Bug 103672 – Fixed position element in transformed container is not fixed when the container is scrollable

• Status: NEW
• Component: Layout and Rendering

[Xianzhu Wang]

Created attachment 176825 [details]
test case

Fixed position element under a transformed element (which creates a containing block) should be fixed within the containing block.
However, currently, the fixed position element behaves just like an absolute position element. When the containing block is scrollable, the fixed position element will scroll along with other contents.

To reproduce: open the attached test case, try to scroll the green block (a transformed element with overflow: scroll).

Actual result: the yellow block (fixed position element) scrolls in its container.

Expected result: the yellow block should remain fixed within its container (though it can scroll when the whole page is scrolled.)

Created attachment 234188 [details]
More complex test case for fixed-positioned element inside of a scrollable-div inside of a transformed element.

Attaching a test case for a fixed-positioned element inside of a scrollable-dev inside of a transformed element.

Chrome, Firefox, and IE keep the yellow box fixed when the green box is scrolled. I tested Safari 9537.77.4 and WebKit r170147, and both do NOT keep the yellow box fixed.