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[css-break][css-backgrounds] Sizing backgrounds across fragments

From: fantasai <fantasai.lists@inkedblade.net>
Date: Thu, 12 Dec 2013 17:00:26 -0800
Message-ID: <52AA5C2A.6080601@inkedblade.net>
To: "www-style@w3.org" <www-style@w3.org>
I just moved the definition of 'box-decoration-break' from CSS3
Backgrounds and Borders to CSS3 Fragmentation. I made a few minor
editorial tweaks and added some more structural markup, but more
importantly, during this move, I noticed a problem with the
definition we have for handling backgrounds across varying-size
fragments:

   # If the box fragments have different widths (heights, if the
   # fragments are joined horizontally), then each piece draws its
   # portion of the background assuming that the whole element has
   # the same width (height) as this piece.
   # This ensures that right-aligned images stay aligned to the
   # right edge, left-aligned images stay aligned to the left edge,
   # and centered images stay centered.

This works fine until you have an image whose height depends on
the box's width. Then the variation in width creates a variation
in vertical progress.

Rossen and I decided to add

   | However, if the used height (width) of an image is derived
   | from the width of the box, then it is calculated using the
   | widest fragment's width and maintained as a fixed size.

This preserves continuity of the background across fragments.

Alternate definitions would use the narrowest fragment or
the first fragment.

Thoughts?

~fantasai
Received on Friday, 13 December 2013 01:00:54 UTC

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