Re: [css-device-adapt] Zero sized viewport lengths and zoom values

I support these changes.

Kenneth


On Thu, May 2, 2013 at 1:43 PM, Rune Lillesveen <rune@opera.com> wrote:

> Hi.
>
> There are two related issues about zero widths/heights in @viewport
> reported by me[1] and Simon Pieters[2].
>
> I'd like to resolve these issues by allowing zero lengths for
> <viewport-length>s, both for descriptor values and resolved/used values.
>
> Rationale:
>
> 1. It's already possible to get zero-length widths and heights for
> viewports established by iframes.
>
> 2. Range checking[3] for calc() requires a closed interval value range.
> The current range is open.
>
> Realizing that even initial viewports can have 0 lengths for width and
> height (in particular through iframes), means the spec should say something
> about potential division-by-zero in the constraining procedure.
>
> Also, for the sake of range checking of calc(), I'd like to change to
> allow 0 values for the various *zoom descriptor values. In practice, a UA
> will have a lower limit on the used value for zoom, so I don't think this
> change will mean anything in practice.
>
>
> Proposed changes:
>
> 1. Change all requirements for lengths in descriptors from "positive" to
> "non-negative".
>
> 2. Change all requirements for zoom factors in descriptors from "positive"
> to "non-negative".
>
> To avoid division-by-zero problems in the constraining procedure:
>
> 3. Change:
>
>   "7. If width is ‘auto’, set width = height * (initial-width /
> initial-height)"
>
>   to:
>
>   "7. If width is ‘auto’, set width = height * (initial-width /
> initial-height), or width = initial-width if initial-height is 0."
>
>   and change:
>
>   "8. If height is ‘auto’, set height = width * (initial-height /
> initial-width)"
>
>   to:
>
>   "8. If height is ‘auto’, set height = width * (initial-height /
> initial-width), or height = initial-height if initial-width is 0."
>
>
> Issue [2] is about my test-suite checking for non-zero used values of
> viewport lengths. That can be resolved by me changing the test-suite.
>
>
> [1] https://www.w3.org/Bugs/**Public/show_bug.cgi?id=21782<https://www.w3.org/Bugs/Public/show_bug.cgi?id=21782>
> [2] https://www.w3.org/Bugs/**Public/show_bug.cgi?id=20289<https://www.w3.org/Bugs/Public/show_bug.cgi?id=20289>
> [3] http://dev.w3.org/csswg/css-**values/#calc-range<http://dev.w3.org/csswg/css-values/#calc-range>
>
> --
> Rune Lillesveen
>
>


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