From 5a24bfa500a35000de8eddce2ebdcb4efd6c1d41 Mon Sep 17 00:00:00 2001
From: SAiTO TOSHiKi <saito@koyo-se.net>
Date: Sun, 4 Dec 2016 05:09:45 +0800
Subject: [PATCH] Implement clipping (#3658)

Implements clipping of items outside the chart area. Resolves #3506 #3491 #2873
---
 src/controllers/controller.bar.js  |  2 ++
 src/controllers/controller.line.js |  4 +++-
 src/core/core.canvasHelpers.js     | 12 ++++++++++++
 src/elements/element.point.js      | 24 +++++++++++++++++++++++-
 4 files changed, 40 insertions(+), 2 deletions(-)

diff --git a/src/controllers/controller.bar.js b/src/controllers/controller.bar.js
index e5070542e88..bf1fb693793 100644
--- a/src/controllers/controller.bar.js
+++ b/src/controllers/controller.bar.js
@@ -229,12 +229,14 @@ module.exports = function(Chart) {
 			var dataset = me.getDataset();
 			var i, len;
 
+			Chart.canvasHelpers.clipArea(me.chart.chart.ctx, me.chart.chartArea);
 			for (i = 0, len = metaData.length; i < len; ++i) {
 				var d = dataset.data[i];
 				if (d !== null && d !== undefined && !isNaN(d)) {
 					metaData[i].transition(easingDecimal).draw();
 				}
 			}
+			Chart.canvasHelpers.unclipArea(me.chart.chart.ctx);
 		},
 
 		setHoverStyle: function(rectangle) {
diff --git a/src/controllers/controller.line.js b/src/controllers/controller.line.js
index 23d4eedc402..806ab4f3f58 100644
--- a/src/controllers/controller.line.js
+++ b/src/controllers/controller.line.js
@@ -292,14 +292,16 @@ module.exports = function(Chart) {
 				points[i].transition(easingDecimal);
 			}
 
+			Chart.canvasHelpers.clipArea(me.chart.chart.ctx, me.chart.chartArea);
 			// Transition and Draw the line
 			if (lineEnabled(me.getDataset(), me.chart.options)) {
 				meta.dataset.transition(easingDecimal).draw();
 			}
+			Chart.canvasHelpers.unclipArea(me.chart.chart.ctx);
 
 			// Draw the points
 			for (i=0, ilen=points.length; i<ilen; ++i) {
-				points[i].draw();
+				points[i].draw(me.chart.chartArea);
 			}
 		},
 
diff --git a/src/core/core.canvasHelpers.js b/src/core/core.canvasHelpers.js
index 42fac5c00b5..553730c7373 100644
--- a/src/core/core.canvasHelpers.js
+++ b/src/core/core.canvasHelpers.js
@@ -109,4 +109,16 @@ module.exports = function(Chart) {
 
 		ctx.stroke();
 	};
+
+	helpers.clipArea = function(ctx, clipArea) {
+		ctx.save();
+		ctx.beginPath();
+		ctx.rect(clipArea.left, clipArea.top, clipArea.right - clipArea.left, clipArea.bottom - clipArea.top);
+		ctx.clip();
+	};
+
+	helpers.unclipArea = function(ctx) {
+		ctx.restore();
+	};
+
 };
diff --git a/src/elements/element.point.js b/src/elements/element.point.js
index fe3a6696bd1..c68edc7861b 100644
--- a/src/elements/element.point.js
+++ b/src/elements/element.point.js
@@ -56,13 +56,17 @@ module.exports = function(Chart) {
 				padding: vm.radius + vm.borderWidth
 			};
 		},
-		draw: function() {
+		draw: function(chartArea) {
 			var vm = this._view;
+			var model = this._model;
 			var ctx = this._chart.ctx;
 			var pointStyle = vm.pointStyle;
 			var radius = vm.radius;
 			var x = vm.x;
 			var y = vm.y;
+			var color = Chart.helpers.color;
+			var errMargin = 1.01; // 1.01 is margin for Accumulated error. (Especially Edge, IE.)
+			var ratio = 0;
 
 			if (vm.skip) {
 				return;
@@ -72,6 +76,24 @@ module.exports = function(Chart) {
 			ctx.lineWidth = helpers.getValueOrDefault(vm.borderWidth, globalOpts.elements.point.borderWidth);
 			ctx.fillStyle = vm.backgroundColor || defaultColor;
 
+			// Cliping for Points.
+			// going out from inner charArea?
+			if ((chartArea !== undefined) && ((model.x < chartArea.left) || (chartArea.right*errMargin < model.x) || (model.y < chartArea.top) || (chartArea.bottom*errMargin < model.y))) {
+				// Point fade out
+				if (model.x < chartArea.left) {
+					ratio = (x - model.x) / (chartArea.left - model.x);
+				} else if (chartArea.right*errMargin < model.x) {
+					ratio = (model.x - x) / (model.x - chartArea.right);
+				} else if (model.y < chartArea.top) {
+					ratio = (y - model.y) / (chartArea.top - model.y);
+				} else if (chartArea.bottom*errMargin < model.y) {
+					ratio = (model.y - y) / (model.y - chartArea.bottom);
+				}
+				ratio = Math.round(ratio*100) / 100;
+				ctx.strokeStyle = color(ctx.strokeStyle).alpha(ratio).rgbString();
+				ctx.fillStyle = color(ctx.fillStyle).alpha(ratio).rgbString();
+			}
+
 			Chart.canvasHelpers.drawPoint(ctx, pointStyle, radius, x, y);
 		}
 	});