[cairo] Hit detect surface?

Carl Worth cworth at cworth.org
Wed Mar 1 12:04:42 PST 2006

On Wed, 01 Mar 2006 14:03:43 -0500, wrote:
> Hmm, it's not necessary to do a full tesselation to implement those
> functions -- for fills and strokes with round caps+joins, it's as
> simple as flattening the path and then:

Correct. I was describing the current implementation, and it could
definitely be optimized a bunch. But the point is that there are
bigger savings to be had at a higher-level first.

> However, to be really useful for user interface picking, you'd want
> a tolerance radius, too.  I suppose that could be approximated by
> testing against an appropriately-sized square rather than a point.

In the past, an interface proposed for this was one that returned the
distance from a given point to the nearest point of the stroke or

In fact, a patch to implement that has been sitting in my INBOX since
February of last year (*blush*). I've just committed that now and
pushed it to a new branch of my personal tree. You can fetch that into
an existing tree with:

	git fetch git:///git.cairographics.org/~cworth/cairo distance-to-path

The patch has bit-rotted a little bit, and I might suggest a couple of
API changes in it. I'll commit enough changes to make it compile, then
follow up the list to the original proposal.

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