[OpenLayers-Dev] VML rendering in IE is slow with big geometries. Proposed Fix.

Erik Uzureau erik.uzureau at metacarta.com
Tue Oct 16 23:57:15 EDT 2007

On 10/16/07, Christopher Schmidt <crschmidt at metacarta.com> wrote:
> On Wed, Oct 17, 2007 at 11:58:17AM +1000, Roald de Wit wrote:
> > The same slowdown most probably applies to the other drawing methods in
> > this class.
> >
> > My question is: what would be the best way to tackle this?
> Interesting. I'd always followed the type of behavior you're suggsting
> in Python, but had never known it was needed in JS. (It's always bugged
> me that we just shoved strings together in Javascript, but it seemed
> like everyone did it, so I didn't question.)
> The typical way I do this in Python is to just do the equivilant of:
> var stringList = [];
> for (var i = 0; i < 10000; i++) { stringList.push('foo'); }
> var string = stringList.join("");
> I think we can even skip the .join("") and use .toString() in JS, but I
> have no idea how portable that is, and it feels slightly hacky.
> So, I don't see any need for a stringBuffer object, since it would just
> be an array (with 'push' replaced with 'append').
> With these performance numbers in hand, I think that migrating any
> significant use of string concatanation -- which I think only includes
> the renderers, and maybe things like getParameterString -- to be array
> based makes sense, and I'm in support of that path. It probably makes
> sense to write at least basic tests for the renderer functionality
> before proceeding with this, to ensure that it doesn't break with the
> new code in any way that we can be aware of ahead of time.

Wow. Cool trick. Can't see where else in the OL code it would make
much of a difference other than:

-GeoRSS parseData() -- 197
- BaseTypes String camelize -- 87

how many times is getParameterString() called?


> Regards,
> --
> Christopher Schmidt
> MetaCarta
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