feat: add projection click listener (#913)

This commits adds a projection click listener called onProjectionListener and available in the <Settings /> component with the following characteristics:
- it will fire every time the user clicks on the projection area (everything within the axes)
- the listener is called with an object that contains the nearest X and Ys values. These values are not screen coordinates but the real data domain values inverted computed inverting the x and y scales.
- we prevent the onProjectionListener from firing an event if a onElementClick listener is available and it has fired a click event

close #846

api/charts.api.md

@@ -1367,6 +1367,20 @@ export interface Postfixes {
     y1AccessorFormat?: string;
 }
 
+// @public
+export type ProjectedValues = {
+    x: PrimitiveValue;
+    y: Array<{
+        value: PrimitiveValue;
+        groupId: string;
+    }>;
+    smVerticalValue: PrimitiveValue;
+    smHorizontalValue: PrimitiveValue;
+};
+
+// @public
+export type ProjectionClickListener = (values: ProjectedValues) => void;
+
 // Warning: (ae-missing-release-tag) "RectAnnotation" is exported by the package, but it is missing a release tag (@alpha, @beta, @public, or @internal)
 //
 // @public (undocumented)
@@ -1605,6 +1619,7 @@ export interface SettingsSpec extends Spec {
     onLegendItemPlusClick?: LegendItemListener;
     // (undocumented)
     onPointerUpdate?: PointerUpdateListener;
+    onProjectionClick?: ProjectionClickListener;
     // (undocumented)
     onRenderChange?: RenderChangeListener;
     orderOrdinalBinsBy?: OrderBy;

src/chart_types/xy_chart/state/chart_state.tsx

@@ -47,7 +47,7 @@ import { isBrushingSelector } from './selectors/is_brushing';
 import { isChartEmptySelector } from './selectors/is_chart_empty';
 import { isTooltipVisibleSelector } from './selectors/is_tooltip_visible';
 import { createOnBrushEndCaller } from './selectors/on_brush_end_caller';
-import { createOnElementClickCaller } from './selectors/on_element_click_caller';
+import { createOnClickCaller } from './selectors/on_click_caller';
 import { createOnElementOutCaller } from './selectors/on_element_out_caller';
 import { createOnElementOverCaller } from './selectors/on_element_over_caller';
 import { createOnPointerMoveCaller } from './selectors/on_pointer_move_caller';
@@ -57,18 +57,19 @@ export class XYAxisChartState implements InternalChartState {
   chartType: ChartTypes;
   legendId: string;
 
-  onElementClickCaller: (state: GlobalChartState) => void;
+  onClickCaller: (state: GlobalChartState) => void;
   onElementOverCaller: (state: GlobalChartState) => void;
   onElementOutCaller: (state: GlobalChartState) => void;
   onBrushEndCaller: (state: GlobalChartState) => void;
   onPointerMoveCaller: (state: GlobalChartState) => void;
 
   constructor() {
-    this.onElementClickCaller = createOnElementClickCaller();
+    this.onClickCaller = createOnClickCaller();
     this.onElementOverCaller = createOnElementOverCaller();
     this.onElementOutCaller = createOnElementOutCaller();
     this.onBrushEndCaller = createOnBrushEndCaller();
     this.onPointerMoveCaller = createOnPointerMoveCaller();
+
     this.chartType = ChartTypes.XYAxis;
     this.legendId = htmlIdGenerator()('legend');
   }
@@ -145,7 +146,7 @@ export class XYAxisChartState implements InternalChartState {
   eventCallbacks(globalState: GlobalChartState) {
     this.onElementOverCaller(globalState);
     this.onElementOutCaller(globalState);
-    this.onElementClickCaller(globalState);
+    this.onClickCaller(globalState);
     this.onBrushEndCaller(globalState);
     this.onPointerMoveCaller(globalState);
   }

src/chart_types/xy_chart/state/selectors/get_cursor_pointer.ts

@@ -23,6 +23,7 @@ import { GlobalChartState } from '../../../../state/chart_state';
 import { getChartIdSelector } from '../../../../state/selectors/get_chart_id';
 import { getSettingsSpecSelector } from '../../../../state/selectors/get_settings_specs';
 import { computeChartDimensionsSelector } from './compute_chart_dimensions';
+import { getProjectedScaledValues } from './get_projected_scaled_values';
 import { getHighlightedGeomsSelector } from './get_tooltip_values_highlighted_geoms';
 import { isBrushAvailableSelector } from './is_brush_available';
 
@@ -34,10 +35,18 @@ export const getPointerCursorSelector = createCachedSelector(
     getHighlightedGeomsSelector,
     getSettingsSpecSelector,
     getCurrentPointerPositionSelector,
+    getProjectedScaledValues,
     computeChartDimensionsSelector,
     isBrushAvailableSelector,
   ],
-  (highlightedGeometries, settingsSpec, currentPointerPosition, { chartDimensions }, isBrushAvailable): string => {
+  (
+    highlightedGeometries,
+    settingsSpec,
+    currentPointerPosition,
+    projectedValues,
+    { chartDimensions },
+    isBrushAvailable,
+  ): string => {
     const { x, y } = currentPointerPosition;
     // get positions relative to chart
     const xPos = x - chartDimensions.left;
@@ -53,6 +62,9 @@ export const getPointerCursorSelector = createCachedSelector(
     if (highlightedGeometries.length > 0 && (settingsSpec.onElementClick || settingsSpec.onElementOver)) {
       return 'pointer';
     }
+    if (projectedValues !== null && settingsSpec.onProjectionClick) {
+      return 'pointer';
+    }
     return isBrushAvailable ? 'crosshair' : 'default';
   },
 )(getChartIdSelector);

src/chart_types/xy_chart/state/selectors/get_projected_scaled_values.ts

@@ -0,0 +1,54 @@
+/*
+ * Licensed to Elasticsearch B.V. under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch B.V. licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import createCachedSelector from 're-reselect';
+
+import { ProjectedValues } from '../../../../specs/settings';
+import { getChartIdSelector } from '../../../../state/selectors/get_chart_id';
+import { computeSeriesGeometriesSelector } from './compute_series_geometries';
+import { getGeometriesIndexKeysSelector } from './get_geometries_index_keys';
+import { getOrientedProjectedPointerPositionSelector } from './get_oriented_projected_pointer_position';
+
+/** @internal */
+export const getProjectedScaledValues = createCachedSelector(
+  [getOrientedProjectedPointerPositionSelector, computeSeriesGeometriesSelector, getGeometriesIndexKeysSelector],
+  (
+    { x, y, verticalPanelValue, horizontalPanelValue },
+    { scales: { xScale, yScales } },
+    geometriesIndexKeys,
+  ): ProjectedValues | undefined => {
+    if (!xScale) {
+      return;
+    }
+
+    const xValue = xScale.invertWithStep(x, geometriesIndexKeys);
+    if (!xValue) {
+      return;
+    }
+
+    return {
+      x: xValue.value,
+      y: [...yScales.entries()].map(([groupId, yScale]) => {
+        return { value: yScale.invert(y), groupId };
+      }),
+      smVerticalValue: verticalPanelValue,
+      smHorizontalValue: horizontalPanelValue,
+    };
+  },
+)(getChartIdSelector);

src/chart_types/xy_chart/state/selectors/on_element_click_caller.ts → src/chart_types/xy_chart/state/selectors/on_click_caller.ts

@@ -21,13 +21,15 @@ import createCachedSelector from 're-reselect';
 import { Selector } from 'reselect';
 
 import { ChartTypes } from '../../..';
-import { SettingsSpec } from '../../../../specs';
+import { ProjectedValues, SettingsSpec } from '../../../../specs';
 import { GlobalChartState, PointerState } from '../../../../state/chart_state';
+import { getChartIdSelector } from '../../../../state/selectors/get_chart_id';
 import { getLastClickSelector } from '../../../../state/selectors/get_last_click';
 import { getSettingsSpecSelector } from '../../../../state/selectors/get_settings_specs';
 import { isClicking } from '../../../../state/utils';
 import { IndexedGeometry, GeometryValue } from '../../../../utils/geometry';
 import { XYChartSeriesIdentifier } from '../../utils/series';
+import { getProjectedScaledValues } from './get_projected_scaled_values';
 import { getHighlightedGeomsSelector } from './get_tooltip_values_highlighted_geoms';
 
 /**
@@ -37,33 +39,62 @@ import { getHighlightedGeomsSelector } from './get_tooltip_values_highlighted_ge
  * - the pointer state goes from down state to up state
  * @internal
  */
-export function createOnElementClickCaller(): (state: GlobalChartState) => void {
+export function createOnClickCaller(): (state: GlobalChartState) => void {
   let prevClick: PointerState | null = null;
   let selector: Selector<GlobalChartState, void> | null = null;
   return (state: GlobalChartState) => {
-    if (selector === null && state.chartType === ChartTypes.XYAxis) {
-      selector = createCachedSelector(
-        [getLastClickSelector, getSettingsSpecSelector, getHighlightedGeomsSelector],
-        (lastClick: PointerState | null, settings: SettingsSpec, indexedGeometries: IndexedGeometry[]): void => {
-          if (!settings.onElementClick) {
-            return;
-          }
-          if (indexedGeometries.length > 0 && isClicking(prevClick, lastClick)) {
-            if (settings && settings.onElementClick) {
-              const elements = indexedGeometries.map<[GeometryValue, XYChartSeriesIdentifier]>(
-                ({ value, seriesIdentifier }) => [value, seriesIdentifier],
-              );
-              settings.onElementClick(elements);
-            }
-          }
-          prevClick = lastClick;
-        },
-      )({
-        keySelector: (state: GlobalChartState) => state.chartId,
-      });
-    }
     if (selector) {
-      selector(state);
+      return selector(state);
+    }
+    if (state.chartType !== ChartTypes.XYAxis) {
+      return;
     }
+    selector = createCachedSelector(
+      [getLastClickSelector, getSettingsSpecSelector, getHighlightedGeomsSelector, getProjectedScaledValues],
+      (
+        lastClick: PointerState | null,
+        { onElementClick, onProjectionClick }: SettingsSpec,
+        indexedGeometries: IndexedGeometry[],
+        values,
+      ): void => {
+        if (!isClicking(prevClick, lastClick)) {
+          return;
+        }
+        const elementClickFired = tryFiringOnElementClick(indexedGeometries, onElementClick);
+        if (!elementClickFired) {
+          tryFiringOnProjectionClick(values, onProjectionClick);
+        }
+        prevClick = lastClick;
+      },
+    )({
+      keySelector: getChartIdSelector,
+    });
   };
 }
+
+function tryFiringOnElementClick(
+  indexedGeometries: IndexedGeometry[],
+  onElementClick: SettingsSpec['onElementClick'],
+): boolean {
+  if (indexedGeometries.length === 0 || !onElementClick) {
+    return false;
+  }
+
+  const elements = indexedGeometries.map<[GeometryValue, XYChartSeriesIdentifier]>(({ value, seriesIdentifier }) => [
+    value,
+    seriesIdentifier,
+  ]);
+  onElementClick(elements);
+  return true;
+}
+
+function tryFiringOnProjectionClick(
+  values: ProjectedValues | undefined,
+  onProjectionClick: SettingsSpec['onProjectionClick'],
+): boolean {
+  if (values === undefined || !onProjectionClick) {
+    return false;
+  }
+  onProjectionClick(values);
+  return true;
+}

src/specs/settings.tsx

@@ -55,6 +55,38 @@ export type XYChartElementEvent = [GeometryValue, XYChartSeriesIdentifier];
 export type PartitionElementEvent = [Array<LayerValue>, SeriesIdentifier];
 export type HeatmapElementEvent = [Cell, SeriesIdentifier];
 
+/**
+ * @public
+ * An object that contains the scaled mouse position based on
+ * the current chart configuration.
+ */
+export type ProjectedValues = {
+  /**
+   * The independent variable of the chart
+   */
+  x: PrimitiveValue;
+  /**
+   * The set of dependent variable, each one with its own groupId
+   */
+  y: Array<{ value: PrimitiveValue; groupId: string }>;
+  /**
+   * The categorical value used for the vertical placement of the chart
+   * in a small multiple layout
+   */
+  smVerticalValue: PrimitiveValue;
+  /**
+   * The categorical value used for the horizontal placement of the chart
+   * in a small multiple layout
+   */
+  smHorizontalValue: PrimitiveValue;
+};
+
+/**
+ * @public
+ * The listener type for click on the projection area.
+ */
+export type ProjectionClickListener = (values: ProjectedValues) => void;
+
 export type ElementClickListener = (
   elements: Array<XYChartElementEvent | PartitionElementEvent | HeatmapElementEvent>,
 ) => void;
@@ -77,7 +109,7 @@ export interface BasePointerEvent {
   type: PointerEventType;
 }
 /**
- * Event used to syncronize pointers/mouse positions between Charts.
+ * Event used to synchronize pointers/mouse positions between Charts.
  *
  * fired as callback argument for `PointerUpdateListener`
  */
@@ -328,6 +360,12 @@ export interface SettingsSpec extends Spec {
    * Compares title, position and first & last tick labels
    */
   hideDuplicateAxes: boolean;
+  /**
+   * Attach a listener for click on the projection area.
+   * The listener will be called with the current x value snapped to the closest
+   * X axis point, and an array of Y values for every groupId used in the chart.
+   */
+  onProjectionClick?: ProjectionClickListener;
   onElementClick?: ElementClickListener;
   onElementOver?: ElementOverListener;
   onElementOut?: BasicListener;

stories/interactions/1_bar_clicks.tsx

@@ -27,6 +27,7 @@ const onElementListeners = {
   onElementClick: action('onElementClick'),
   onElementOver: action('onElementOver'),
   onElementOut: action('onElementOut'),
+  onProjectionClick: action('onProjectionClick'),
 };
 
 export const Example = () => {