parent & child with position fixed, parent overflow:hidden bug

Question

I don't know if there is an issue, but I was wondering why the overflow:hidden does not function on fixed parent/children element.

Here's an example:

CSS and HTML:

Live demo: jsFiddle

Answer 1

You could consider using CSS clip: rect(top, right, bottom, left); to clip a fixed positioned element to a parent. See demo at http://jsfiddle.net/lmeurs/jf3t0fmf/.

Beware, use with care!

Though the clip style is widely supported, main disadvantages are that:

1. The parent's position cannot be static or relative (one can use an absolutely positioned parent inside a relatively positioned container);
2. The rect coordinates do not support percentages, though the auto value equals 100%, ie. clip: rect(auto, auto, auto, auto);;
3. Possibillities with child elements are limited in at least IE11 & Chrome34, ie. we cannot set the position of child elements to relative or absolute or use CSS3 transform like scale.

See http://tympanus.net/codrops/2013/01/16/understanding-the-css-clip-property/ for more info.

EDIT: Chrome seems to handle positioning of and CSS3 transforms on child elements a lot better when applying backface-visibility, so just to be sure we added:

-webkit-backface-visibility: hidden;
-moz-backface-visibility: hidden;
backface-visibility: hidden;

to the main child element.

Also note that it's not fully supported by older / mobile browsers or it might take some extra effort. See our implementation for the menu at bellafuchsia.com.

1. IE8 shows the menu well, but menu links are not clickable;
2. IE9 does not show the menu under the fold;
3. iOS Safari <5 does not show the menu well;
4. iOS Safari 5+ repaints the clipped content on scroll after scrolling;
5. FF (at least 13+), IE10+, Chrome and Chrome for Android seem to play nice.

EDIT 2014-11-02: Demo URL has been updated.