Allow configuration of borderWidth as object

docs/charts/bar.md

@@ -71,7 +71,8 @@ the color of the bars is generally set this way.
 | [`backgroundColor`](#styling) | [`Color`](../general/colors.md) | Yes | Yes | `'rgba(0, 0, 0, 0.1)'`
 | [`borderColor`](#styling) | [`Color`](../general/colors.md) | Yes | Yes | `'rgba(0, 0, 0, 0.1)'`
 | [`borderSkipped`](#borderskipped) | `string` | Yes | Yes | `'bottom'`
-| [`borderWidth`](#styling) | `number` | Yes | Yes | `0`
+| [`borderWidth`](#borderwidth) | <code>number&#124;object</code> | Yes | Yes | `0`
+| [`borderRadius`](#styling) | `number` | Yes | Yes | `0`
 | [`data`](#data-structure) | `object[]` | - | - | **required**
 | [`hoverBackgroundColor`](#interactions) | [`Color`](../general/colors.md) | - | Yes | `undefined`
 | [`hoverBorderColor`](#interactions) | [`Color`](../general/colors.md) | - | Yes | `undefined`
@@ -97,7 +98,8 @@ The style of each bar can be controlled with the following properties:
 | `backgroundColor` | The bar background color.
 | `borderColor` | The bar border color.
 | [`borderSkipped`](#borderskipped) | The edge to skip when drawing bar.
-| `borderWidth` | The bar border width (in pixels).
+| [`borderWidth`](#borderwidth) | The bar border width (in pixels).
+| `borderRadius` | Rounding corners of outer border edge.
 
 All these values, if `undefined`, fallback to the associated [`elements.rectangle.*`](../configuration/elements.md#rectangle-configuration) options.
 
@@ -107,11 +109,18 @@ This setting is used to avoid drawing the bar stroke at the base of the fill.
 In general, this does not need to be changed except when creating chart types
 that derive from a bar chart.
 
+**Note:** for negative bars in vertical chart, `top` and `bottom` are flipped. Same goes for `left` and `right` in horizontal chart.
+
 Options are:
 * `'bottom'`
 * `'left'`
 * `'top'`
 * `'right'`
+* `false`
+
+#### borderWidth
+
+If this value is a number, it is applied to all sides of the rectangle (left, top, right, bottom), except [`borderSkipped`](#borderskipped). If this value is an object, the `left` property defines the left border width. Similarly the `right`, `top` and `bottom` properties can also be specified. Omitted borders and [`borderSkipped`](#borderskipped) are skipped.
 
 ### Interactions
 

src/controllers/controller.bar.js

@@ -158,6 +158,7 @@ module.exports = DatasetController.extend({
 			borderColor: options.borderColor,
 			borderSkipped: options.borderSkipped,
 			borderWidth: options.borderWidth,
+			borderRadius: options.borderRadius,
 			datasetLabel: dataset.label,
 			label: me.chart.data.labels[index]
 		};
@@ -399,7 +400,8 @@ module.exports = DatasetController.extend({
 			'backgroundColor',
 			'borderColor',
 			'borderSkipped',
-			'borderWidth'
+			'borderWidth',
+			'borderRadius'
 		];
 
 		for (i = 0, ilen = keys.length; i < ilen; ++i) {

src/elements/element.rectangle.js

@@ -2,8 +2,10 @@
 
 var defaults = require('../core/core.defaults');
 var Element = require('../core/core.element');
+var helpers = require('../helpers/index');
 
 var defaultColor = defaults.global.defaultColor;
+var valueOrDefault = helpers.valueOrDefault;
 
 defaults._set('global', {
 	elements: {
@@ -28,22 +30,20 @@ function isVertical(bar) {
  */
 function getBarBounds(bar) {
 	var vm = bar._view;
-	var x1, x2, y1, y2;
+	var x1, x2, y1, y2, half;
 
 	if (isVertical(bar)) {
-		// vertical
-		var halfWidth = vm.width / 2;
-		x1 = vm.x - halfWidth;
-		x2 = vm.x + halfWidth;
+		half = vm.width / 2;
+		x1 = vm.x - half;
+		x2 = vm.x + half;
 		y1 = Math.min(vm.y, vm.base);
 		y2 = Math.max(vm.y, vm.base);
 	} else {
-		// horizontal bar
-		var halfHeight = vm.height / 2;
+		half = vm.height / 2;
 		x1 = Math.min(vm.x, vm.base);
 		x2 = Math.max(vm.x, vm.base);
-		y1 = vm.y - halfHeight;
-		y2 = vm.y + halfHeight;
+		y1 = vm.y - half;
+		y2 = vm.y + half;
 	}
 
 	return {
@@ -54,95 +54,200 @@ function getBarBounds(bar) {
 	};
 }
 
-module.exports = Element.extend({
-	draw: function() {
-		var ctx = this._chart.ctx;
-		var vm = this._view;
-		var left, right, top, bottom, signX, signY, borderSkipped;
-		var borderWidth = vm.borderWidth;
+function parseBorderWidth(value, skipped, maxWidth, maxHeight) {
+	var t, r, b, l;
 
-		if (!vm.horizontal) {
-			// bar
-			left = vm.x - vm.width / 2;
-			right = vm.x + vm.width / 2;
-			top = vm.y;
-			bottom = vm.base;
-			signX = 1;
-			signY = bottom > top ? 1 : -1;
-			borderSkipped = vm.borderSkipped || 'bottom';
-		} else {
-			// horizontal bar
-			left = vm.base;
-			right = vm.x;
-			top = vm.y - vm.height / 2;
-			bottom = vm.y + vm.height / 2;
-			signX = right > left ? 1 : -1;
-			signY = 1;
-			borderSkipped = vm.borderSkipped || 'left';
+	if (helpers.isObject(value)) {
+		t = +value.top || 0;
+		r = +value.right || 0;
+		b = +value.bottom || 0;
+		l = +value.left || 0;
+	} else {
+		t = r = b = l = +value || 0;
+	}
+
+	return {
+		top: Math.min(maxHeight, skipped === 'top' ? 0 : t),
+		right: Math.min(maxWidth, skipped === 'right' ? 0 : r),
+		bottom: Math.min(maxHeight, skipped === 'bottom' ? 0 : b),
+		left: Math.min(maxWidth, skipped === 'left' ? 0 : l)
+	};
+}
+
+function flip(orig, v1, v2) {
+	return orig === v1 ? v2 : orig === v2 ? v1 : orig;
+}
+
+function parseBorderSkipped(bar) {
+	var vm = bar._view;
+	var vertical = isVertical(bar);
+	var borderSkipped = valueOrDefault(vm.borderSkipped, vertical ? 'bottom' : 'left');
+
+	if (vertical && vm.base < vm.y) {
+		borderSkipped = flip(borderSkipped, 'bottom', 'top');
+	}
+	if (!vertical && vm.base > vm.x) {
+		borderSkipped = flip(borderSkipped, 'left', 'right');
+	}
+	return borderSkipped;
+}
+
+// border can be in 1 or 2 sections. build corners for each border in each section
+function buildBorderSections(bounds, inner, border) {
+	var top = 'top';
+	var left = 'left';
+	var right = 'right';
+	var bottom = 'bottom';
+	var borderKeys = [top, right, bottom, left];
+	var corners = [[left, top], [right, top], [right, bottom], [left, bottom]];
+	var sections = [];
+	var current = [];
+	var borderCount = 0;
+	var startIdx = 0;
+	var i, idx, nextIdx, c1, c2;
+
+	// start from a skipped border, so we can close the path
+	for (i = 0; i < 4; ++i) {
+		if (!border[borderKeys[i]]) {
+			startIdx = i;
+			break;
 		}
+	}
 
-		// Canvas doesn't allow us to stroke inside the width so we can
-		// adjust the sizes to fit if we're setting a stroke on the line
-		if (borderWidth) {
-			// borderWidth shold be less than bar width and bar height.
-			var barSize = Math.min(Math.abs(left - right), Math.abs(top - bottom));
-			borderWidth = borderWidth > barSize ? barSize : borderWidth;
-			var halfStroke = borderWidth / 2;
-			// Adjust borderWidth when bar top position is near vm.base(zero).
-			var borderLeft = left + (borderSkipped !== 'left' ? halfStroke * signX : 0);
-			var borderRight = right + (borderSkipped !== 'right' ? -halfStroke * signX : 0);
-			var borderTop = top + (borderSkipped !== 'top' ? halfStroke * signY : 0);
-			var borderBottom = bottom + (borderSkipped !== 'bottom' ? -halfStroke * signY : 0);
-			// not become a vertical line?
-			if (borderLeft !== borderRight) {
-				top = borderTop;
-				bottom = borderBottom;
+	for (i = 0; i < 4; ++i) {
+		idx = (i + startIdx) % 4;
+		if (border[borderKeys[idx]]) {
+			nextIdx = (i + startIdx + 1) % 4;
+			c1 = corners[idx];
+			c2 = corners[nextIdx];
+			// if this is first border, or previous border is skipped, add start corner
+			// previous index is found by adding 3 to keep the index positive in all cases
+			if (i === 0 || !border[borderKeys[(i + startIdx + 3) % 4]]) {
+				if (current.length) {
+					sections.push({count: borderCount, corners: current});
+					current = [];
+					borderCount = 0;
+				}
+				current.push({x1: bounds[c1[0]], y1: bounds[c1[1]], x2: inner[c1[0]], y2: inner[c1[1]]});
 			}
-			// not become a horizontal line?
-			if (borderTop !== borderBottom) {
-				left = borderLeft;
-				right = borderRight;
+			// if this is not last border or next border is skipped, add end corner
+			if (i < 3 || !border[borderKeys[nextIdx]]) {
+				current.push({x1: bounds[c2[0]], y1: bounds[c2[1]], x2: inner[c2[0]], y2: inner[c2[1]]});
 			}
+			borderCount++;
 		}
+	}
+	if (current.length) {
+		sections.push({count: borderCount, corners: current});
+	}
+	return sections;
+}
 
-		ctx.beginPath();
-		ctx.fillStyle = vm.backgroundColor;
-		ctx.strokeStyle = vm.borderColor;
-		ctx.lineWidth = borderWidth;
-
-		// Corner points, from bottom-left to bottom-right clockwise
-		// | 1 2 |
-		// | 0 3 |
-		var corners = [
-			[left, bottom],
-			[left, top],
-			[right, top],
-			[right, bottom]
-		];
-
-		// Find first (starting) corner with fallback to 'bottom'
-		var borders = ['bottom', 'left', 'top', 'right'];
-		var startCorner = borders.indexOf(borderSkipped, 0);
-		if (startCorner === -1) {
-			startCorner = 0;
+function drawBorderSection(ctx, section, borderRadius) {
+	ctx.beginPath();
+
+	var corners = section.corners;
+	var borderCount = section.count;
+	var cornerCount = corners.length;
+	var startCorner = corners[corners.length - 1];
+	var endCorner = corners[0];
+	var ilen = borderCount === 4 ? 5 : borderCount;
+	var i;
+
+	// if all borders are drawn and we have a border radius,
+	// move starting point out ouf the rounded section
+	if (borderRadius && borderCount === 4) {
+		// clone so original corner stays intact
+		endCorner = {x1: endCorner.x1, y1: endCorner.y1, x2: endCorner.x2, y2: endCorner.y2};
+		if (endCorner.x1 === startCorner.x1) {
+			endCorner.x1 += endCorner.x2 > endCorner.x1 ? borderRadius : -borderRadius;
 		}
-
-		function cornerAt(index) {
-			return corners[(startCorner + index) % 4];
+		if (endCorner.y1 === startCorner.y1) {
+			endCorner.y1 += endCorner.y2 > endCorner.y1 ? borderRadius : -borderRadius;
 		}
+	}
+
+	// draw outer edge first
+	ctx.moveTo(endCorner.x1, endCorner.y1);
+	for (i = 0; i < ilen; i++) {
+		startCorner = endCorner;
+		endCorner = corners[(i + 1) % cornerCount];
+		ctx.arcTo(startCorner.x1, startCorner.y1, endCorner.x1, endCorner.y1, borderRadius);
+	}
+
+	// in between edges
+	if (borderCount < 4) {
+		ctx.lineTo(endCorner.x1, endCorner.y1);
+		ctx.lineTo(endCorner.x2, endCorner.y2);
+	} else {
+		// all corners are drawn, close the outer edge
+		startCorner = endCorner;
+		endCorner = corners[0];
+		ctx.closePath();
+		ctx.moveTo(endCorner.x2, endCorner.y2);
+	}
+
+	// draw the inner edge in reverse direction
+	for (; i > 0; --i) {
+		startCorner = endCorner;
+		endCorner = corners[(i - 1) % cornerCount];
+		ctx.arcTo(startCorner.x2, startCorner.y2, endCorner.x2, endCorner.y2, 0);
+	}
+	ctx.lineTo(endCorner.x2, endCorner.y2);
+	ctx.closePath();
+	ctx.fill('evenodd');
+}
 
-		// Draw rectangle from 'startCorner'
-		var corner = cornerAt(0);
-		ctx.moveTo(corner[0], corner[1]);
+module.exports = Element.extend({
+	draw: function() {
+		var me = this;
+		var ctx = me._chart.ctx;
+		var vm = me._view;
+		var borderWidth = vm.borderWidth;
+		var bounds = getBarBounds(me);
+		var left = bounds.left;
+		var top = bounds.top;
+		var right = bounds.right;
+		var bottom = bounds.bottom;
+		var width = right - left;
+		var height = bottom - top;
+		var borderRadius = vm.borderRadius || 0;
+		var inner, i, sections;
 
-		for (var i = 1; i < 4; i++) {
-			corner = cornerAt(i);
-			ctx.lineTo(corner[0], corner[1]);
+		ctx.fillStyle = vm.backgroundColor;
+
+		if (!borderWidth) {
+			ctx.fillRect(left, top, width, height);
+			return;
 		}
 
-		ctx.fill();
-		if (borderWidth) {
-			ctx.stroke();
+		borderWidth = parseBorderWidth(
+			borderWidth,
+			parseBorderSkipped(me),
+			width / 2,
+			height / 2);
+
+		// limit borderRadius to smallest non zero borderWidth
+		borderRadius = Math.min(
+			borderWidth.left || borderRadius,
+			borderWidth.top || borderRadius,
+			borderWidth.right || borderRadius,
+			borderWidth.bottom || borderRadius
+		);
+
+		inner = {
+			left: left + borderWidth.left,
+			top: top + borderWidth.top,
+			right: right - borderWidth.right,
+			bottom: bottom - borderWidth.bottom
+		};
+
+		ctx.fillRect(inner.left, inner.top, inner.right - inner.left, inner.bottom - inner.top);
+
+		ctx.fillStyle = vm.borderColor;
+		sections = buildBorderSections(bounds, inner, borderWidth);
+		for (i = 0; i < sections.length; i++) {
+			drawBorderSection(ctx, sections[i], borderRadius);
 		}
 	},