core.layouts.js

'use strict';

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

function filterByPosition(array, position) {
	return helpers.where(array, function(v) {
		return v.position === position;
	});
}

function sortByWeight(array, reverse) {
	array.forEach(function(v, i) {
		v._tmpIndex_ = i;
		return v;
	});
	array.sort(function(a, b) {
		var v0 = reverse ? b : a;
		var v1 = reverse ? a : b;
		return v0.weight === v1.weight ?
			v0._tmpIndex_ - v1._tmpIndex_ :
			v0.weight - v1.weight;
	});
	array.forEach(function(v) {
		delete v._tmpIndex_;
	});
}

function findMaxPadding(boxes) {
	var top = 0;
	var left = 0;
	var bottom = 0;
	var right = 0;
	helpers.each(boxes, function(box) {
		if (box.getPadding) {
			var boxPadding = box.getPadding();
			top = Math.max(top, boxPadding.top);
			left = Math.max(left, boxPadding.left);
			bottom = Math.max(bottom, boxPadding.bottom);
			right = Math.max(right, boxPadding.right);
		}
	});
	return {
		top: top,
		left: left,
		bottom: bottom,
		right: right
	};
}

function addSizeByPosition(boxes, size) {
	helpers.each(boxes, function(box) {
		size[box.position] += box.isHorizontal() ? box.height : box.width;
	});
}

defaults._set('global', {
	layout: {
		padding: {
			top: 0,
			right: 0,
			bottom: 0,
			left: 0
		}
	}
});

/**
 * @interface ILayoutItem
 * @prop {string} position - The position of the item in the chart layout. Possible values are
 * 'left', 'top', 'right', 'bottom', and 'chartArea'
 * @prop {number} weight - The weight used to sort the item. Higher weights are further away from the chart area
 * @prop {boolean} fullWidth - if true, and the item is horizontal, then push vertical boxes down
 * @prop {function} isHorizontal - returns true if the layout item is horizontal (ie. top or bottom)
 * @prop {function} update - Takes two parameters: width and height. Returns size of item
 * @prop {function} getPadding -  Returns an object with padding on the edges
 * @prop {number} width - Width of item. Must be valid after update()
 * @prop {number} height - Height of item. Must be valid after update()
 * @prop {number} left - Left edge of the item. Set by layout system and cannot be used in update
 * @prop {number} top - Top edge of the item. Set by layout system and cannot be used in update
 * @prop {number} right - Right edge of the item. Set by layout system and cannot be used in update
 * @prop {number} bottom - Bottom edge of the item. Set by layout system and cannot be used in update
 */

// The layout service is very self explanatory.  It's responsible for the layout within a chart.
// Scales, Legends and Plugins all rely on the layout service and can easily register to be placed anywhere they need
// It is this service's responsibility of carrying out that layout.
module.exports = {
	defaults: {},

	/**
	 * Register a box to a chart.
	 * A box is simply a reference to an object that requires layout. eg. Scales, Legend, Title.
	 * @param {Chart} chart - the chart to use
	 * @param {ILayoutItem} item - the item to add to be layed out
	 */
	addBox: function(chart, item) {
		if (!chart.boxes) {
			chart.boxes = [];
		}

		// initialize item with default values
		item.fullWidth = item.fullWidth || false;
		item.position = item.position || 'top';
		item.weight = item.weight || 0;
		item._layers = item._layers || function() {
			return [{
				z: 0,
				draw: function() {
					item.draw.apply(item, arguments);
				}
			}];
		};

		chart.boxes.push(item);
	},

	/**
	 * Remove a layoutItem from a chart
	 * @param {Chart} chart - the chart to remove the box from
	 * @param {ILayoutItem} layoutItem - the item to remove from the layout
	 */
	removeBox: function(chart, layoutItem) {
		var index = chart.boxes ? chart.boxes.indexOf(layoutItem) : -1;
		if (index !== -1) {
			chart.boxes.splice(index, 1);
		}
	},

	/**
	 * Sets (or updates) options on the given `item`.
	 * @param {Chart} chart - the chart in which the item lives (or will be added to)
	 * @param {ILayoutItem} item - the item to configure with the given options
	 * @param {object} options - the new item options.
	 */
	configure: function(chart, item, options) {
		var props = ['fullWidth', 'position', 'weight'];
		var ilen = props.length;
		var i = 0;
		var prop;

		for (; i < ilen; ++i) {
			prop = props[i];
			if (options.hasOwnProperty(prop)) {
				item[prop] = options[prop];
			}
		}
	},

	/**
	 * Fits boxes of the given chart into the given size by having each box measure itself
	 * then running a fitting algorithm
	 * @param {Chart} chart - the chart
	 * @param {number} width - the width to fit into
	 * @param {number} height - the height to fit into
	 */
	update: function(chart, width, height) {
		if (!chart) {
			return;
		}

		var layoutOptions = chart.options.layout || {};
		var padding = helpers.options.toPadding(layoutOptions.padding);
		var leftPadding = padding.left;
		var rightPadding = padding.right;
		var topPadding = padding.top;
		var bottomPadding = padding.bottom;

		var leftBoxes = filterByPosition(chart.boxes, 'left');
		var rightBoxes = filterByPosition(chart.boxes, 'right');
		var topBoxes = filterByPosition(chart.boxes, 'top');
		var bottomBoxes = filterByPosition(chart.boxes, 'bottom');
		var chartAreaBoxes = filterByPosition(chart.boxes, 'chartArea');

		// Sort boxes by weight. A higher weight is further away from the chart area
		sortByWeight(leftBoxes, true);
		sortByWeight(rightBoxes, false);
		sortByWeight(topBoxes, true);
		sortByWeight(bottomBoxes, false);

		var verticalBoxes = leftBoxes.concat(rightBoxes);
		var horizontalBoxes = topBoxes.concat(bottomBoxes);
		var outerBoxes = verticalBoxes.concat(horizontalBoxes);

		// Essentially we now have any number of boxes on each of the 4 sides.
		// Our canvas looks like the following.
		// The areas L1 and L2 are the left axes. R1 is the right axis, T1 is the top axis and
		// B1 is the bottom axis
		// There are also 4 quadrant-like locations (left to right instead of clockwise) reserved for chart overlays
		// These locations are single-box locations only, when trying to register a chartArea location that is already taken,
		// an error will be thrown.
		//
		// |----------------------------------------------------|
		// |                  T1 (Full Width)                   |
		// |----------------------------------------------------|
		// |    |    |                 T2                  |    |
		// |    |----|-------------------------------------|----|
		// |    |    | C1 |                           | C2 |    |
		// |    |    |----|                           |----|    |
		// |    |    |                                     |    |
		// | L1 | L2 |           ChartArea (C0)            | R1 |
		// |    |    |                                     |    |
		// |    |    |----|                           |----|    |
		// |    |    | C3 |                           | C4 |    |
		// |    |----|-------------------------------------|----|
		// |    |    |                 B1                  |    |
		// |----------------------------------------------------|
		// |                  B2 (Full Width)                   |
		// |----------------------------------------------------|
		//
		// What we do to find the best sizing, we do the following
		// 1. Determine the minimum size of the chart area.
		// 2. Split the remaining width equally between each vertical axis
		// 3. Split the remaining height equally between each horizontal axis
		// 4. Give each layout the maximum size it can be. The layout will return it's minimum size
		// 5. Adjust the sizes of each axis based on it's minimum reported size.
		// 6. Refit each axis
		// 7. Position each axis in the final location
		// 8. Tell the chart the final location of the chart area
		// 9. Tell any axes that overlay the chart area the positions of the chart area

		// Step 1
		var chartWidth = width - leftPadding - rightPadding;
		var chartHeight = height - topPadding - bottomPadding;
		var chartAreaWidth = chartWidth / 2; // min 50%

		// Step 2
		var verticalBoxWidth = (width - chartAreaWidth) / verticalBoxes.length;

		// Step 3
		// TODO re-limit horizontal axis height (this limit has affected only padding calculation since PR 1837)
		// var horizontalBoxHeight = (height - chartAreaHeight) / horizontalBoxes.length;

		// Step 4
		var maxChartAreaWidth = chartWidth;
		var maxChartAreaHeight = chartHeight;
		var outerBoxSizes = {top: topPadding, left: leftPadding, bottom: bottomPadding, right: rightPadding};
		var minBoxSizes = [];
		var maxPadding;

		function getMinimumBoxSize(box) {
			var minSize;
			var isHorizontal = box.isHorizontal();

			if (isHorizontal) {
				minSize = box.update(box.fullWidth ? chartWidth : maxChartAreaWidth, chartHeight / 2);
				maxChartAreaHeight -= minSize.height;
			} else {
				minSize = box.update(verticalBoxWidth, maxChartAreaHeight);
				maxChartAreaWidth -= minSize.width;
			}

			minBoxSizes.push({
				horizontal: isHorizontal,
				width: minSize.width,
				box: box,
			});
		}

		helpers.each(outerBoxes, getMinimumBoxSize);

		// If a horizontal box has padding, we move the left boxes over to avoid ugly charts (see issue #2478)
		maxPadding = findMaxPadding(outerBoxes);

		// At this point, maxChartAreaHeight and maxChartAreaWidth are the size the chart area could
		// be if the axes are drawn at their minimum sizes.
		// Steps 5 & 6

		// Function to fit a box
		function fitBox(box) {
			var minBoxSize = helpers.findNextWhere(minBoxSizes, function(minBox) {
				return minBox.box === box;
			});

			if (minBoxSize) {
				if (minBoxSize.horizontal) {
					var scaleMargin = {
						left: Math.max(outerBoxSizes.left, maxPadding.left),
						right: Math.max(outerBoxSizes.right, maxPadding.right),
						top: 0,
						bottom: 0
					};

					// Don't use min size here because of label rotation. When the labels are rotated, their rotation highly depends
					// on the margin. Sometimes they need to increase in size slightly
					box.update(box.fullWidth ? chartWidth : maxChartAreaWidth, chartHeight / 2, scaleMargin);
				} else {
					box.update(minBoxSize.width, maxChartAreaHeight);
				}
			}
		}

		// Update, and calculate the left and right margins for the horizontal boxes
		helpers.each(verticalBoxes, fitBox);
		addSizeByPosition(verticalBoxes, outerBoxSizes);

		// Set the Left and Right margins for the horizontal boxes
		helpers.each(horizontalBoxes, fitBox);
		addSizeByPosition(horizontalBoxes, outerBoxSizes);

		function finalFitVerticalBox(box) {
			var minBoxSize = helpers.findNextWhere(minBoxSizes, function(minSize) {
				return minSize.box === box;
			});

			var scaleMargin = {
				left: 0,
				right: 0,
				top: outerBoxSizes.top,
				bottom: outerBoxSizes.bottom
			};

			if (minBoxSize) {
				box.update(minBoxSize.width, maxChartAreaHeight, scaleMargin);
			}
		}

		// Let the left layout know the final margin
		helpers.each(verticalBoxes, finalFitVerticalBox);

		// Recalculate because the size of each layout might have changed slightly due to the margins (label rotation for instance)
		outerBoxSizes = {top: topPadding, left: leftPadding, bottom: bottomPadding, right: rightPadding};
		addSizeByPosition(outerBoxes, outerBoxSizes);

		// We may be adding some padding to account for rotated x axis labels
		var leftPaddingAddition = Math.max(maxPadding.left - outerBoxSizes.left, 0);
		outerBoxSizes.left += leftPaddingAddition;
		outerBoxSizes.right += Math.max(maxPadding.right - outerBoxSizes.right, 0);

		var topPaddingAddition = Math.max(maxPadding.top - outerBoxSizes.top, 0);
		outerBoxSizes.top += topPaddingAddition;
		outerBoxSizes.bottom += Math.max(maxPadding.bottom - outerBoxSizes.bottom, 0);

		// Figure out if our chart area changed. This would occur if the dataset layout label rotation
		// changed due to the application of the margins in step 6. Since we can only get bigger, this is safe to do
		// without calling `fit` again
		var newMaxChartAreaHeight = height - outerBoxSizes.top - outerBoxSizes.bottom;
		var newMaxChartAreaWidth = width - outerBoxSizes.left - outerBoxSizes.right;

		if (newMaxChartAreaWidth !== maxChartAreaWidth || newMaxChartAreaHeight !== maxChartAreaHeight) {
			helpers.each(verticalBoxes, function(box) {
				box.height = newMaxChartAreaHeight;
			});

			helpers.each(horizontalBoxes, function(box) {
				if (!box.fullWidth) {
					box.width = newMaxChartAreaWidth;
				}
			});

			maxChartAreaHeight = newMaxChartAreaHeight;
			maxChartAreaWidth = newMaxChartAreaWidth;
		}

		// Step 7 - Position the boxes
		var left = leftPadding + leftPaddingAddition;
		var top = topPadding + topPaddingAddition;

		function placeBox(box) {
			if (box.isHorizontal()) {
				box.left = box.fullWidth ? leftPadding : outerBoxSizes.left;
				box.right = box.fullWidth ? width - rightPadding : outerBoxSizes.left + maxChartAreaWidth;
				box.top = top;
				box.bottom = top + box.height;

				// Move to next point
				top = box.bottom;

			} else {

				box.left = left;
				box.right = left + box.width;
				box.top = outerBoxSizes.top;
				box.bottom = outerBoxSizes.top + maxChartAreaHeight;

				// Move to next point
				left = box.right;
			}
		}

		helpers.each(leftBoxes.concat(topBoxes), placeBox);

		// Account for chart width and height
		left += maxChartAreaWidth;
		top += maxChartAreaHeight;

		helpers.each(rightBoxes, placeBox);
		helpers.each(bottomBoxes, placeBox);

		// Step 8
		chart.chartArea = {
			left: outerBoxSizes.left,
			top: outerBoxSizes.top,
			right: outerBoxSizes.left + maxChartAreaWidth,
			bottom: outerBoxSizes.top + maxChartAreaHeight
		};

		// Step 9
		helpers.each(chartAreaBoxes, function(box) {
			box.left = chart.chartArea.left;
			box.top = chart.chartArea.top;
			box.right = chart.chartArea.right;
			box.bottom = chart.chartArea.bottom;

			box.update(maxChartAreaWidth, maxChartAreaHeight);
		});
	}
};