chart.js/src/plugins/plugin.title.js

Simple HTML5 charts using the canvas element.

'use strict';

var defaults = require('../core/core.defaults');
var Element = require('../core/core.element');
var helpers = require('../helpers/index');

defaults._set('global', {
	title: {
		display: false,
		fontStyle: 'bold',
		fullWidth: true,
		lineHeight: 1.2,
		padding: 10,
		position: 'top',
		text: '',
		weight: 2000         // by default greater than legend (1000) to be above
	}
});

module.exports = function(Chart) {

	var layout = Chart.layoutService;
	var noop = helpers.noop;

	Chart.Title = Element.extend({
		initialize: function(config) {
			var me = this;
			helpers.extend(me, config);

			// Contains hit boxes for each dataset (in dataset order)
			me.legendHitBoxes = [];
		},

		// These methods are ordered by lifecycle. Utilities then follow.

		beforeUpdate: noop,
		update: function(maxWidth, maxHeight, margins) {
			var me = this;

			// Update Lifecycle - Probably don't want to ever extend or overwrite this function ;)
			me.beforeUpdate();

			// Absorb the master measurements
			me.maxWidth = maxWidth;
			me.maxHeight = maxHeight;
			me.margins = margins;

			// Dimensions
			me.beforeSetDimensions();
			me.setDimensions();
			me.afterSetDimensions();
			// Labels
			me.beforeBuildLabels();
			me.buildLabels();
			me.afterBuildLabels();

			// Fit
			me.beforeFit();
			me.fit();
			me.afterFit();
			//
			me.afterUpdate();

			return me.minSize;

		},
		afterUpdate: noop,

		//

		beforeSetDimensions: noop,
		setDimensions: function() {
			var me = this;
			// Set the unconstrained dimension before label rotation
			if (me.isHorizontal()) {
				// Reset position before calculating rotation
				me.width = me.maxWidth;
				me.left = 0;
				me.right = me.width;
			} else {
				me.height = me.maxHeight;

				// Reset position before calculating rotation
				me.top = 0;
				me.bottom = me.height;
			}

			// Reset padding
			me.paddingLeft = 0;
			me.paddingTop = 0;
			me.paddingRight = 0;
			me.paddingBottom = 0;

			// Reset minSize
			me.minSize = {
				width: 0,
				height: 0
			};
		},
		afterSetDimensions: noop,

		//

		beforeBuildLabels: noop,
		buildLabels: noop,
		afterBuildLabels: noop,

		//

		beforeFit: noop,
		fit: function() {
			var me = this;
			var valueOrDefault = helpers.valueOrDefault;
			var opts = me.options;
			var display = opts.display;
			var fontSize = valueOrDefault(opts.fontSize, defaults.global.defaultFontSize);
			var minSize = me.minSize;
			var lineCount = helpers.isArray(opts.text) ? opts.text.length : 1;
			var lineHeight = helpers.options.toLineHeight(opts.lineHeight, fontSize);
			var textSize = display ? (lineCount * lineHeight) + (opts.padding * 2) : 0;

			if (me.isHorizontal()) {
				minSize.width = me.maxWidth; // fill all the width
				minSize.height = textSize;
			} else {
				minSize.width = textSize;
				minSize.height = me.maxHeight; // fill all the height
			}

			me.width = minSize.width;
			me.height = minSize.height;

		},
		afterFit: noop,

		// Shared Methods
		isHorizontal: function() {
			var pos = this.options.position;
			return pos === 'top' || pos === 'bottom';
		},

		// Actually draw the title block on the canvas
		draw: function() {
			var me = this;
			var ctx = me.ctx;
			var valueOrDefault = helpers.valueOrDefault;
			var opts = me.options;
			var globalDefaults = defaults.global;

			if (opts.display) {
				var fontSize = valueOrDefault(opts.fontSize, globalDefaults.defaultFontSize);
				var fontStyle = valueOrDefault(opts.fontStyle, globalDefaults.defaultFontStyle);
				var fontFamily = valueOrDefault(opts.fontFamily, globalDefaults.defaultFontFamily);
				var titleFont = helpers.fontString(fontSize, fontStyle, fontFamily);
				var lineHeight = helpers.options.toLineHeight(opts.lineHeight, fontSize);
				var offset = lineHeight / 2 + opts.padding;
				var rotation = 0;
				var top = me.top;
				var left = me.left;
				var bottom = me.bottom;
				var right = me.right;
				var maxWidth, titleX, titleY;

				ctx.fillStyle = valueOrDefault(opts.fontColor, globalDefaults.defaultFontColor); // render in correct colour
				ctx.font = titleFont;

				// Horizontal
				if (me.isHorizontal()) {
					titleX = left + ((right - left) / 2); // midpoint of the width
					titleY = top + offset;
					maxWidth = right - left;
				} else {
					titleX = opts.position === 'left' ? left + offset : right - offset;
					titleY = top + ((bottom - top) / 2);
					maxWidth = bottom - top;
					rotation = Math.PI * (opts.position === 'left' ? -0.5 : 0.5);
				}

				ctx.save();
				ctx.translate(titleX, titleY);
				ctx.rotate(rotation);
				ctx.textAlign = 'center';
				ctx.textBaseline = 'middle';

				var text = opts.text;
				if (helpers.isArray(text)) {
					var y = 0;
					for (var i = 0; i < text.length; ++i) {
						ctx.fillText(text[i], 0, y, maxWidth);
						y += lineHeight;
					}
				} else {
					ctx.fillText(text, 0, 0, maxWidth);
				}

				ctx.restore();
			}
		}
	});

	function createNewTitleBlockAndAttach(chart, titleOpts) {
		var title = new Chart.Title({
			ctx: chart.ctx,
			options: titleOpts,
			chart: chart
		});

		layout.configure(chart, title, titleOpts);
		layout.addBox(chart, title);
		chart.titleBlock = title;
	}

	return {
		id: 'title',

		beforeInit: function(chart) {
			var titleOpts = chart.options.title;

			if (titleOpts) {
				createNewTitleBlockAndAttach(chart, titleOpts);
			}
		},

		beforeUpdate: function(chart) {
			var titleOpts = chart.options.title;
			var titleBlock = chart.titleBlock;

			if (titleOpts) {
				helpers.mergeIf(titleOpts, defaults.global.title);

				if (titleBlock) {
					layout.configure(chart, titleBlock, titleOpts);
					titleBlock.options = titleOpts;
				} else {
					createNewTitleBlockAndAttach(chart, titleOpts);
				}
			} else if (titleBlock) {
				Chart.layoutService.removeBox(chart, titleBlock);
				delete chart.titleBlock;
			}
		}
	};
};