- From: Dirk Schulze <dschulze@adobe.com>
- Date: Mon, 26 May 2014 07:58:34 +0000
- To: Tab Atkins Jr. <jackalmage@gmail.com>
- CC: FX <public-fx@w3.org>, www-style <www-style@w3.org>
On May 26, 2014, at 2:05 AM, Tab Atkins Jr. <jackalmage@gmail.com> wrote: > On Sun, May 25, 2014 at 12:10 AM, Dirk Schulze <dschulze@adobe.com> wrote: >> On May 23, 2014, at 11:32 PM, Tab Atkins Jr. <jackalmage@gmail.com> wrote: >>>> 2) If no Element was passed, what is the fallback for relative of percentage values? >>> >>> Generally speaking, these types of things are resolved against a 0 >>> length. I suppose that em/rem/etc should be resolved against the UA >>> default font and font-size. >> >> I checked MSCSSMatrix and WebKitCSSMatrix. Both have a method called setMatrixValue which takes a DOMString as argument. This DOMString takes a <transform-list> in the CSS Transforms notation. Percentage length values and relative length values throw a SyntaxError exception for both engines. It is at least another possibility. I am not sure if UAs can access font data without a document even though it should be possible. > > Yeah, only accepting absolute values is definitely a possibility. > There are potentially some relative lengths that might work - if > there's a reasonable way to associate the call with some default > viewport, it's possible that the viewport-relative units would work, > for example. However, that probably wouldn't work in a Worker, for > instance. > > Thinking about it, it seems likely that any relative units that could > be resolved to an absolute length without at least a document for > context are probably actually just absolute lengths, and we'd refer to > them as such. So, it's probably fine to declare that only absolute > lengths are allowed in the string arguments. I changed the spec to the described behavior of MSCSSMatrix and WebKitCSSMatrix. (Both seem to have the constructor taking a DOMString as well with the same behavior as setMatrixValue.) I close the issue for now. Anyone can feel free to raise it again and we can explore the Element argument further. Greetings, Dirk > > ~TJ
Received on Monday, 26 May 2014 07:59:28 UTC