[Bug Fix]: Adjust tooltip position on StackedAreaChart when page is scrolled

packages/polaris-viz/src/components/StackedAreaChart/Chart.tsx

@@ -62,6 +62,7 @@ import {useStackedData} from './hooks';
 import {StackedAreas, Points} from './components';
 import {useStackedChartTooltipContent} from './hooks/useStackedChartTooltipContent';
 import {yAxisMinMax} from './utilities/yAxisMinMax';
+import {getAlteredStackedAreaChartPosition} from './utilities/getAlteredStackedAreaChartPosition';
 import styles from './Chart.scss';
 
 const TOOLTIP_POSITION: TooltipPositionOffset = {
@@ -382,6 +383,7 @@ export function Chart({
           focusElementDataType={DataType.Point}
           getMarkup={getTooltipMarkup}
           getPosition={getTooltipPosition}
+          getAlteredPosition={getAlteredStackedAreaChartPosition}
           id={tooltipId}
           margin={ChartMargin}
           onIndexChange={(index) => setActivePointIndex(index)}

packages/polaris-viz/src/components/StackedAreaChart/stories/ExternalTooltip.stories.tsx

@@ -0,0 +1,40 @@
+import type {Story} from '@storybook/react';
+
+export {META as default} from './meta';
+
+import {StackedAreaChart, type StackedAreaChartProps} from '../../../components';
+
+import {DEFAULT_DATA, DEFAULT_PROPS} from './data';
+
+function Card(args: StackedAreaChartProps) {
+  return (
+    <div
+      style={{
+        height: 500,
+        background: 'white',
+        borderRadius: '8px',
+        padding: 10,
+      }}
+    >
+      <StackedAreaChart {...args} theme="Uplift" />
+    </div>
+  );
+}
+
+const Template: Story<StackedAreaChartProps> = (args: StackedAreaChartProps) => {
+  return (
+    <div style={{overflowY: 'scroll', height:500}}>
+      <Card {...args} />
+      <div style={{height: 1500, width: 10}} />
+    </div>
+  );
+}
+
+
+
+export const ExternalTooltip: Story<StackedAreaChartProps> = Template.bind({});
+
+ExternalTooltip.args = {
+  ...DEFAULT_PROPS,
+  data: DEFAULT_DATA,
+};

packages/polaris-viz/src/components/StackedAreaChart/utilities/getAlteredStackedAreaChartPosition.ts

@@ -0,0 +1,54 @@
+import type {Dimensions} from '@shopify/polaris-viz-core';
+
+import type {TooltipPositionOffset} from '../../TooltipWrapper';
+import type {Margin} from '../../../types';
+
+// The space between the cursor and the tooltip
+const TOOLTIP_MARGIN = 20;
+
+export interface AlteredPositionProps {
+  bandwidth: number;
+  chartBounds: {x: number; y: number; width: number; height: number};
+  currentX: number;
+  currentY: number;
+  isPerformanceImpacted: boolean;
+  margin: Margin;
+  position: TooltipPositionOffset;
+  tooltipDimensions: Dimensions;
+}
+
+export interface AlteredPositionReturn {
+  x: number;
+  y: number;
+}
+
+export type AlteredPosition = (
+  props: AlteredPositionProps,
+) => AlteredPositionReturn;
+
+export function getAlteredStackedAreaChartPosition({
+  currentX,
+  currentY,
+  chartBounds,
+  margin,
+  tooltipDimensions,
+}: AlteredPositionProps): AlteredPositionReturn {
+  const x = Math.min(
+    Math.max(currentX, TOOLTIP_MARGIN),
+    chartBounds.width - tooltipDimensions.width - TOOLTIP_MARGIN,
+  );
+
+  // Y POSITIONING
+  // If y is below the chart, adjust the tooltip position to the bottom of the chart
+  //
+
+  const y =
+    currentY >= chartBounds.y + chartBounds.height
+      ? chartBounds.height -
+        tooltipDimensions.height -
+        TOOLTIP_MARGIN -
+        margin.Bottom
+      : currentY;
+
+  return {x, y};
+}

packages/polaris-viz/src/components/StackedAreaChart/utilities/tests/getAlteredStackedAreaChartPosition.test.ts

@@ -0,0 +1,80 @@
+import type {AlteredPositionProps} from '../../../TooltipWrapper';
+import {
+  TooltipVerticalOffset,
+  TooltipHorizontalOffset,
+} from '../../../TooltipWrapper';
+import {getAlteredStackedAreaChartPosition} from '../getAlteredStackedAreaChartPosition';
+
+const MARGIN = {Top: 0, Left: 0, Right: 0, Bottom: 0};
+const TOOLTIP_MARGIN = 20;
+
+const BASE_PROPS: AlteredPositionProps = {
+  isPerformanceImpacted: false,
+  chartBounds: {height: 100, width: 200, x: 0, y: 100},
+  tooltipDimensions: {height: 40, width: 60},
+  margin: MARGIN,
+  bandwidth: 40,
+  currentX: 20,
+  currentY: 0,
+  position: {
+    horizontal: TooltipHorizontalOffset.Left,
+    vertical: TooltipVerticalOffset.Center,
+  },
+};
+
+describe('getAlteredStackedAreaChartPosition', () => {
+  it('returns the original position of y when currentY is within the chart bounds', () => {
+    const props = {
+      ...BASE_PROPS,
+      currentX: 50,
+      currentY: 50,
+    };
+
+    const result = getAlteredStackedAreaChartPosition(props);
+
+    expect(result.x).toBe(50);
+    expect(result.y).toBe(50);
+  });
+
+  it('returns the adjusted position when currentY is greater than chartBounds.y + chartBounds.height', () => {
+    const props = {
+      ...BASE_PROPS,
+      currentY: 300,
+    };
+
+    const chartBounds = props.chartBounds;
+    const tooltipDimensions = props.tooltipDimensions;
+    const margin = props.margin;
+    const result = getAlteredStackedAreaChartPosition(props);
+
+    expect(result.x).toBe(20);
+
+    expect(result.y).toBe(
+      chartBounds.height -
+        tooltipDimensions.height -
+        TOOLTIP_MARGIN -
+        margin.Bottom,
+    );
+  });
+
+  it('returns the adjusted position when currentY is equal to chartBounds.y + chartBounds.height', () => {
+    const props = {
+      ...BASE_PROPS,
+      currentY: 200,
+    };
+
+    const chartBounds = props.chartBounds;
+    const tooltipDimensions = props.tooltipDimensions;
+    const margin = props.margin;
+    const result = getAlteredStackedAreaChartPosition(props);
+
+    expect(result.x).toBe(20);
+
+    expect(result.y).toBe(
+      chartBounds.height -
+        tooltipDimensions.height -
+        TOOLTIP_MARGIN -
+        margin.Bottom,
+    );
+  });
+});