A 0px legend border becomes .5px instead

[Pikamander2]

If you try to set the legend's border to 0px, it becomes .5px instead. This causes a faint border to appear around the legend's color, which is undesirable.

Making the label's color value fully transparent ("rgba(0,0,0,0)") fixes this in Chrome, but not Firefox.

Here's an example: http://codepen.io/anon/pen/GjRKLX

Here's that example, scaled 3x to make it more obvious: http://codepen.io/anon/pen/yaLBky

The reason why this occurs is because, when setting canvas's lineWidth property, "zero, negative, Infinity and NaN values are ignored" and instead replaced with a value of 0.5.

To avoid this problem, Chart.js shouldn't draw the border if the borderWidth is set to 0.

[Pikamander2]

The issue can be fixed by checking the desired width:

var isLineWidthZero = (itemOrDefault(legendItem.lineWidth, lineDefault.borderWidth) === 0);

and then using that to decide whether a stroke should be drawn:

if (!isLineWidthZero)
{
    ctx.strokeRect(x, y, boxWidth, fontSize);
}

[etimberg]

Fixed in #3242