[css3-grid-layout] Negative numbers for <grid-line>

Hi everyone,

following last week's minutes [1], negative numbers are allowed for
grid items' grid line. I am supportive of this change (along with
reversing grid-{end|after} to use the start | before edge).

The specification is missing the following clarifications though:

1) Which negative range is allowed for <integer>?

There are several options:
* Match Python which allows negative integers up to -len(array),
something below is in error and resolves to 'auto'. This has the
downside of allowing the auto-placement algorithm to run in some
* Allow arbitrary values, knowing that they would be brought back into
the appropriate range (e.g. using modulo).
* Match what the specification does for numbered named grid line and
clamp the value to - (size of the grid) thus resolving in the first
grid line.

Positively and negatively numbered named grid lines would have to work
the same way, regardless of which option we use.

My preference would be to option 3 as it is arguably the least
surprising from an author's perspective.

2) Interaction with the Automatic Grid Item Placement Algorithm (section 6.3.1)

Currently the specification allows "the position and size of any
explicitly-defined grid items" which would cover negative positions. I
would propose to ignore them for the purpose of sizing the grid based
on what the resolution above.


[1] http://lists.w3.org/Archives/Public/www-style/2013Mar/0355.html

Received on Monday, 25 March 2013 21:16:07 UTC