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) {
			helpers.extend(this, config);
			this.options = helpers.configMerge(Chart.defaults.global.title, config.options);

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

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

		beforeUpdate: noop,
		update: function(maxWidth, maxHeight, margins) {

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

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

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

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

			return this.minSize;

		},
		afterUpdate: noop,

		//

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

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

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

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

		//

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

		//

		beforeFit: noop,
		fit: function() {

			var ctx = this.ctx,
				valueOrDefault = helpers.getValueOrDefault,
				opts = this.options,
				globalDefaults = Chart.defaults.global,
				display = opts.display,
				fontSize = valueOrDefault(opts.fontSize, globalDefaults.defaultFontSize),
				minSize = this.minSize;

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

			this.width = minSize.width;
			this.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 ctx = this.ctx,
				valueOrDefault = helpers.getValueOrDefault,
				opts = this.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;

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

				// Horizontal
				if (this.isHorizontal()) {
					titleX = this.left + ((this.right - this.left) / 2); // midpoint of the width
					titleY = this.top + ((this.bottom - this.top) / 2); // midpoint of the height
				} else {
					titleX = opts.position === 'left' ? this.left + (fontSize / 2) : this.right - (fontSize / 2);
					titleY = this.top + ((this.bottom - this.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();
			}
		}
	});
};