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Re: [css-break][css-masking][css-shapes] fragmentation

From: Dirk Schulze <dschulze@adobe.com>
Date: Tue, 14 Jan 2014 09:26:46 +0000
To: fantasai <fantasai.lists@inkedblade.net>
CC: www-style list <www-style@w3.org>, Alan Stearns <stearns@adobe.com>
Message-ID: <A7647DB3-6EEB-4AB5-A066-77B6E4AD14E1@adobe.com>

On Jan 13, 2014, at 11:32 PM, fantasai <fantasai.lists@inkedblade.net> wrote:

> On 01/10/2014 12:52 PM, Dirk Schulze wrote:
>> 
>> * The first article views breaks on equally sized fragment containers.
>> (The first consideration there seems to be what CSS Fragmentations intended.)
>> * The second article views breaks on differently sized fragment containers.
>> This is probably the interesting part which is not covered by CSS Fragmentation.
> 
> Fragmentation extensively covers breaking into variable-sized
> fragmentainers:
>  http://dev.w3.org/csswg/css-break/#varying-size-boxes
>  http://dev.w3.org/csswg/css-break/#joining-boxes
> 
> What aspect of variable-size fragmentation is not covered?

I think it is not complete.

List item 2 in your list says that layout is performed per fragment. Each fragment starts from the break point of the previous one. But size and position is *recalculated* to the current fragment. (Note that the first list item seem to imply that intrinsic sizing depends on the layout of the first fragment container while the second list item clearly says otherwise.)

Lets go on with the second list item:
* Imagine an element is split into two fragment containers with auto height and a width of 100px for the first container and a width of 200px for the second container. It just happens that (based on the content) the first fragment will have a height of 50px, the second of 100px.

Container 1
+----+
|    |
|    |

Container 2
|        |
|        |
|        |
|        |
+--------+

(| and - represent 25px)

* You have a radial gradient or a clipping circle with a radius of 50px positioned 50px,50px from the top left of the content box.

You will see the upper half of the gradient/clipping circle on the first fragment.

Since the first sentence in list item says that you continue after the break as you stopped before the break, the second part of the gradient/circle starts at the top of the second fragment container.

But the sentence in list item 2 continues: “recalculating sizes and positions using its own size”. This implies that the position of top left of the content box is recalculated based on the metrics of the second box. Suddenly the position shifts closer to the break and you will see more than half of the gradient in the second fragmentation container. I do not believe that this is the expected behavior of web authors.

This is what I tried to explain in the third consideration of [1].

Greetings,
Dirk

[1] http://blogs.adobe.com/webplatform/2014/01/10/fragmentation-of-masked-and-clipped-content-part-2/

> 
> ~fantasai
Received on Tuesday, 14 January 2014 09:27:17 UTC

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