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Archive: 19 February 2009

CSS3 Feedback: Animated Shapes

(This is part of the Feedback on ‘WaSP Community CSS3 Feedback 2008′ series.)

The portion of the feedback devoted to shapes had two overarching themes, as I saw it.  That makes this entry a bit short, but when I tried to combine it with my feedback on “Graphical Effects“, it quickly got too long.  So, a little amuse cerveau, as it were.

Animations, transformations, and so on — the WebKit team have of course been having a field day in this area, and what they’ve done will likely make is way to other browsers.  Or not.  I don’t know.  I’m not entirely thrilled about the effort that’s gone into those properties when there are so many other, more basic things that need love and care, but there’s no denying the essential coolness of slowly rotating an entire page.  Which I totally need to do the next time I give a presentation.

I’m not going to get into the “these things are behavior and therefore JavaScript!” argument.  CSS already does behavior (think :hover) and it’s going to do more over time.  I don’t see how that historical pressure can be resisted for much longer, short of outright refusing to take on any more behaviors and thus making itself a prime candidate for replacement with something else.  We may as well do our best to make sure CSS does good behaviors well, in ways that makes the most sense to the most authors.

So that’s basically my feedback: since we’re going to do it, let’s do it right.  Apple’s made a start, and unless the syntax they’ve defined in their CSS Animations draft is completely unworkable in other browsers for technical reasons, then let’s just roll with it.  And please note I said the syntax, not the overall concept.  (Ditto for their CSS Transforms draft.)

Stuff that isn’t rectangular — including both polygonal element boxes and polygonal floats.  I’ve wanted these for at least a decade, so it’s little surprise that I’m in favor.  Ragged floats were invented as a hack to make the latter happen, of course, and the basic idea’s been improved upon more than once.

The tricky part, of course, is actually defining polygons.  Regular polygons, as in hexagons and octagons and dodecagons, are not terribly difficult; but creating an irregular polygon requires defining a set of point coordinates in relation to some origin and resolving what happens when the lines cross over each other and… well, yeah.

The build-on-what-exists approach would just adopt the syntax HTML area elements use in the coords elements.  There would be two interesting questions there, which are what happens with negative coordinate values, and what happens if you draw a polygon that cuts through some of the element’s content.  For example, you have a div containing an image, and you define the polygon to be smaller (in places) than the image.  Is the browser obligated to prevent content overlap in such cases?  I would tend to say no but I can see arguments for the opposite view, particularly when it comes to floats.

Then there’s the problem that you’d have to define a separate polygon for every element that needed a non-rectangular float, as Bert Bos notes in his thoughts on the topic from a couple of years ago.  His contour idea is certainly interesting, though I’d then start to wonder how you define a contour point on, say, an irregular faded gradient.

Anyway, I thought about adapting clip to the purpose of defining float polygons, but then I remembered the long, tortuous hell that is the history of clip (and offset-clip) and decided that a new property is the way to go.  Clean break, start fresh, et cetera.  I don’t know what it would be called.  content-shape, maybe, to go with element-shape.  Or not.

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