Rewrite filler (#6795)

Filler plugin is rewritten and test coverage increased

Author: kurkle

docs/general/performance.md

@@ -89,7 +89,7 @@ new Chart(ctx, {
 
 ### Automatic data decimation during draw
 
-Line element will automatically decimate data, when the following conditions are met: `tension` is `0`, `steppedLine` is `false` (default), `fill` is `false` and `borderDash` is `[]` (default).`
+Line element will automatically decimate data, when the following conditions are met: `tension` is `0`, `steppedLine` is `false` (default) and `borderDash` is `[]` (default).`
 This improves rendering speed by skipping drawing of invisible line segments.
 
 ```javascript
@@ -109,6 +109,26 @@ new Chart(ctx, {
 });
 ```
 
+### Enable spanGaps
+
+If you have a lot of data points, it can be more performant to enable `spanGaps`. This disables segmentation of the line, which can be an unneeded step.
+
+To enable `spanGaps`:
+
+```javascript
+new Chart(ctx, {
+    type: 'line',
+    data: {
+        datasets: [{
+            spanGaps: true // enable for a single dataset
+        }]
+    },
+    options: {
+        spanGaps: true // enable for all datasets
+    }
+});
+```
+
 ### Disable Line Drawing
 
 If you have a lot of data points, it can be more performant to disable rendering of the line for a dataset and only draw points. Doing this means that there is less to draw on the canvas which will improve render performance.

src/controllers/controller.line.js

@@ -77,9 +77,8 @@ module.exports = DatasetController.extend({
 
 		// Update Line
 		if (showLine && mode !== 'resize') {
-
 			const properties = {
-				_children: points,
+				points,
 				options: me._resolveDatasetElementOptions()
 			};
 

src/controllers/controller.radar.js

@@ -90,10 +90,11 @@ module.exports = DatasetController.extend({
 		const meta = me._cachedMeta;
 		const line = meta.dataset;
 		const points = meta.data || [];
-
+		const labels = meta.iScale._getLabels();
 		const properties = {
-			_children: points,
+			points,
 			_loop: true,
+			_fullLoop: labels.length === points.length,
 			options: me._resolveDatasetElementOptions()
 		};
 
@@ -122,10 +123,11 @@ module.exports = DatasetController.extend({
 			const y = reset ? scale.yCenter : pointPosition.y;
 
 			const properties = {
-				x: x,
-				y: y,
+				x,
+				y,
+				angle: pointPosition.angle,
 				skip: isNaN(x) || isNaN(y),
-				options,
+				options
 			};
 
 			me._updateElement(point, index, properties, mode);

src/core/core.scale.js

@@ -876,12 +876,9 @@ class Scale extends Element {
 	}
 
 	getBaseValue() {
-		var me = this;
-		var min = me.min;
-		var max = me.max;
+		const {min, max} = this;
 
-		return me.beginAtZero ? 0 :
-			min < 0 && max < 0 ? max :
+		return min < 0 && max < 0 ? max :
 			min > 0 && max > 0 ? min :
 			0;
 	}