Share min sample size with all bars on same scale (#7897)

Share min sample size with all bars on same scale

src/controllers/controller.bar.js

@@ -1,24 +1,43 @@
 import DatasetController from '../core/core.datasetController';
-import {clipArea, unclipArea} from '../helpers/helpers.canvas';
-import {isArray, isNullOrUndef, valueOrDefault, resolveObjectKey} from '../helpers/helpers.core';
-import {_limitValue, sign} from '../helpers/helpers.math';
+import {
+	clipArea, unclipArea, _arrayUnique, isArray, isNullOrUndef,
+	valueOrDefault, resolveObjectKey, _limitValue, sign
+} from '../helpers';
+
+function getAllScaleValues(scale) {
+	if (!scale._cache.$bar) {
+		const metas = scale.getMatchingVisibleMetas('bar');
+		let values = [];
+
+		for (let i = 0, ilen = metas.length; i < ilen; i++) {
+			values = values.concat(metas[i].controller.getAllParsedValues(scale));
+		}
+		scale._cache.$bar = _arrayUnique(values.sort((a, b) => a - b));
+	}
+	return scale._cache.$bar;
+}
 
 /**
  * Computes the "optimal" sample size to maintain bars equally sized while preventing overlap.
  * @private
  */
-function computeMinSampleSize(scale, pixels) {
+function computeMinSampleSize(scale) {
+	const values = getAllScaleValues(scale);
 	let min = scale._length;
-	let prev, curr, i, ilen;
+	let i, ilen, curr, prev;
+	const updateMinAndPrev = () => {
+		min = Math.min(min, i && Math.abs(curr - prev) || min);
+		prev = curr;
+	};
 
-	for (i = 1, ilen = pixels.length; i < ilen; ++i) {
-		min = Math.min(min, Math.abs(pixels[i] - pixels[i - 1]));
+	for (i = 0, ilen = values.length; i < ilen; ++i) {
+		curr = scale.getPixelForValue(values[i]);
+		updateMinAndPrev();
 	}
 
 	for (i = 0, ilen = scale.ticks.length; i < ilen; ++i) {
 		curr = scale.getPixelForTick(i);
-		min = i > 0 ? Math.min(min, Math.abs(curr - prev)) : min;
-		prev = curr;
+		updateMinAndPrev();
 	}
 
 	return min;
@@ -365,7 +384,7 @@ export default class BarController extends DatasetController {
 		// only if the barThickness option is defined
 		// Since a scriptable option may return null or undefined that
 		// means the option would have to be of type number
-		const min = computeMinSampleSize(iScale, pixels);
+		const min = computeMinSampleSize(iScale);
 
 		return {
 			min,

src/core/core.scale.js

@@ -344,6 +344,7 @@ export default class Scale extends Element {
 		this._userMin = undefined;
 		this._ticksLength = 0;
 		this._borderValue = 0;
+		this._cache = {};
 	}
 
 	/**
@@ -418,7 +419,9 @@ export default class Scale extends Element {
 		return {min, max};
 	}
 
-	invalidateCaches() {}
+	invalidateCaches() {
+		this._cache = {};
+	}
 
 	/**
 	 * Get the padding needed for the scale

test/fixtures/controller.bar/bar-thickness-min-interval-multi.json

@@ -0,0 +1,44 @@
+{
+    "config": {
+        "type": "bar",
+        "data": {
+            "datasets": [{
+                "backgroundColor": "#FF6384",
+                "barPercentage": 1,
+                "categoryPercentage": 1,
+                "data": [{"x": "2001", "y": 1}, {"x": "2099", "y": 5}]
+            }, {
+                "backgroundColor": "#8463FF",
+                "barPercentage": 1,
+                "categoryPercentage": 1,
+                "data": [{"x": "2019", "y": 2}, {"x": "2020", "y": 3}]
+            }]
+        },
+        "options": {
+            "responsive": false,
+            "legend": false,
+            "title": false,
+            "scales": {
+                "x": {
+                    "type": "time",
+                    "display": false,
+                    "min": "2000",
+                    "max": "2100",
+                    "time": {
+                        "parser": "YYYY"
+                    }
+                },
+                "y": {
+                    "display": false,
+                    "beginAtZero": true
+                }
+            }
+        }
+    },
+    "options": {
+        "canvas": {
+            "height": 256,
+            "width": 512
+        }
+    }
+}