RE: [css3-background] background-size and zero length

Elaborating...

I see 3 different renderings in 3 different browsers, so I’d like to make sure I understand it correctly.

From: Brian Manthos
Sent: Tuesday, May 11, 2010 8:58 AM
To: 'Brad Kemper'
Cc: www-style@w3.org
Subject: RE: [css3-background] background-size and zero length

Where is the rounding rule for the zero case defined?

I see it defined for the non-zero case, as you observed as well.

Is the zero case rounding rule left as UA-defined?


I’m not clear on how to follow this rule without an equation or having it specified in prose:
If ‘background-repeat<http://dev.w3.org/csswg/css3-background/#background-repeat>’ is ‘round’ for one (or both) dimensions, there is a second step. The UA must scale the image in that dimension (or both dimensions) so that it fits a whole number of times in the background positioning area.


Thanks,
-Brian

From: Brad Kemper [mailto:brad.kemper@gmail.com]
Sent: Tuesday, May 11, 2010 8:39 AM
To: Brian Manthos
Cc: www-style@w3.org
Subject: Re: [css3-background] background-size and zero length


On May 11, 2010, at 7:04 AM, Brian Manthos wrote:

Typo.  Mea culpa.

The style rule should have been...

div
{
        background: url(http://www.microsoft.com/favicon.ico) 5px 5px;
        background-size: 0px 20px;
        background-repeat:round;
        width:12px;
        height:17px;
}

-Brian

[...]
How many images should be rendered and at what size?

An infinite number, with zero width for each tile. Rounding does not change that, because the "If X ≠ 0 is the width of the image after step one" part is not fulfilled.

A tile with no width or no height cannot be drawn, so you shouldn't try.

That's how I understand it, anyway.