[css3-flexbox] Abspos flex-item positions from Tab Atkins Jr. on 2012-10-17 (www-style@w3.org from October 2012) (original) (raw)
On Tue, Oct 16, 2012 at 5:45 PM, Kang-Hao (Kenny) Lu <kanghaol@oupeng.com> wrote:
(12/08/01 5:50), Tab Atkins Jr. wrote:
Per our action item last week, we've defined the static position of abspos flex items consistently with how they're handled in block and inline flow: http://dev.w3.org/csswg/css3-flexbox/#abspos-items http://lists.w3.org/Archives/Public/www-style/2012Jul/0605.html (minutes)
Sorry for not being able to overcome my slack earlier to review the text, but I find the current prose a bit misleading... I hope my comments below are just editorial.
In the main axis,
1. If there is a subsequent flex item on the same flex line, the
static position is the outer main-start edge of that flex item.
The phrase "on the same flex line" seems to suggest that a 0x0 placeholder goes into the line breaking algorithm and belongs to a line, which slightly contradicts the statement "An absolutely-positioned child element of a flex container does not participate in flex layout beyond the reordering step.". I think it meant to say
| a. If there is no preceding flex item or the preceding flex item | and the subsequent flex item are on the same flex line, ...
2. Otherwise, if there is a preceding flex item on the same flex
line, the static position is the outer main-end edge of that
flex item.
At a minimum, assuming the flex container has at lease one flex item, for an abspos flex-item, if there is no subsequent flex item "on the same flex line", the preceding flex item must be "on the same flex line" because an abspos flex-item can't really occupy a line, unlike a real placeholder. Therefore, "on the same flex line" should be removed from the premise:
| b. Otherwise, if there is a preceding flex item, (that item is on | the same flex line and) the static position ...
3. Otherwise, the static position is determined by the value of
‘justify-content’ on the flex container as if the static
position were represented by a zero-sized flex item.
I suggest s/a/a single/ just so that when there are multiple abspos flex-items, the sentence doesn't read like the more than one 0x0 are being laid out. This is what I suggest:
| c. Otherwise, (there is no flex item in the flex container and) the | static position is determined by the value of ‘justify- | content’ on the flex container as if the static position were | represented by a single zero-sized flex item.
But this order is having a hole in that a flex container having no flex item would be caught by a.'s "if there is no preceding flex item', so this is what I suggest overall (moving c. before. a.):
| 1. If there is no flex item in the flex container, the | static position is determined by the value of ‘justify- | content’ on the flex container as if the static position were | represented by a single zero-sized flex item. | 2. Otherwise, if there is no preceding flex item or the preceding | flex item and the subsequent flex item are on the same flex | line, the static position is the outer main-end edge of the | subsequent flex item. | 3. Otherwise, the static position is the outer main-end edge of | the preceding flex item.
I might go with a different ordering, but I agree with your comments overall. Yes, this is just editorial.
In the cross axis,
1. If there is a preceding flex item, the static position is the
cross-start edge of the flex-line that item is in.
2. Otherwise, the static position is the cross-start edge of the
first flex line.
- should be changed to something like
| 2. Otherwise, the static position is the cross-start edge of the | first flex line or the cross-start edge of the content area if | no flex line exists.
for obvious reasons. I am sure there are other places in the spec that ignore this situation but I don't yet have the chance to do a throughout review.
Even if there are no items, you still have a flex line. It's just empty.
~TJ
Received on Wednesday, 17 October 2012 17:34:29 UTC