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Re: [css-grid] Content-size tracks and orthogonal flows

From: Javier Fernandez <jfernandez@igalia.com>
Date: Fri, 18 Dec 2015 18:55:26 +0100
To: www-style list <www-style@w3.org>, fantasai <fantasai.lists@inkedblade.net>, "Tab Atkins Jr." <jackalmage@gmail.com>
Message-ID: <5674488E.7010103@igalia.com>

Using this old thread to add some additional doubts that came out while
implementing orthogonal flows support for Grid Layout.

On 12/19/2014 09:38 PM, fantasai wrote:
> On 02/10/2014 01:47 PM, Simon Sapin wrote:
>> However, this only works if the grid item and grid container have
>> "parallel" writing modes. (Ie. both vertical or both
>> horizontal.) What happens if a grid item is an "orthogonal flow"? (As
>> defined in css-writing-modes.)
>>> If the minimum content size of any Grid item has changed based on
>>> available height for the Grid item as computed in step 2, adjust the
>>> min content size of the Grid item and restart the Grid track Sizing
>>> algorithm (once only).

Assuming a grid item establishing an orthogonal flow, with both
width and height as 'auto', I'd like to clarify if the following assumptions
are correct and compliant with the current Grid Layout spec.

1- Column track's size is based on item's logical height for orthogonal

The track sizing algorithm defined in the spec states that we must start
computing the column track's width. In the case of an item with an
flow, this operation would imply using its logical height. This may be
kind of
obvious but I'd prefer someone confirming this is a valid assumption because
the rest of my arguments are based on it.

2- We may have to estimate row track's size in order to determine item's
logical height.

So, since we might not know yet the item's logical height (width could be
auto and it would depend on the row track breadth, which we haven't
computed yet), we can estimate it, as the spec indicates:

  "If calculating the layout of a grid item in this step depends on the
available space in the block axis, assume the available space that it
would have if any row with a definite max track sizing function had that
size and all other rows were infinite."

Based on the assumed row track's breadth, we can determine grid
item's logical height and set the column track's breadth accordingly.

3- Row track's size is based on item's (min/max) preferred width for
orthogonal flows.

Next step in the track sizing algorithm is to determine row track's breadth,
which would depend on the item's width. We are assuming that in case of
orthogonal flows, row track's size doesn't depend on column track's size,
but just on its content (like it happens when computing column track's size
based on parallel items).

For content-sized column tracks and items with parallel flow we are using
minPreferredWidth and maxPreferredWidth for min-content and max-content
track's sizes respectively. These values are then used as track's baseSize
and growthLimit, respectively, during the track sizing algorithm.

In order to compute row track's min-content and max-content sizes, based
on orthogonal grid items, we are using also those minPreferredWidth and
maxPreferredWidth values. Is this assumption compliant with the specs ?

I think that's all, for now.
Thanks for your feedback.

Received on Friday, 18 December 2015 17:56:03 UTC

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