Re: [css-writing-modes][svg] SVG and writing-mode


> On May 7, 2015, at 6:22 AM, Koji Ishii <kojiishi@gmail.com> wrote:
> 
> Not sure where to post cross-WG thing, IIUC cross-posting is not
> recommended, so let me start here.

The mailing list to address both, SVG and CSS members would be public-fx@w3.org. The joint task force of both WGs.

Greetings,
Dirk

> 
> An issue was brought up asking whether SVG viewBox is logical or
> physical when containing HTML has writing-mode: vertical-*. I think
> this is easy -- physical -- and should be confirmed at www-svg if
> needed.
> 
> But then checking CSS Writing Modes brought up a couple of CSS questions.
> 
> 1. Is SVG "images" or "content involving text"?
> 
> CSS Writing Modes defines[1]:
> 
> * The content of replaced elements do not rotate due to the writing
> mode: images, for example, remain upright.
> 
> but then defines:
> 
> * However replaced content involving text (such as MathML content or
> form elements) should match the replaced element’s writing mode and
> line orientation
> 
> I suppose SVG belongs to images rather than "involving text" here even
> if SVG contains text.
> 
> 2. Does writing-mode: vertical-rl in HTML inherits to SVG?
> 
> The other one is how CSS writing-mode applies to text in SVG; i.e., if
> there were <text> in SVG, and the containing HTML is vertical-rl,
> should the <text> be vertical or not?
> 
> Current implementation is a bit complicated. WebKit/Blink applies
> -webkit-writing-mode to HTML, and writing-mode to SVG, so if author
> specifies -webkit-writing-mode: vertical-rl, it does not affect SVG.
> But this behavior may change when unprefixed, depends on how we
> unprefix.
> 
> Trident supports writing-mode in 2003 CR syntax for HTML, which is the
> same as the current SVG syntax. Applying writing-mode: tb applies both
> to HTML and SVG text.
> 
> I couldn't test Gecko; when I applied vertical-rl to <body> and put
> SVG in it, it does not render as of today's nightly.
> 
> # Proposal
> 
> While SVG might need some clarification in their spec if needed, I
> think part of the problem come from the CSS definition where it
> renders SVG upright (assuming my understanding above is correct) but
> still writing-mode value is vertical and is inherited into SVG.
> 
> My proposal hence is CSS defines:
> 1. Clarify SVG should render upright
> 2. Upright-rendered replaced elements have default writing-mode to horizontal-tb
> 
> Stopping writing-mode inheritance at SVG boundary not only prevents
> issues today, but also future issues when SVG changes its syntax, and
> helps authors to not to surprise by all text in SVG images being
> vertical when document's writing-mode was changed.
> 
> Thoughts?
> 
> [1] http://dev.w3.org/csswg/css-writing-modes-3/#block-flow

> [2] http://dev.w3.org/csswg/css-writing-modes-3/#svg-writing-mode

> 
> /koji
>

Received on Saturday, 13 June 2015 06:40:10 UTC