larger point/hover radius does not offset tooltip, obscures caret

[jeffzap76]

Using a pointRadius and pointHoverRadius larger than the default results in a tooltip whose caret is buried beneath the point:

I've updated to 2.4.0 in the hopes that some of the recent tooltip-related fixes might have addressed this, but it doesn't appear so.

I reverted to defaults on point and hover radius and border thickness and realized that the caret is actually always somewhat obscured by the point; the tooltip is anchored off the x/y of the true data point and never takes the point size or shape into account, really.

After studying the code, I was able to hack a workaround by overriding the 'average' positioner that is used for determining the tooltip anchor coordinate to include a 'padding' property on its return object that I see would be used to set a local 'caretPadding' property that is already factored into the tooltip position math. I might suggest externalizing this caretPadding concept as it seems like it's very close to the intended spirit of my request, so obviously someone was thinking along these lines. :-)

  var origPositioner = Chart.Tooltip.positioners.average;
  Chart.Tooltip.positioners.average = function(elements, eventPosition) {
    console.log('using override tooltip avg positioner, adding padding');
    var pos = origPositioner(elements, eventPosition);
    pos.padding = 12;
    return pos;
  };

[etimberg]

@jeffzap76 it feels like https://github.com/chartjs/Chart.js/blob/master/src/core/core.tooltip.js#L517 is more of a typo than anything. I don't think any of the positioners were supposed to return padding ... it should come from the options.

[jeffzap76]

I agree - it would seem reasonable for tooltip options to contain that caretPadding property.

[jeffzap76]

Actually my initial report and screenshots are misleading -- I forgot that I was pulling some visual effects off via a plugin with an afterDraw() implementation that was causing the tooltip caret to be drawn over. So that apparent defect is not really a defect.

What remains valid here is to discuss whether caretPadding should be externalized to the options and used to support tooltip positioning offset in case someone doesn't want the caret to point at the dead center of an enlarged data point.