[cairo] Path length

[Behdad Esfahbod]

On 15-03-24 01:45 PM, Bryce Harrington wrote:
> On Tue, Mar 24, 2015 at 05:09:50PM +0000, Stuart Axon wrote:
>> Is the best way to get the length of a cairo path to call cairo_copy_path_flat and sum the lengths of the LINE_TOs contained inside ?

That's what I've personally done in the past.  However:

>> I've been looking at arc lengths and it seems it can get complex,

There are very decent and simple approximations that I think are good enough
for most purposes.  Read here for example:

  http://pomax.github.io/bezierinfo/#arclength

Would be interesting to measure or calculate the error of that approximation
for small values of n.


>> any chance of cairo providing cairo_path_length in future, or should I be looking at something like 2geom for this sort of thing ?
>>  S++
> 
> I haven't seen anyone making plans to implement that, so 2geom might be
> your best choice right now.  That said, I imagine patches to add that to
> cairo would be entertained if the use case for it is strong enough.

Would be nice, but we'd need a nice API for it too.

> Bryce
>