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Re: CSS: %% length unit. Proposal. Some clarifications.

From: David Hyatt <hyatt@apple.com>
Date: Tue, 11 May 2004 15:05:13 -0700
Message-Id: <4739D2EB-A397-11D8-B857-000A958E6110@apple.com>
Cc: www-style@w3.org, "L. David Baron" <dbaron@dbaron.org>
To: Andrew Fedoniouk <news@terrainformatica.com>

The problem I have with your proposal is that you are overloading the 
concept of flexing onto the concept of width.  These are two 
independent concepts.  It should be possible to say that object A has a 
width of 100px but a flex of 5, but that object B has a width of 200px 
and a flex of 1 (or no flex at all, etc.).

If you overload the flexing concept onto width, then you prevent the 
separate specification of width and flex for a single element.

XUL solves this problem by introducing a separate CSS property, 
box-flex, that is implemented by Mozilla and Safari.

Another important flexing concept for UI elements (like scrollbars) is 
levels of flexing.  We call these flex groups in XUL.  Currently only 
Safari implements flex-group support.  The idea is that objects can be 
placed at different flex levels, so that - for example - you might want 
the track of a scrollbar to flex as you shrink the scrollbar, but once 
the track is completely gone, then the up/down buttons on the scrollbar 
could start flexing as you get even smaller.

I think flexing works best when used with a specific new display type 
(a new type of container), so that the rules can be easily specified, 
and you don't have to handle how flexing works in arbitrary line layout 
(which I think would be unnecessarily complicated given the use cases I 
would expect for such a feature) or in the presence of floats.

dave

On May 11, 2004, at 2:57 PM, Andrew Fedoniouk wrote:

>
> For me personally the concept of "auto" is one of the most confusing 
> things
> in CSS:
> Bad dream of implementor: "...'auto' replaced by some suitable value, 
> but
> there are exceptions...".
>
> E.g. why margin-left/right:auto in some cases is exactly 50%% and
> margin-top/bottom:auto is nothing in most(or in all?) cases?
>
> %% is an attempt to formalize this 'auto' concept if you wish.
>
> width:50%  and width:50%%  are basicly the same entities
> but in first place ContainerContentWidth is used as base for computing
> percents and
> in second place it is FreeSpace which is function of 
> ContainerContentWidth.
>
> Andrew Fedoniouk.
> http://terrainformatica.com
>
>
> L. David Baron  wrote:
> "This means that, while it's a value for the 'width' property, it's not
> actually describing the width, but rather a factor to be added to an
> 'auto' width.  That seems confusing, and might lead authors to expect
> that of 'width' in other cases as well (as some buggy browsers already
> do, especially for 'height')"
>
>> first:
>>    compute everything as %% does not exist at all.
>>    apply all paragraph wrapping rules as usual.
>> second:
>>    compute free space for each line box which we've got on first step.
>>    compute all elements which have %% according to free space.
>>    replace elements in line boxes.
>
>
Received on Tuesday, 11 May 2004 18:05:51 GMT

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