toKey bug about modestmaps-js

[RandomEtc]

Which browser/OS and which version of Modest Maps JS? Can you post a demo somewhere?

Do you have one map on the page, or many?

Does it work if your map is bigger? new mm.Point(256,256) is smaller than I've tested, perhaps that's the issue?

[olehz]

I tested Modest Maps JS v0.13.4 and v0.13.3

Windows/Browsers: Mozilla, Chrome, Opera.
And Safari from IPhone.

Example: http://nadoloni.com/mm.html

I think, that "toKey" return not unique values

[RandomEtc]

Ah, oh dear. You're right:

new com.modestmaps.Coordinate(5605, 9261, 14).toKey()
1680518083
new com.modestmaps.Coordinate(5606, 9262, 14).toKey()
1680518083

I guess that hashing function isn't the right thing for Modest Maps. A short term solution is just to concatenate the row/col/zoom as a String. I liked the hashing because it was quite a bit faster than string manipulation in some browsers, but obviously correctness is more important than raw speed.

Try adding the following before instantiating your map, to override the default behavior until we can add a patch:

com.modestmaps.Coordinate.prototype.toKey = function () {
    return this.container().toString();
}

A better one might be involve bitwise hashing based on the known distributions of zoom, row and colum, e.g. this.zoom << 24 + this.column << 12 + this.row but I'm not going to bet on it without more testing since I got it wrong with the current function :)

[RandomEtc]

Thanks again for reporting this bug! I just committed a very simple fix: 1b3a646