Cartesian scale tick backdrop (#8931)

docs/axes/_common_ticks.md

@@ -4,12 +4,15 @@ Namespace: `options.scales[scaleId].ticks`
 
 | Name | Type | Scriptable | Default | Description
 | ---- | ---- | :-------------------------------: | ------- | -----------
+| `backdropColor` | [`Color`](../../general/colors.md) | Yes | `'rgba(255, 255, 255, 0.75)'` | Color of label backdrops.
+| `backdropPadding` | [`Padding`](../../general/padding.md) | Yes | `2` | Padding of label backdrop.
 | `callback` | `function` | | | Returns the string representation of the tick value as it should be displayed on the chart. See [callback](/axes/labelling.md#creating-custom-tick-formats).
 | `display` | `boolean` | | `true` | If true, show tick labels.
 | `color` | [`Color`](/general/colors.md) | Yes | `Chart.defaults.color` | Color of ticks.
 | `font` | `Font` | Yes | `Chart.defaults.font` | See [Fonts](/general/fonts.md)
 | `major` | `object` | | `{}` | [Major ticks configuration](/axes/styling.md#major-tick-configuration).
 | `padding` | `number` | | `3` | Sets the offset of the tick labels from the axis
+| `showLabelBackdrop` | `boolean` | Yes | `true` for radial scale, `false` otherwise | If true, draw a background behind the tick labels.
 | `textStrokeColor` | [`Color`](/general/colors.md) | Yes | `` | The color of the stroke around the text.
 | `textStrokeWidth` | `number` | Yes | `0` | Stroke width around the text.
 | `z` | `number` | | `0` | z-index of tick layer. Useful when ticks are drawn on chart area. Values <= 0 are drawn under datasets, > 0 on top.

docs/axes/radial/linear.md

@@ -28,14 +28,11 @@ Namespace: `options.scales[scaleId].ticks`
 
 | Name | Type | Scriptable | Default | Description
 | ---- | ---- | ------- | ------- | -----------
-| `backdropColor` | [`Color`](../../general/colors.md) | Yes | `'rgba(255, 255, 255, 0.75)'` | Color of label backdrops.
-| `backdropPadding` | [`Padding`](../../general/padding.md) | Yes | `2` | Padding of label backdrop.
 | `count` | `number` | Yes | `undefined` | The number of ticks to generate. If specified, this overrides the automatic generation.
 | `format` | `object` | Yes | | The [`Intl.NumberFormat`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/NumberFormat) options used by the default label formatter
 | `maxTicksLimit` | `number` | Yes | `11` | Maximum number of ticks and gridlines to show.
 | `precision` | `number` | Yes | | if defined and `stepSize` is not specified, the step size will be rounded to this many decimal places.
 | `stepSize` | `number` | Yes | | User defined fixed step size for the scale. [more...](#step-size)
-| `showLabelBackdrop` | `boolean` | Yes | `true` | If true, draw a background behind the tick labels.
 
 !!!include(axes/_common_ticks.md)!!!
 

src/core/core.scale.defaults.js

@@ -71,6 +71,10 @@ defaults.set('scale', {
     major: {},
     align: 'center',
     crossAlign: 'near',
+
+    showLabelBackdrop: false,
+    backdropColor: 'rgba(255, 255, 255, 0.75)',
+    backdropPadding: 2,
   }
 });
 

src/core/core.scale.js

@@ -773,7 +773,7 @@ export default class Scale extends Element {
   }
 
   /**
-	 * @return {{ first: object, last: object, widest: object, highest: object }}
+	 * @return {{ first: object, last: object, widest: object, highest: object, widths: Array, heights: array }}
 	 * @private
 	 */
   _getLabelSizes() {
@@ -796,7 +796,7 @@ export default class Scale extends Element {
   /**
 	 * Returns {width, height, offset} objects for the first, last, widest, highest tick
 	 * labels where offset indicates the anchor point offset from the top in pixels.
-	 * @return {{ first: object, last: object, widest: object, highest: object }}
+	 * @return {{ first: object, last: object, widest: object, highest: object, widths: Array, heights: array }}
 	 * @private
 	 */
   _computeLabelSizes(ticks, length) {
@@ -845,7 +845,9 @@ export default class Scale extends Element {
       first: valueAt(0),
       last: valueAt(length - 1),
       widest: valueAt(widest),
-      highest: valueAt(highest)
+      highest: valueAt(highest),
+      widths,
+      heights,
     };
   }
 
@@ -1226,6 +1228,48 @@ export default class Scale extends Element {
         textOffset = (1 - lineCount) * lineHeight / 2;
       }
 
+      let backdrop;
+
+      if (optsAtIndex.showLabelBackdrop) {
+        const labelPadding = toPadding(optsAtIndex.backdropPadding);
+        const height = labelSizes.heights[i];
+        const width = labelSizes.widths[i];
+
+        let top = y + textOffset - labelPadding.top;
+        let left = x - labelPadding.left;
+
+        switch (textBaseline) {
+        case 'middle':
+          top -= height / 2;
+          break;
+        case 'bottom':
+          top -= height;
+          break;
+        default:
+          break;
+        }
+
+        switch (textAlign) {
+        case 'center':
+          left -= width / 2;
+          break;
+        case 'right':
+          left -= width;
+          break;
+        default:
+          break;
+        }
+
+        backdrop = {
+          left,
+          top,
+          width: width + labelPadding.width,
+          height: height + labelPadding.height,
+
+          color: optsAtIndex.backdropColor,
+        };
+      }
+
       items.push({
         rotation,
         label,
@@ -1236,7 +1280,8 @@ export default class Scale extends Element {
         textOffset,
         textAlign,
         textBaseline,
-        translation: [x, y]
+        translation: [x, y],
+        backdrop,
       });
     }
 
@@ -1466,6 +1511,12 @@ export default class Scale extends Element {
       const item = items[i];
       const tickFont = item.font;
       const label = item.label;
+
+      if (item.backdrop) {
+        ctx.fillStyle = item.backdrop.color;
+        ctx.fillRect(item.backdrop.left, item.backdrop.top, item.backdrop.width, item.backdrop.height);
+      }
+
       let y = item.textOffset;
       renderText(ctx, label, 0, y, tickFont, item);
     }

src/scales/scale.radialLinear.js

@@ -594,12 +594,6 @@ RadialLinearScale.defaults = {
     // Boolean - Show a backdrop to the scale label
     showLabelBackdrop: true,
 
-    // String - The colour of the label backdrop
-    backdropColor: 'rgba(255,255,255,0.75)',
-
-    // Number/Object - The backdrop padding of the label in pixels
-    backdropPadding: 2,
-
     callback: Ticks.formatters.numeric
   },
 

test/fixtures/core.scale/tick-backdrop.js

@@ -0,0 +1,76 @@
+const grid = {
+  display: false
+};
+const title = {
+  display: false,
+};
+module.exports = {
+  config: {
+    type: 'line',
+    options: {
+      events: [],
+      scales: {
+        top: {
+          type: 'linear',
+          position: 'top',
+          ticks: {
+            display: true,
+            showLabelBackdrop: true,
+            backdropColor: 'red',
+            backdropPadding: 5,
+            align: 'start',
+            crossAlign: 'near',
+          },
+          grid,
+          title
+        },
+        left: {
+          type: 'linear',
+          position: 'left',
+          ticks: {
+            display: true,
+            showLabelBackdrop: true,
+            backdropColor: 'green',
+            backdropPadding: 5,
+            crossAlign: 'center',
+          },
+          grid,
+          title
+        },
+        bottom: {
+          type: 'linear',
+          position: 'bottom',
+          ticks: {
+            display: true,
+            showLabelBackdrop: true,
+            backdropColor: 'blue',
+            backdropPadding: 5,
+            align: 'end',
+            crossAlign: 'far',
+          },
+          grid,
+          title
+        },
+        right: {
+          type: 'linear',
+          position: 'right',
+          ticks: {
+            display: true,
+            showLabelBackdrop: true,
+            backdropColor: 'gray',
+            backdropPadding: 5,
+          },
+          grid,
+          title
+        },
+      }
+    }
+  },
+  options: {
+    canvas: {
+      height: 256,
+      width: 256
+    },
+    spriteText: true,
+  }
+};

test/specs/scale.radialLinear.tests.js

@@ -36,8 +36,6 @@ describe('Test the radial linear scale', function() {
       ticks: {
         color: Chart.defaults.color,
         showLabelBackdrop: true,
-        backdropColor: 'rgba(255,255,255,0.75)',
-        backdropPadding: 2,
         callback: defaultConfig.ticks.callback
       },
 

types/index.esm.d.ts

@@ -2693,6 +2693,17 @@ export interface GridLineOptions {
 }
 
 export interface TickOptions {
+  /**
+   * Color of label backdrops.
+   * @default 'rgba(255, 255, 255, 0.75)'
+   */
+  backdropColor: Scriptable<Color, ScriptableScaleContext>;
+  /**
+   * Padding of tick backdrop.
+   * @default 2
+   */
+  backdropPadding: number | ChartArea;
+
   /**
    * Returns the string representation of the tick value as it should be displayed on the chart. See callback.
    */
@@ -2715,6 +2726,11 @@ export interface TickOptions {
    * Sets the offset of the tick labels from the axis
    */
   padding: number;
+  /**
+   * If true, draw a background behind the tick labels.
+   * @default false
+   */
+  showLabelBackdrop: Scriptable<boolean, ScriptableScaleContext>;
   /**
    * The color of the stroke around the text.
    * @default undefined
@@ -3116,17 +3132,6 @@ export type RadialLinearScaleOptions = CoreScaleOptions & {
   suggestedMin: number;
 
   ticks: TickOptions & {
-    /**
-     * Color of label backdrops.
-     * @default 'rgba(255, 255, 255, 0.75)'
-     */
-    backdropColor: Scriptable<Color, ScriptableScaleContext>;
-    /**
-     * Padding of label backdrop.
-     * @default 2
-     */
-    backdropPadding: number | ChartArea;
-
     /**
      * The Intl.NumberFormat options used by the default label formatter
      */
@@ -3152,12 +3157,6 @@ export type RadialLinearScaleOptions = CoreScaleOptions & {
      * User defined number of ticks
      */
     count: number;
-
-    /**
-     * If true, draw a background behind the tick labels.
-     * @default true
-     */
-    showLabelBackdrop: Scriptable<boolean, ScriptableScaleContext>;
   };
 };