On Mon, Apr 7, 2014 at 10:36 AM, Daniel Holbert <dholbert@mozilla.com> wrote: > Interesting. > > Here's a perhaps simpler case: suppose a vertical flex container has a > flex item with "height: 10px; flex-basis: 50px", and that flex item has > a child with a percent-valued height. > > Should the percent height resolve against the 10px specified-height, or > against the flex-basis (which we can reliably know ahead of time is what > its used height will end up resolving to)? > > Testcase: http://jsfiddle.net/LcL8U/ > > CSS21 says this about percent height values: > # The percentage is calculated with respect to the > # height of the generated box's containing block. > # If the height of the containing block is not > # specified explicitly (i.e., it depends on content > # height), and this element is not absolutely > # positioned, the value computes to 'auto'." > http://www.w3.org/TR/CSS21/visudet.html#propdef-height > > (We can disregard the second half of this spec text here, since there's > clearly no dependence on content in my or Greg's example, and no browser > seems to be treating the percent height as "auto".) Sigh, bad application of errata strikes again! (We errata'd that to happen at used-value time instead.) > So the question is, what is the "height of the box's containing block". > Blink seems to be saying it's the specified "height" property, while > Gecko/Trident are using the actual box's height (the flex basis). Since > the CSS21 spec text [quoted above] seems to be talking about box height > rather than the "height" property here, I tend to think the > Gecko/Trident behavior is correct. Yes, it's the actual height (the flex basis). I think the spec is clear about this, but I can correct something if it's not. ~TJReceived on Wednesday, 9 April 2014 00:16:56 UTC
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