Tooltip improvements

[Fxlr8]

1. I tried to use onMouseMove prop on SparklinesLine component but found it very hard to hit tiny circles that it generates

return (
        <circle
          key={i}
          cx={p.x}
          cy={p.y}
          r={2}
          style={fillStyle}
          onMouseEnter={e => onMouseMove('enter', data[i], p)}
          onClick={e => onMouseMove('click', data[i], p)}
        />
      );

How do you think users should snipe those 2px circles whit a cursor? I think microscopic hardcoded circles are not the best way to trigger tooltip callback, how about rendering transparent rectangles over the chart?

2. The callback function does not return the index of the hovered point, which could be very handy if you want to render a custom tooltip and display more data.

3. There is a bug if you set fill to none in SparklinesLine style the callback function never gets triggered.

I can implement and fix all that stuff if you let me

[SalmaanP]

@Fxlr8 Hey, can you post a snippet of how you used onMouseMove? I'm having trouble understanding how to use it, the docs don't have information for it. Thanks!

[sampathmora]

Hi, can you post snippet for showTooltip ? onMouseMove