[Fix]: Markers are too big in LineChart and ScatterChart

[singlayush]

Fix marker sizing in LineChart and ScatterChart

Problem

Markers in LineChart and ScatterChart were rendering too large compared to expected behavior (e.g., Plotly). The previous formula (markerSize * extraMaxPixels) / maxMarkerSize would essentially result in scaling markers based on the extraMaxPixels. But we would only want to scale down and not scale up. The scaling down is needed to ensure there is no overflow out of the chart, while scaling up serves no purpose and results in too big markers.

Solution

Updated the marker radius calculation to use conditional logic:

extraMaxPixels > maxMarkerSize 
  ? markerSize 
  : (markerSize * extraMaxPixels) / maxMarkerSize

Logic:

• If extraMaxPixels > maxMarkerSize: Use the actual markerSize directly (enough space available)
• Otherwise: Scale down proportionally to fit within available space

Test Run: https://github.com/microsoft/fluentui-charting-contrib/actions/runs/21618414015

Examples

markerSize	extraMaxPixels	maxMarkerSize	Result
100	10	100	10 (extra < max, scaled down significantly: 100 × 10 / 100)
2	100	2	2 (extra > max, use markerSize directly no scaling needed)
20	25	30	16.67 (extra < max, scaled down slightly: 20 × 25 / 30)

Changes

• LineChart.tsx: Updated all 4 marker radius calculations to use consistent formula
• ScatterChart.tsx: Updated marker radius calculation with same formula
• Z-order fix: Markers now render on top of lines (LineChart)

Screenshots

Before

### Plotly ### After ### Before ### Plotly ### After

Before

### Plotly

Plotly

### After

Before

### Plotly ### After

Testing

• Verified with single data point
• Verified with multiple data points (similar marker sizes)
• Verified with varying marker sizes
• Verified markers appear above lines

[github-actions]

📊 Bundle size report

Package & Exports	Baseline (minified/GZIP)	PR	Change
react-charts DeclarativeChart	756.617 kB 217.631 kB	757.246 kB 217.857 kB	629 B 226 B
react-charts LineChart	417.347 kB 126.389 kB	417.931 kB 126.603 kB	584 B 214 B
react-charts ScatterChart	397.174 kB 120.59 kB	397.499 kB 120.721 kB	325 B 131 B

Unchanged fixtures

Package & Exports	Size (minified/GZIP)
react-charts AreaChart	406.783 kB 124.495 kB
react-charts DonutChart	317.224 kB 94.361 kB
react-charts FunnelChart	308.774 kB 91.361 kB
react-charts GanttChart	389.926 kB 118.05 kB
react-charts GaugeChart	316.655 kB 93.799 kB
react-charts GroupedVerticalBarChart	397.772 kB 120.667 kB
react-charts HeatMapChart	391.973 kB 119.859 kB
react-charts HorizontalBarChart	296.951 kB 86.138 kB
react-charts HorizontalBarChartWithAxis	63 B 83 B
react-charts Legends	235.905 kB 69.363 kB
react-charts PolarChart	345.84 kB 105.418 kB
react-charts SankeyChart	213.881 kB 65.62 kB
react-charts Sparkline	91.393 kB 28.708 kB
react-charts VerticalBarChart	434.249 kB 126.27 kB
react-charts VerticalStackedBarChart	403.686 kB 121.535 kB

_{🤖 This report was generated against 16db0e6234dd1ad6cb234333b75d55f42a85b1c6}

[github-actions]

Pull request demo site: URL

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[AtishayMsft]

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