Introduce the 'minBarLength' bar option (chartjs#5741)

Author: adube

docs/charts/bar.md

@@ -97,6 +97,7 @@ The bar chart defines the following configuration options. These options are mer
 | `categoryPercentage` | `Number` | `0.8` | Percent (0-1) of the available width each category should be within the sample width. [more...](#barpercentage-vs-categorypercentage)
 | `barThickness` | `Number/String` | | Manually set width of each bar in pixels. If set to `'flex'`, it computes "optimal" sample widths that globally arrange bars side by side. If not set (default), bars are equally sized based on the smallest interval. [more...](#barthickness)
 | `maxBarThickness` | `Number` | | Set this to ensure that bars are not sized thicker than this.
+| `minBarLength` | `Number` | | Set this to ensure that bars have a minimum length in pixels.
 | `gridLines.offsetGridLines` | `Boolean` | `true` | If true, the bars for a particular data point fall between the grid lines. The grid line will move to the left by one half of the tick interval. If false, the grid line will go right down the middle of the bars. [more...](#offsetgridlines)
 
 ### barThickness

src/controllers/controller.bar.js

@@ -382,8 +382,10 @@ module.exports = function(Chart) {
 			var chart = me.chart;
 			var meta = me.getMeta();
 			var scale = me.getValueScale();
+			var isHorizontal = scale.isHorizontal();
 			var datasets = chart.data.datasets;
 			var value = scale.getRightValue(datasets[datasetIndex].data[index]);
+			var minBarLength = scale.options.minBarLength;
 			var stacked = scale.options.stacked;
 			var stack = meta.stack;
 			var start = 0;
@@ -410,6 +412,15 @@ module.exports = function(Chart) {
 			head = scale.getPixelForValue(start + value);
 			size = (head - base) / 2;
 
+			if (minBarLength !== undefined && Math.abs(size) < minBarLength) {
+				size = minBarLength;
+				if (value >= 0 && !isHorizontal || value < 0 && isHorizontal) {
+					head = base - minBarLength;
+				} else {
+					head = base + minBarLength;
+				}
+			}
+
 			return {
 				size: size,
 				base: base,

test/specs/scale.linear.tests.js

@@ -1046,4 +1046,52 @@ describe('Linear Scale', function() {
 
 		expect(chart.scales['x-axis-0'].max).toEqual(0);
 	});
+
+	it('minBarLength settings should be used on Y axis on bar chart', function() {
+		var minBarLength = 4;
+		var chart = window.acquireChart({
+			type: 'bar',
+			data: {
+				datasets: [{
+					data: [0.05, -0.05, 10, 15, 20, 25, 30, 35]
+				}]
+			},
+			options: {
+				scales: {
+					yAxes: [{
+						minBarLength: minBarLength
+					}]
+				}
+			}
+		});
+
+		var data = chart.getDatasetMeta(0).data;
+
+		expect(data[0]._model.base - minBarLength).toEqual(data[0]._model.y);
+		expect(data[1]._model.base + minBarLength).toEqual(data[1]._model.y);
+	});
+
+	it('minBarLength settings should be used on X axis on horizontalBar chart', function() {
+		var minBarLength = 4;
+		var chart = window.acquireChart({
+			type: 'horizontalBar',
+			data: {
+				datasets: [{
+					data: [0.05, -0.05, 10, 15, 20, 25, 30, 35]
+				}]
+			},
+			options: {
+				scales: {
+					xAxes: [{
+						minBarLength: minBarLength
+					}]
+				}
+			}
+		});
+
+		var data = chart.getDatasetMeta(0).data;
+
+		expect(data[0]._model.base + minBarLength).toEqual(data[0]._model.x);
+		expect(data[1]._model.base - minBarLength).toEqual(data[1]._model.x);
+	});
 });