Legend bound creation does not consider observed values

[jameshadfield]

The creation of legend bounds for continuous scales uses hardcoded minimum (0) and maximum (10,000):

auspice/src/util/colorScale.js

Lines 394 to 404 in 57c27b3

	function createLegendBounds(legendValues) {
	const valBetween = (x0, x1) => x0 + 0.5*(x1-x0);
	const len = legendValues.length;
	const legendBounds = {};
	legendBounds[legendValues[0]] = [0, valBetween(legendValues[0], legendValues[1])];
	for (let i = 1; i < len - 1; i++) {
	legendBounds[legendValues[i]] = [valBetween(legendValues[i-1], legendValues[i]), valBetween(legendValues[i], legendValues[i+1])];
	}
	legendBounds[legendValues[len-1]] = [valBetween(legendValues[len-2], legendValues[len-1]), 10000];
	return legendBounds;
	}

This is problematic for continuous scales which exceed this range. Using this example, the lowest legend value of -4.51 has legend bounds of [0, -3.97]. This results in problems similar to those fixed in #1643.

A better solution would be to consider all observed values in the tree to create these bounds, especially as we already collect them during continuous scale creation.

The function linked above is used in two other places (ordinal scales which are all integers, fall-through grey-colorscale), and their usage should also be re-evaluated.

[corneliusroemer]

Is this related to #1626 #1653 ?