Bug 15392 - % height inside of auto-height container should result in % computed value but used value is determined as if computed value were 'auto'
% height inside of auto-height container should result in % computed value bu...
Status: NEW
Product: CSS
Classification: Unclassified
Component: CSS Level 2
unspecified
All Windows 3.1
: P2 normal
: ---
Assigned To: Bert Bos
public-css-bugzilla
:
Depends on:
Blocks:
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Reported: 2012-01-02 17:22 UTC by Anton P
Modified: 2013-05-08 18:24 UTC (History)
3 users (show)

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Description Anton P 2012-01-02 17:22:41 UTC
Reported by Peter Moulder, David Baron

10.5 (Content height: the 'height' property) [http://www.w3.org/TR/CSS21/visudet.html#propdef-height] says:

  # Computed value: the percentage or 'auto' (see prose under
  # <percentage>) or the absolute length 

and

  # <percentage>
  #   [...] 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'.

Some implementers want the computed value to remain a percentage and just have the used value be 'auto', since the rule as given constrains implementations to implement the concept of containing block in terms of style data rather than in terms of the rendering tree, which is a significant constraint on implementation modularity.

Conversation begins:
Bug definition:
http://lists.w3.org/Archives/Public/www-style/2011Sep/0008.html
http://lists.w3.org/Archives/Public/www-style/2011Oct/0712.html
Comment 1 Anton P 2012-02-08 09:55:13 UTC
I described the implementor request incorrectly; the used value would not be 'auto' it would be a length.  Hence the request is that % height inside of auto-height container should result in % computed value but used value is determined as if computed value were 'auto'.
Comment 2 fantasai 2013-05-01 21:43:07 UTC
Proposed changes:

  In the computed value line, replace
    # (see prose under <percentage>)
  with
    | (as specified)

  In the <percentage> definition, replace
    | the value computes to 'auto'
  with
    | the used height is calculated as if 'auto' was specified
Comment 3 Gérard Talbot 2013-05-08 18:24:14 UTC
Related tests:

http://test.csswg.org/suites/css2.1/nightly-unstable/html4/height-percentage-002.htm

http://test.csswg.org/suites/css2.1/nightly-unstable/html4/top-115.htm

The text assert of such tests would have to be updated if proposed changes are adopted.