[html5] (no subject)

Ian Hickson ian at hixie.ch
Wed Feb 11 01:37:53 PST 2009

On Tue, 6 Jan 2009, John S. Urban wrote:
> > 
> > Percents aren't allowed currently... what do browsers do with percentage
> > values? Is it useful?
> As most browsers seem to implement them,percent values are useful in 
> that you do not have to redo the coordinates for different sizes of the 
> same image. So if you have a small map for small screens, and a large 
> one for accessibility purposes or for larger screens, the same <MAP> can 
> be used without re-doing the coordinates; whereas pixel values 
> (currently) need redone for each pixmap file.

Fair enough. I've added a comment in the spec suggesting that we might 
want to add this at some future point. I haven't added it yet because 
image maps aren't resized that often as far as I can tell and I'm trying 
to not add new features at this point.

> I find this behavior useful enough to have made a limited-case 
> JavaScript function to supply the desired behavior, which I use in 
> several projects. But this (seemingly simple?) behavior would make a 
> generic, clean and easily understood way to rescale maps to new images 
> sizes.  I meant the example URI to show the usefulness of such a 
> feature; but I might have made the image too simple. The method shown in 
> the example has proven to be very useful with floor plans, maps of 
> geographic locations, ... .

I can imagine it would be quite useful, yes. Have you considered using SVG 
for this kind of thing, by the way?

> PS:  I have been experimenting with replacing the image maps with 
> <CANVAS> elements, but found I had to create my own routines to detect 
> if I was in a polygon or not to do so. SVG supports the features I need 
> to make a scaleable vector-based drawing with clippable regions, but 
> requires external files and so on. Am I correct, or is there a way to 
> use MAP and AREA with a CANVAS ? If there is, that would be another 
> reason to support scaling coordinates; as vector drawings are very well 
> suited to dynamic rescaling (and zooming and clipping, for that matter).

There's no way to use <map> with <canvas> currently. We will be supporting 
<svg> embedded in the same HTML file though.

> PSS: If you make multiple files displaying differently-sized images of 
> the same "picture", and put a single <MAP> in another file, experience 
> shows some browsers seem to have trouble with that. If the URI is 
> anything other than a "#NAME" reference, some browsers fail. This means 
> it is much more work to update an imagemap used in multiple documents.

In HTML5, the usemap="" attribute is no longer a URI at all (just an ID 
ref with a leading "#" for historical reasons).

Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'

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