- From: Dirk Schulze <dschulze@adobe.com>
- Date: Fri, 20 Sep 2013 13:02:01 -0700
- To: "intelligentdesigner@timgallantcreative.com" <intelligentdesigner@timgallantcreative.com>
- CC: "Tab Atkins Jr." <jackalmage@gmail.com>, www-style list <www-style@w3.org>
On Sep 20, 2013, at 9:40 PM, intelligentdesigner@timgallantcreative.com wrote: > Could you clarify what this accomplishes beyond the existing CSS clip > property? clip does just work with absolute positioned elements. You may can use clip-path and implementations could optimize for that. But a new keyword for overflow might be adapted a lot easier by web developers (and is less code and less complexity for authors and UAs). Greetings, Dirk > > Tim Gallant > > -----Original Message----- > From: Tab Atkins Jr. > Sent: Friday, September 20, 2013 2:03 PM > To: www-style list > Subject: Fwd: Proposal for "overflow:clip" for stronger painting isolation > > I've been talking with out layout/compositor people here on Blink for > a while now, and one of the things that has shaken out as a big helper > in getting things to work *fast* is having strong, guaranteed methods > to isolate parts of the page. > > In particular, isolating the painting of an element seems like a big > win - having some way to guarantee that the element can be > hard-clipped to its boundary without losing anything important. > overflow:hidden doesn't *quite* do this - abspos and fixpos elements > can escape the bounds of the element. > > As well, overflow:hidden still allows scrolling into the hidden area, > through JS. This isn't an edge-case - this technique is used by a lot > of JS libraries. This means that we can't depend on the element only > painting its visible area - we have to speculatively paint further, so > we can scroll smoothly at a moment's notice. > > To get around both of these issues and provide stronger optimization > guarantees to the browser, I suggest we add a "clip" or "contained" > value to overflow. This does a strong clipping - nothing inside the > element can paint outside the element's rect. > > It also acts as a positioning root for abspos inside the element, and > kills fixpos, reverting it to abspos with the element as its > positioning root. > > The value also completely prevents scrolling - the scrollWidth/Height > of the element is its visible width/height. > > Thoughts? > > ~TJ > > >
Received on Friday, 20 September 2013 20:02:28 UTC