Chart.js/src/core/core.title.js

"use strict";

module.exports = function(Chart) {

	var helpers = Chart.helpers;

	Chart.defaults.global.title = {
		display: false,
		position: 'top',
		fullWidth: true, // marks that this box should take the full width of the canvas (pushing down other boxes)

		fontStyle: 'bold',
		padding: 10,

		// actual title
		text: ''
	};

	var noop = helpers.noop;
	Chart.Title = Chart.Element.extend({

		initialize: function(config) {
			var me = this;
			helpers.extend(me, config);
			me.options = helpers.configMerge(Chart.defaults.global.title, config.options);

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

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

		beforeUpdate: function () {
			var chartOpts = this.chart.options;
			if (chartOpts && chartOpts.title) {
				this.options = helpers.configMerge(Chart.defaults.global.title, chartOpts.title);
			}
		},
		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,
				ctx = me.ctx,
				valueOrDefault = helpers.getValueOrDefault,
				opts = me.options,
				globalDefaults = Chart.defaults.global,
				display = opts.display,
				fontSize = valueOrDefault(opts.fontSize, globalDefaults.defaultFontSize),
				minSize = me.minSize;

			if (me.isHorizontal()) {
				minSize.width = me.maxWidth; // fill all the width
				minSize.height = display ? fontSize + (opts.padding * 2) : 0;
			} else {
				minSize.width = display ? fontSize + (opts.padding * 2) : 0;
				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";
		},

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

			if (opts.display) {
				var fontSize = valueOrDefault(opts.fontSize, globalDefaults.defaultFontSize),
					fontStyle = valueOrDefault(opts.fontStyle, globalDefaults.defaultFontStyle),
					fontFamily = valueOrDefault(opts.fontFamily, globalDefaults.defaultFontFamily),
					titleFont = helpers.fontString(fontSize, fontStyle, fontFamily),
					rotation = 0,
					titleX, 
					titleY,
					top = me.top,
					left = me.left,
					bottom = me.bottom,
					right = me.right;

				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 + ((bottom - top) / 2); // midpoint of the height
				} else {
					titleX = opts.position === 'left' ? left + (fontSize / 2) : right - (fontSize / 2);
					titleY = top + ((bottom - top) / 2);
					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';
				ctx.fillText(opts.text, 0, 0);
				ctx.restore();
			}
		}
	});

	// Register the title plugin
	Chart.pluginService.register({
		beforeInit: function(chartInstance) {
			var opts = chartInstance.options;
			var titleOpts = opts.title;

			if (titleOpts) {
				chartInstance.titleBlock = new Chart.Title({
					ctx: chartInstance.chart.ctx,
					options: titleOpts,
					chart: chartInstance
				});

				Chart.layoutService.addBox(chartInstance, chartInstance.titleBlock);
			}
		}
	});
};