Versatile clipping for lines (#6660)

docs/charts/line.md

@@ -51,6 +51,7 @@ The line chart allows a number of properties to be specified for each dataset. T
 | [`borderJoinStyle`](#line-styling) | `string` | Yes | - | `'miter'`
 | [`borderWidth`](#line-styling) | `number` | Yes | - | `3`
 | [`cubicInterpolationMode`](#cubicinterpolationmode) | `string` | Yes | - | `'default'`
+| [`clip`](#line-styling) | <code>number&#124;object</code> | - | - | `borderWidth / 2`
 | [`fill`](#line-styling) | <code>boolean&#124;string</code> | Yes | - | `true`
 | [`hoverBackgroundColor`](#line-styling) | [`Color`](../general/colors.md) | Yes | - | `undefined`
 | [`hoverBorderCapStyle`](#line-styling) | `string` | Yes | - | `undefined`
@@ -117,6 +118,7 @@ The style of the line can be controlled with the following properties:
 | `borderDashOffset` | Offset for line dashes. See [MDN](https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/lineDashOffset).
 | `borderJoinStyle` | Line joint style. See [MDN](https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/lineJoin).
 | `borderWidth` | The line width (in pixels).
+| `clip` | How to clip relative to chartArea. Positive value allows overflow, negative value clips that many pixels inside chartArea. `0` = clip at chartArea. Clipping can also be configured per side: `clip: {left: 5, top: false, right: -2, bottom: 0}`
 | `fill` | How to fill the area under the line. See [area charts](area.md).
 | `lineTension` | Bezier curve tension of the line. Set to 0 to draw straightlines. This option is ignored if monotone cubic interpolation is used.
 | `showLine` | If false, the line is not drawn for this dataset.

src/controllers/controller.line.js

@@ -29,6 +29,51 @@ defaults._set('line', {
 	}
 });
 
+function scaleClip(scale, halfBorderWidth) {
+	var tickOpts = scale && scale.options.ticks || {};
+	var reverse = tickOpts.reverse;
+	var min = tickOpts.min === undefined ? halfBorderWidth : 0;
+	var max = tickOpts.max === undefined ? halfBorderWidth : 0;
+	return {
+		start: reverse ? max : min,
+		end: reverse ? min : max
+	};
+}
+
+function defaultClip(xScale, yScale, borderWidth) {
+	var halfBorderWidth = borderWidth / 2;
+	var x = scaleClip(xScale, halfBorderWidth);
+	var y = scaleClip(yScale, halfBorderWidth);
+
+	return {
+		top: y.end,
+		right: x.end,
+		bottom: y.start,
+		left: x.start
+	};
+}
+
+function toClip(value) {
+	var t, r, b, l;
+
+	if (helpers.isObject(value)) {
+		t = value.top;
+		r = value.right;
+		b = value.bottom;
+		l = value.left;
+	} else {
+		t = r = b = l = value;
+	}
+
+	return {
+		top: t,
+		right: r,
+		bottom: b,
+		left: l
+	};
+}
+
+
 module.exports = DatasetController.extend({
 
 	datasetElementType: elements.Line,
@@ -173,6 +218,7 @@ module.exports = DatasetController.extend({
 		values.spanGaps = valueOrDefault(config.spanGaps, options.spanGaps);
 		values.tension = valueOrDefault(config.lineTension, lineOptions.tension);
 		values.steppedLine = resolve([custom.steppedLine, config.steppedLine, lineOptions.stepped]);
+		values.clip = toClip(valueOrDefault(config.clip, defaultClip(me._xScale, me._yScale, values.borderWidth)));
 
 		return values;
 	},
@@ -275,18 +321,19 @@ module.exports = DatasetController.extend({
 		var meta = me.getMeta();
 		var points = meta.data || [];
 		var area = chart.chartArea;
+		var canvas = chart.canvas;
 		var i = 0;
 		var ilen = points.length;
-		var halfBorderWidth;
+		var clip;
 
 		if (me._showLine) {
-			halfBorderWidth = (meta.dataset._model.borderWidth || 0) / 2;
+			clip = meta.dataset._model.clip;
 
 			helpers.canvas.clipArea(chart.ctx, {
-				left: area.left - halfBorderWidth,
-				right: area.right + halfBorderWidth,
-				top: area.top - halfBorderWidth,
-				bottom: area.bottom + halfBorderWidth
+				left: clip.left === false ? 0 : area.left - clip.left,
+				right: clip.right === false ? canvas.width : area.right + clip.right,
+				top: clip.top === false ? 0 : area.top - clip.top,
+				bottom: clip.bottom === false ? canvas.height : area.bottom + clip.bottom
 			});
 
 			meta.dataset.draw();

test/fixtures/controller.line/clip/default-x-max.json

@@ -0,0 +1,38 @@
+{
+    "config": {
+        "type": "scatter",
+        "data": {
+            "datasets": [{
+                "borderColor": "red",
+                "data": [{"x":-5,"y":5},{"x":-4,"y":6},{"x":-3,"y":7},{"x":-2,"y":6},{"x":-1,"y":5},{"x":0,"y":4},{"x":1,"y":3},{"x":2,"y":2},{"x":3,"y":5},{"x":4,"y":7},{"x":5,"y":9}],
+                "fill": false,
+                "showLine": true,
+                "borderWidth": 20,
+                "pointRadius": 0
+            }]
+        },
+        "options": {
+            "responsive": false,
+            "legend": false,
+            "title": false,
+            "scales": {
+                "xAxes": [{
+                    "ticks": {
+                        "max": 3,
+                        "display": false
+                    }
+                }],
+                "yAxes": [{"ticks": {"display": false}}]
+            },
+            "layout": {
+                "padding": 24
+            }
+        }
+    },
+    "options": {
+        "canvas": {
+            "height": 256,
+            "width": 512
+        }
+    }
+}

test/fixtures/controller.line/clip/default-x-min.json

@@ -0,0 +1,38 @@
+{
+    "config": {
+        "type": "scatter",
+        "data": {
+            "datasets": [{
+                "borderColor": "red",
+                "data": [{"x":-5,"y":5},{"x":-4,"y":6},{"x":-3,"y":7},{"x":-2,"y":6},{"x":-1,"y":5},{"x":0,"y":4},{"x":1,"y":3},{"x":2,"y":2},{"x":3,"y":5},{"x":4,"y":7},{"x":5,"y":9}],
+                "fill": false,
+                "showLine": true,
+                "borderWidth": 20,
+                "pointRadius": 0
+            }]
+        },
+        "options": {
+            "responsive": false,
+            "legend": false,
+            "title": false,
+            "scales": {
+                "xAxes": [{
+                    "ticks": {
+                        "min": -2,
+                        "display": false
+                    }
+                }],
+                "yAxes": [{"ticks": {"display": false}}]
+            },
+            "layout": {
+                "padding": 24
+            }
+        }
+    },
+    "options": {
+        "canvas": {
+            "height": 256,
+            "width": 512
+        }
+    }
+}

test/fixtures/controller.line/clip/default-x.json

@@ -0,0 +1,39 @@
+{
+    "config": {
+        "type": "scatter",
+        "data": {
+            "datasets": [{
+                "borderColor": "red",
+                "data": [{"x":-5,"y":5},{"x":-4,"y":6},{"x":-3,"y":7},{"x":-2,"y":6},{"x":-1,"y":5},{"x":0,"y":4},{"x":1,"y":3},{"x":2,"y":2},{"x":3,"y":5},{"x":4,"y":7},{"x":5,"y":9}],
+                "fill": false,
+                "showLine": true,
+                "borderWidth": 20,
+                "pointRadius": 0
+            }]
+        },
+        "options": {
+            "responsive": false,
+            "legend": false,
+            "title": false,
+            "scales": {
+                "xAxes": [{
+                    "ticks": {
+                        "min": -2,
+                        "max": 3,
+                        "display": false
+                    }
+                }],
+                "yAxes": [{"ticks": {"display": false}}]
+            },
+            "layout": {
+                "padding": 24
+            }
+        }
+    },
+    "options": {
+        "canvas": {
+            "height": 256,
+            "width": 512
+        }
+    }
+}

test/fixtures/controller.line/clip/default-y-max.json

@@ -0,0 +1,38 @@
+{
+    "config": {
+        "type": "scatter",
+        "data": {
+            "datasets": [{
+                "borderColor": "red",
+                "data": [{"x":-5,"y":5},{"x":-4,"y":6},{"x":-3,"y":7},{"x":-2,"y":6},{"x":-1,"y":5},{"x":0,"y":4},{"x":1,"y":3},{"x":2,"y":2},{"x":3,"y":5},{"x":4,"y":7},{"x":5,"y":9}],
+                "fill": false,
+                "showLine": true,
+                "borderWidth": 20,
+                "pointRadius": 0
+            }]
+        },
+        "options": {
+            "responsive": false,
+            "legend": false,
+            "title": false,
+            "scales": {
+                "xAxes": [{"ticks": {"display": false}}],
+                "yAxes": [{
+                    "ticks": {
+                        "max": 6,
+                        "display": false
+                    }
+                }]
+            },
+            "layout": {
+                "padding": 24
+            }
+        }
+    },
+    "options": {
+        "canvas": {
+            "height": 256,
+            "width": 512
+        }
+    }
+}

test/fixtures/controller.line/clip/default-y-min.json

@@ -0,0 +1,38 @@
+{
+    "config": {
+        "type": "scatter",
+        "data": {
+            "datasets": [{
+                "borderColor": "red",
+                "data": [{"x":-5,"y":5},{"x":-4,"y":6},{"x":-3,"y":7},{"x":-2,"y":6},{"x":-1,"y":5},{"x":0,"y":4},{"x":1,"y":3},{"x":2,"y":2},{"x":3,"y":5},{"x":4,"y":7},{"x":5,"y":9}],
+                "fill": false,
+                "showLine": true,
+                "borderWidth": 20,
+                "pointRadius": 0
+            }]
+        },
+        "options": {
+            "responsive": false,
+            "legend": false,
+            "title": false,
+            "scales": {
+                "xAxes": [{"ticks": {"display": false}}],
+                "yAxes": [{
+                    "ticks": {
+                        "min": 2,
+                        "display": false
+                    }
+                }]
+            },
+            "layout": {
+                "padding": 24
+            }
+        }
+    },
+    "options": {
+        "canvas": {
+            "height": 256,
+            "width": 512
+        }
+    }
+}

test/fixtures/controller.line/clip/default-y.json

@@ -0,0 +1,39 @@
+{
+    "config": {
+        "type": "scatter",
+        "data": {
+            "datasets": [{
+                "borderColor": "red",
+                "data": [{"x":-5,"y":5},{"x":-4,"y":6},{"x":-3,"y":7},{"x":-2,"y":6},{"x":-1,"y":5},{"x":0,"y":4},{"x":1,"y":3},{"x":2,"y":2},{"x":3,"y":5},{"x":4,"y":7},{"x":5,"y":9}],
+                "fill": false,
+                "showLine": true,
+                "borderWidth": 20,
+                "pointRadius": 0
+            }]
+        },
+        "options": {
+            "responsive": false,
+            "legend": false,
+            "title": false,
+            "scales": {
+                "xAxes": [{"ticks": {"display": false}}],
+                "yAxes": [{
+                    "ticks": {
+                        "min": 2,
+                        "max": 6,
+                        "display": false
+                    }
+                }]
+            },
+            "layout": {
+                "padding": 24
+            }
+        }
+    },
+    "options": {
+        "canvas": {
+            "height": 256,
+            "width": 512
+        }
+    }
+}