- From: Tab Atkins Jr. <jackalmage@gmail.com>
- Date: Wed, 1 Jul 2015 11:22:34 -0700
- To: Florian Rivoal <florian@rivoal.net>
- Cc: www-style list <www-style@w3.org>
On Wed, Jul 1, 2015 at 8:08 AM, Florian Rivoal <florian@rivoal.net> wrote: > The current definition of the 'contain' property doesn't work well > with regions. flow-from and flow-into are scoped to the contain:style > container, but that's not enough, and regions make contain:layout > ineffective when used without contain:style. > > <article> > <div id=container> > <p>Lorem ipsum dolor sit amet... > </div> > <div id=container> > <div>...<table>...<tr>...<td>.../* arbitary nesting */ > <p>Aenean vestibulum, dui eu bibendum sagittis... > </td>...</tr>...</table>...</div> > </div> > <p>Sed semper vehicula nisl ac dignissim... > </article> > > <style> > container { > contain:layout; > height: 100px; > width: 100px; > } > p { flow-into: my-flow; } > p { flow-from: my-flow; } > </style> > > You can't know what the content of the second or third <p> > is going to be (and therefore you cannot lay them out) > without first laying out the content of the preceding > container. Which also means you cannot figure out the > height of <article>, without doing a full layout of all > its children, despite the presence of contain:layout on > some of them. > > In the best case, that means that UAs cannot do the type of > optimizations you'd expect from contain:layout if regions > are involved, and in the worst case, that means UAs can > never to the type of optimization you'd expect from > contain:layout because regions *might* be involved, and > it's too hard to figure out if they actually are. > > I see 2 ways out of that: > > 1) merge layout and style containment > > 2) add a region-specific rule to layout containment in addition > to those in style containment. Here's one that should work: > > The first (if any) region in a region chain that is either > a contain:layout element itself or the descendant of one is > treated as if it was the last region in the chain, and gets > all the remaining content in the associated named flow. > Subsequent regions in the chain do not receive any content > from the named flow. > > You'll still need to walk the through the preceding regions > in a region chain before you can layout the next one, but > if any of them is in a contain:layout element, you don't need > to lay it out before you can continue. > > Actually, we need to reword that so that if several regions > of the same chain are descendants of the same contain:layout > element, it's the last of one rather than the first, that should > behave as the last one in the chain. But that's hard to phase well, > so it's probably easier to understand my point with the definition > above, even if we need to tweak it before putting it in the spec. I'm fine with layout containment also breaking region chains. ~TJ
Received on Wednesday, 1 July 2015 18:23:20 UTC