[css-align] Which behavior for block's "justify-self: center"?

[tabatkins]

There are two possible behaviors for justify-self:center on blocks in the presence of a float:

1. Reduce the size of the alignment container by the size of the float's margin box, then center the block in the remaining space (this is the behavior of HTML's align attribute)
2. Center the block ignoring the float, then shift it out of the way of the float if necessary. (This is the behavior of centering a BFC with auto margins.)

@fantasai and I are leaning toward option 1, simply because we already have a way to do option 2 in CSS, and both behaviors are useful in different circumstances. Also, since we're trying to explain the behavior of align using justify-self, the property should be able to duplicate this behavior.

[SelenIT]

Isn't option 1 also what HTML's center element does by default (which appears to be implemented via vendor-prefixed values like -moz-center /-webkit-center for text-align)?

[rachelandrew]

Option 1 seems as if it would be easier to explain / more like existing behaviour. So unless there are strong arguments for 2, I'd prefer 1.

[css-meeting-bot]

The CSS Working Group just discussed Which behavior for block's "justify-self: center"?, and agreed to the following resolutions:

• RESOLVED: Optino #1 from the issue "Reduce the size of the alignment container by the size of the float's margin box, then center the block in the remaining space (this is the behavior of HTML's align attribute)"

The full IRC log of that discussion

<dael> Topic: Which behavior for block's "justify-self: center"?
<dael> Github: https://github.com//issues/1612
<dael> Rossen_: Summery is you have a float and you are positioning a BFC next to it and thisblock has a justify-self: center which means w/o a float it'll b e centered, but since the float is taking space away the justification need to either a) take th float into account or b) don't
<dael> Rossen_: In the case that the bfc has sufficient space to distribute around it the question is which proposal makes more sense? Place the float and then center or center ignoring the float and shift the float if nec.
<dael> Rossen_: As an impl I prefer option 1. I see more people on the issue for option 1. I'd like to hear alternatives or opposing opinions if there are any from the WG.
<dael> [silence]
<dael> Rossen_: If no one has any we can resolve on option #1: the block would be positioned next to the float and centered in that remaining space.
<dael> Rossen_: [Reads] "Reduce the size of the alignment container by the size of the float's margin box, then center the block in the remaining space (this is the behavior of HTML's align attribute)"
<dael> Rossen_: That's the proposal.
<dael> Rossen_: If there are no obj we can resolve.
<fantasai> testcase http://software.hixie.ch/utilities/js/live-dom-viewer/?saved=5281
<dael> Rossen_: fantasai when you discussed with TabAtkins the current proposed is for BFC with fixed width or width which is auto?
<dael> fantasai: Either one. As long as width is smaller than remaining space.
<dael> Rossen_: I was asking b/c if the width is auto and supposed to e xtend out to fill available space css2.1 behavior is already what you desc here.
<dael> Rossen_: The jutification even though there would be centering you wouldn't be able to tell. So I guess this is mostly observable when bfc has fixed size smaller than availablespace and has justification.
<dael> fantasai: Looks like centering with margins for auto has same behavior as centering with center tag.
<dael> Rossen_: For BFC next to floats?
<dael> fantasai: Yeah. Which I wasn't expecting. I was expecting [missed]
<dael> Rossen_: This is the test case you pasted in IRC?
<dael> fantasai: Yeah.
<dael> Rossen_: This is just another confirmation of existing behavior consistant with wha tyou're trying to define.
<dael> Rossen_: I'm going to call for objections on the current proposed behavior. Current proposed is "Reduce the size of the alignment container by the size of the float's margin box, then center the block in the remaining space (this is the behavior of HTML's align attribute)"
<dael> Rossen_: Is there anyone objecting this this?
<dael> RESOLVED: Optino #1 from the issue "Reduce the size of the alignment container by the size of the float's margin box, then center the block in the remaining space (this is the behavior of HTML's align attribute)"

[fantasai]

Testcase: http://software.hixie.ch/utilities/js/live-dom-viewer/?saved=5281