[csswg-drafts] [css-overflow] handling of negative scrollable overflow region is incorrect (#9457)

dbaron has just created a new issue for https://github.com/w3c/csswg-drafts:

== [css-overflow] handling of negative scrollable overflow region is incorrect ==
This [testcase](https://software.hixie.ch/utilities/js/live-dom-viewer/?%3C!DOCTYPE%20html%3E%0A%3Cdiv%20style%3D%22overflow%3A%20scroll%3B%20width%3A%20100px%3B%20height%3A%20100px%22%3E%0A%20%20%3Cdiv%20style%3D%22width%3A%2010px%3B%20height%3A%2010px%3B%20margin-top%3A%20-30px%3B%20margin-left%3A%20-30px%22%3E%0A%20%20%20%20%3Cdiv%20style%3D%22width%3A%20200px%3B%20height%3A%20200px%3B%20background%3A%20aqua%22%3E%3C%2Fdiv%3E%0A%20%20%3C%2Fdiv%3E%0A%3C%2Fdiv%3E) shows that the handling of the "negative scrollable overflow region" in the [rules for computing scrollable overflow](https://drafts.csswg.org/css-overflow-3/#scrollable) is interoperably a different behavior from the one the spec describes.

The spec describes that the union used to compute the scrollable area ignores boxes whose *border box* is entirely within the negative scrollable overflow region.  However, the area that matters should be the scrollable overflow of the box (when applied), not the border box.

According to the spec the above testcase should not be scrollable, but it is interoperably scrollable across Chrome, Firefox, and Safari.

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/9457 using your GitHub account


-- 
Sent via github-notify-ml as configured in https://github.com/w3c/github-notify-ml-config

Received on Wednesday, 11 October 2023 19:04:43 UTC