scale.linear.js

'use strict';

var helpers = require('../helpers/index');
var LinearScaleBase = require('./scale.linearbase');
var Ticks = require('../core/core.ticks');

var defaultConfig = {
	position: 'left',
	ticks: {
		callback: Ticks.formatters.linear
	}
};

var DEFAULT_MIN = 0;
var DEFAULT_MAX = 1;

function getMatchingVisibleMetas(scale) {
	var isHorizontal = scale.isHorizontal();

	return scale.chart._getSortedVisibleDatasetMetas()
		.filter(function(meta) {
			return isHorizontal ? meta.xAxisID === scale.id : meta.yAxisID === scale.id;
		});
}

function getOrCreateStack(stacks, stacked, meta) {
	var key = [
		meta.type,
		// we have a separate stack for stack=undefined datasets when the opts.stacked is undefined
		stacked === undefined && meta.stack === undefined ? meta.index : '',
		meta.stack
	].join('.');

	if (stacks[key] === undefined) {
		stacks[key] = {
			pos: [],
			neg: []
		};
	}

	return stacks[key];
}

function isInvalidOrHidden(value, meta, i) {
	return isNaN(value.min) || isNaN(value.max) || meta.data[i].hidden;
}

function initStackIndex(pos, neg, i) {
	pos[i] = pos[i] || 0;
	neg[i] = neg[i] || 0;
}

function isNegative(value) {
	return value.min < 0 || value.max < 0;
}

function stackData(scale, stacks, meta, data) {
	var opts = scale.options;
	var stacked = opts.stacked;
	var stack = getOrCreateStack(stacks, stacked, meta);
	var pos = stack.pos;
	var neg = stack.neg;
	var ilen = data.length;
	var i, value;

	for (i = 0; i < ilen; ++i) {
		initStackIndex(pos, neg, i);

		value = scale._parseValue(data[i]);
		if (isInvalidOrHidden(value, meta, i)) {
			continue;
		}

		if (opts.relativePoints) {
			pos[i] = 100;
		} else if (isNegative(value)) {
			neg[i] += value.min;
		} else {
			pos[i] += value.max;
		}
	}
}

function updateMinMax(scale, meta, data) {
	var ilen = data.length;
	var i, value;

	for (i = 0; i < ilen; ++i) {
		value = scale._parseValue(data[i]);
		if (isInvalidOrHidden(value, meta, i)) {
			continue;
		}

		scale.min = Math.min(scale.min, value.min);
		scale.max = Math.max(scale.max, value.max);
	}
}

module.exports = LinearScaleBase.extend({
	determineDataLimits: function() {
		var me = this;
		var opts = me.options;
		var chart = me.chart;
		var datasets = chart.data.datasets;
		var metasets = getMatchingVisibleMetas(me);
		var hasStacks = opts.stacked;
		var stacks = {};
		var ilen = metasets.length;
		var i, meta, data, values;

		me.min = Number.POSITIVE_INFINITY;
		me.max = Number.NEGATIVE_INFINITY;

		if (hasStacks === undefined) {
			for (i = 0; !hasStacks && i < ilen; ++i) {
				meta = metasets[i];
				hasStacks = meta.stack !== undefined;
			}
		}

		for (i = 0; i < ilen; ++i) {
			meta = metasets[i];
			data = datasets[meta.index].data;
			if (hasStacks) {
				stackData(me, stacks, meta, data);
			} else {
				updateMinMax(me, meta, data);
			}
		}

		helpers.each(stacks, function(stackValues) {
			values = stackValues.pos.concat(stackValues.neg);
			me.min = Math.min(me.min, helpers.min(values));
			me.max = Math.max(me.max, helpers.max(values));
		});

		me.min = helpers.isFinite(me.min) && !isNaN(me.min) ? me.min : DEFAULT_MIN;
		me.max = helpers.isFinite(me.max) && !isNaN(me.max) ? me.max : DEFAULT_MAX;

		// Common base implementation to handle ticks.min, ticks.max, ticks.beginAtZero
		me.handleTickRangeOptions();
	},

	// Returns the maximum number of ticks based on the scale dimension
	_computeTickLimit: function() {
		var me = this;
		var tickFont;

		if (me.isHorizontal()) {
			return Math.ceil(me.width / 40);
		}
		tickFont = helpers.options._parseFont(me.options.ticks);
		return Math.ceil(me.height / tickFont.lineHeight);
	},

	// Called after the ticks are built. We need
	handleDirectionalChanges: function() {
		if (!this.isHorizontal()) {
			// We are in a vertical orientation. The top value is the highest. So reverse the array
			this.ticks.reverse();
		}
	},

	getLabelForIndex: function(index, datasetIndex) {
		return this._getScaleLabel(this.chart.data.datasets[datasetIndex].data[index]);
	},

	// Utils
	getPixelForValue: function(value) {
		// This must be called after fit has been run so that
		// this.left, this.top, this.right, and this.bottom have been defined
		var me = this;
		var start = me.start;

		var rightValue = +me.getRightValue(value);
		var pixel;
		var range = me.end - start;

		if (me.isHorizontal()) {
			pixel = me.left + (me.width / range * (rightValue - start));
		} else {
			pixel = me.bottom - (me.height / range * (rightValue - start));
		}
		return pixel;
	},

	getValueForPixel: function(pixel) {
		var me = this;
		var isHorizontal = me.isHorizontal();
		var innerDimension = isHorizontal ? me.width : me.height;
		var offset = (isHorizontal ? pixel - me.left : me.bottom - pixel) / innerDimension;
		return me.start + ((me.end - me.start) * offset);
	},

	getPixelForTick: function(index) {
		var ticks = this.ticksAsNumbers;
		if (index < 0 || index > ticks.length - 1) {
			return null;
		}
		return this.getPixelForValue(ticks[index]);
	}
});

// INTERNAL: static default options, registered in src/index.js
module.exports._defaults = defaultConfig;