chartjs-plugin-piechart-outlabels/src/helpers.js

Chart.js plugin to display float data labels on pie/doughnut chart outside the border.

'use strict';

import Chart from 'chart.js';

var helpers = Chart.helpers;

export default helpers.merge(helpers, {
	// @todo move this method in Chart.helpers.canvas.toFont (deprecates helpers.fontString)
	// @see https://developer.mozilla.org/en-US/docs/Web/CSS/font
	toFontString: function(font) {
		if (!font || helpers.isNullOrUndef(font.size) || helpers.isNullOrUndef(font.family)) {
			return null;
		}

		return (font.style ? font.style + ' ' : '')
			+ (font.weight ? font.weight + ' ' : '')
			+ font.size + 'px '
			+ font.family;
	},

	// @todo move this in Chart.helpers.canvas.textSize
	// @todo cache calls of measureText if font doesn't change?!
	textSize: function(ctx, lines, font) {
		var items = [].concat(lines);
		var ilen = items.length;
		var prev = ctx.font;
		var width = 0;
		var i;

		ctx.font = font.string;

		for (i = 0; i < ilen; ++i) {
			width = Math.max(ctx.measureText(items[i]).width, width);
		}

		ctx.font = prev;

		return {
			height: ilen * font.lineHeight,
			width: width
		};
	},

	// @todo move this method in Chart.helpers.options.toFont
	parseFont: function(value, height) {
		
		var global = Chart.defaults.global;
		var size = helpers.valueOrDefault(value.size, global.defaultFontSize);

		
		if (value.resizable) {
			size = this.adaptTextSizeToHeight(height, value.minSize, value.maxSize);
		}

		var font = {
			family: helpers.valueOrDefault(value.family, global.defaultFontFamily),
			lineHeight: helpers.options.toLineHeight(value.lineHeight, size),
			size: size,
			style: helpers.valueOrDefault(value.style, global.defaultFontStyle),
			weight: helpers.valueOrDefault(value.weight, null),
			string: ''
		};

		font.string = helpers.toFontString(font);
		return font;
	},

	adaptTextSizeToHeight: function(height, min, max) {
		var size = (height / 100) * 2.5;
		if(min && size < min) {
			return min;
		}
		if(max && size > max) {
			return max;
		}
		return size;
	}
});