[css-break] Breaking inside an inline-block element?

Hi,

Can I please ask a clarification on the CSS Fragmentation spec?

The "unforced break points" section states that Class 2 breakpoints are available "Between line boxes inside a block container box". My first question is: is an inline-block element a "block container box" or not?



My second qusestion is: 

Provided you've a set of inline-block elements to be displayed in a multi-column layout, so that the inline-block elements have so tall lines they don't fit in any of the columns vertically, but are so few wide that multiple ones can find horizontally in one line if needed {see attached test case}...

[ xxx yyy zzz |             ]
[ xxx yyy zzz |             ]
[ xxx yyy zzz |             ]
[ xxx yyy zzz |             ]
[ xxx yyy zzz |             ]
[ xxx yyy zzz |             ]
[ xxx yyy zzz |             ]
  xxx yyy zzz               
  xxx yyy zzz               
  xxx yyy zzz               
  xxx yyy zzz               

... if a browser choose to use a break point between the lines of one of the inline-block element, does that break point inside the inline-block element force all the other inline-block elements to be moved to the next column too (so that you can only see one inline-block element per column)...

[ xxx         |     yyy     ] ...
[ xxx         |     yyy     ] ...
[ xxx         |     yyy     ] ...
[ xxx         | xxx yyy     ] ...
[ xxx         | xxx yyy     ] ...
[ xxx         | xxx yyy     ] ...
[ xxx         | xxx yyy     ] ...
 

... or can the browser make the assumption that the break point inside the inline-block is only valid for that particular inline-box and therefore display the sibling inline-box elements.

[ xxx yyy zzz | xxx yyy zzz ]
[ xxx yyy zzz | xxx yyy zzz ]
[ xxx yyy zzz | xxx yyy zzz ]
[ xxx yyy zzz | xxx yyy zzz ]
[ xxx yyy zzz |             ]
[ xxx yyy zzz |             ]
[ xxx yyy zzz |             ]



(hints: do not look at what webkit does to give me an answer, webkit do not introduce any break point and uses the replaced element image-slicing-based fragmentation algorithm to render; gecko also consider the line of inline-boxes like a replaced element but choose not to fragment which is valid according to the current spec [1]; IE is the only browser that actually fragment on an exact line but I don't know if that's following any valid standards algorithm or not).



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[1] http://lists.w3.org/Archives/Public/www-style/2013Apr/0654.html