Adds different point styles

[mathiask88]

@etimberg I added some point styles like in Excel:

I know tests are failing, but I wanted to know what do you think of this, before changing the tests.

[etimberg]

@mathiask88 I like the idea! Would make a great addition to v2.

[mathiask88]

Added tests and rebased.

[etimberg]

Looks good. Thanks @mathiask88

[mathiask88]

Cool, for the sake of completeness here an example of how it's looking:

Do you know why the last triangle looks different? :S

[etimberg]

Looks like it might not stroke properly.

[Raf2k]

Hi.

How I can add my own point styles?

[mathiask88]

@Raf2k Just look at the changes made in element.point.js

@etimberg Looks like the colors get mixed up somewhere. It's always a color of another dataset and if there is only one dataset everything looks good.

[etimberg]

@mathiask88 I didn't notice any colour issues. Do you have a jsfiddle?

[Raf2k]

@mathiask88 I see that I should replace method draw to add my own point styles. (I don't want to hack original lib) Is this what you mean? Maybe something like this:

Chart.elements.Point.styles.myOwnStyleName = function() {...}

will be better? And draw function will handle this styles?

[mathiask88]

@Raf2k Something like this? https://github.com/mathiask88/Chart.js/commit/8636ae2fc888ef0f5e8cc500595d5af680b8b6ed
With that fix you can assign a custom HTMLCanvasElement or HTMLImageElement to the pointStyle option that is drawn instead of the built in styles. (Not tested)

Edit: updated link

[mathiask88]

@etimberg What do you think of the mentioned addition? Something the majority would appreciate?

[etimberg]

@mathiask88 I think it would make a good addition :)

[mathiask88]

#2031