Controls, defect)

Description

[Daniel Holbert [:dholbert]]

STR:

1. Load https://bug984275.bmoattachments.org/attachment.cgi?id=8392082
2. Inspect the "textarea's overflow property" section of the testcase.

Or more generally, just use DevTools to inspect the computed value of the overflow property, on a <textarea> or even <textarea style="overflow:visible">.

FIREFOX RESULTS:
In Firefox, the computed value of overflow is whatever was specified (and defaults to visible if there's no specified value).

CHROME/WEBKIT RESULTS:
In Chrome/WebKit, the computed value of overflow is auto if you manually specified visible; and auto also is the default if you don't specify overflow at all. (The initial value of overflow is visible, but Chromium/WebKit convert that to auto at computed-value time on these elements.)

The Chrome/WebKit behavior kinda makes sense, because visible does actually behave as auto on a textarea (we don't literally let the contents leak out into the page and overflow the bounds of the textarea). So maybe it'd be good to align on that, as a way of explaining this textarea behavior?

Historical note, this was sort-of originally filed as bug 984275 (that bug was also asking for this property's computed value to magically depend on whether-or-not-the-contents-actually-overflow, which was apparently what IE/WebKit did at the time; but I think no browser does that these days. Bug 984275 comment 1 mentioned the difference between Gecko and Chrome which is what I've encapsulated in this bug here.)

Comment 1

[Daniel Holbert [:dholbert]]

(bug 2021158 is related here, in that it's about a particular behavior that depends on the computed overflow value.)