136 lines
6.1 KiB
Markdown
136 lines
6.1 KiB
Markdown
# Swift Charts Accessibility, Fallback, and Resources
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## Table of Contents
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- [Accessibility](#accessibility)
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- [Meaningful Labels](#meaningful-labels)
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- [Custom Audio Graphs](#custom-audio-graphs)
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- [Composite Example](#composite-example)
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- [Fallback Strategies](#fallback-strategies)
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- [Version Breakdown](#version-breakdown)
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- [WWDC Sessions](#wwdc-sessions)
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- [Summary Checklist](#summary-checklist)
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---
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## Accessibility
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Swift Charts provides built-in accessibility support. VoiceOver users get three rotor actions automatically:
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- **Describe Chart** — overview of axes and data series
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- **Audio Graph** — sonification where pitch represents data values
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- **Chart Detail** — interactive mode for exploring individual data points
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### Meaningful Labels
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**Always** use clear, descriptive strings in `.value(_, _)` calls. These labels are read by VoiceOver and used in the Audio Graph.
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```swift
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// Good — descriptive labels
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LineMark(
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x: .value("Date", entry.date),
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y: .value("Daily Steps", entry.count)
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)
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// Bad — generic labels
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LineMark(
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x: .value("X", entry.date),
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y: .value("Y", entry.count)
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)
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```
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### Custom Audio Graphs
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For advanced accessibility, conform your chart view to `AXChartDescriptorRepresentable` and implement `makeChartDescriptor()`. Attach it with `.accessibilityChartDescriptor(self)`.
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```swift
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struct StepsChart: View, AXChartDescriptorRepresentable {
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let steps: [DailySteps]
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var body: some View {
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Chart(steps) { day in
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LineMark(x: .value("Date", day.date), y: .value("Steps", day.count))
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}
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.accessibilityChartDescriptor(self)
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}
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func makeChartDescriptor() -> AXChartDescriptor {
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guard let first = steps.first, let last = steps.last else {
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return AXChartDescriptor(title: "Daily Step Count", summary: nil,
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xAxis: AXNumericDataAxisDescriptor(title: "Date", range: 0...1, gridlinePositions: []) { "\($0)" },
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yAxis: AXNumericDataAxisDescriptor(title: "Steps", range: 0...1, gridlinePositions: []) { "\($0)" },
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additionalAxes: [], series: [])
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}
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let xAxis = AXDateDataAxisDescriptor(
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title: "Date", range: first.date...last.date, gridlinePositions: [])
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let yAxis = AXNumericDataAxisDescriptor(
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title: "Steps", range: 0...Double(steps.map(\.count).max() ?? 0),
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gridlinePositions: []) { "\(Int($0)) steps" }
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let series = AXDataSeriesDescriptor(
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name: "Daily Steps", isContinuous: true,
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dataPoints: steps.map { .init(x: $0.date, y: Double($0.count)) })
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return AXChartDescriptor(title: "Daily Step Count", summary: nil,
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xAxis: xAxis, yAxis: yAxis, additionalAxes: [], series: [series])
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}
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}
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```
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## Composite Example
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A scrollable bar chart with range selection combining multiple iOS 17+ APIs:
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```swift
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@State private var selectedRange: ClosedRange<Int>?
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Chart(weeklyRevenue) { week in
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BarMark(x: .value("Week", week.index), y: .value("Revenue", week.revenue))
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.foregroundStyle(by: .value("Region", week.region))
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}
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.chartScrollableAxes(.horizontal)
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.chartXVisibleDomain(length: 8)
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.chartXSelection(range: $selectedRange)
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.chartXAxis {
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AxisMarks(values: .stride(by: 1)) {
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AxisGridLine()
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AxisValueLabel { Text("W\($0.as(Int.self) ?? 0)") }
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}
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}
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```
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## Fallback Strategies
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Gate advanced APIs with `#available` and provide a fallback chart without the gated features. Because chart modifiers like `.chartXSelection` change the return type, you must duplicate the entire `Chart` — you cannot conditionally apply the modifier:
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### Version Breakdown
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- iOS 16+: `Chart`, custom axes, scales, `BarMark`, `LineMark`, `AreaMark`, `PointMark`, `RectangleMark`, `RuleMark`, `ChartProxy`, `chartOverlay`, `chartBackground`
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- iOS 17+: `SectorMark`, `chartXSelection`, `chartYSelection`, `chartAngleSelection`, `chartScrollableAxes`, visible-domain scrolling APIs, `chartGesture`
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- iOS 18+: `AreaPlot`, `BarPlot`, `LinePlot`, `PointPlot`, `RectanglePlot`, `RulePlot`, `SectorPlot`, function plotting
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- iOS 26+: `Chart3D`, `SurfacePlot`, Z-axis marks, 3D camera and pose APIs
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## WWDC Sessions
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- [Hello Swift Charts](https://developer.apple.com/videos/play/wwdc2022/10136/) (WWDC 2022) — introduction to the framework
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- [Swift Charts: Raise the bar](https://developer.apple.com/videos/play/wwdc2022/10137/) (WWDC 2022) — marks, composition, customization
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- [Design an effective chart](https://developer.apple.com/videos/play/wwdc2022/110340/) (WWDC 2022) — chart design principles
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- [Design app experiences with charts](https://developer.apple.com/videos/play/wwdc2022/110342/) (WWDC 2022) — integrating charts into app UX
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- [Explore pie charts and interactivity in Swift Charts](https://developer.apple.com/videos/play/wwdc2023/10037/) (WWDC 2023) — SectorMark, selection, scrolling
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- [Swift Charts: Vectorized and function plots](https://developer.apple.com/videos/play/wwdc2024/10155/) (WWDC 2024) — LinePlot, AreaPlot, function plotting
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- [Bring Swift Charts to the third dimension](https://developer.apple.com/videos/play/wwdc2025/313/) (WWDC 2025) — Chart3D, SurfacePlot, 3D marks
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## Summary Checklist
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- [ ] `import Charts` is present in files using chart types
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- [ ] Deployment target matches the APIs used (`Chart` on iOS 16+, selection and `SectorMark` on iOS 17+, plot types on iOS 18+, `Chart3D` on iOS 26+)
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- [ ] Chart data models use `Identifiable` (or `Chart(data, id:)` is provided)
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- [ ] All chart families are represented with the correct mark type
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- [ ] Axes use `AxisMarks` when default ticks are too dense or unclear
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- [ ] `chartXScale` or `chartYScale` is set when fixed domains matter
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- [ ] Chart-wide modifiers are applied to `Chart`, not individual marks
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- [ ] `foregroundStyle(by:)` used for categorical series (not manual per-mark colors)
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- [ ] Single-value selection uses `chartXSelection(value:)` or `chartYSelection(value:)`
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- [ ] Range selection uses `chartXSelection(range:)` or `chartYSelection(range:)`
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- [ ] `SectorMark` selection uses `chartAngleSelection(value:)`
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- [ ] iOS 17+, iOS 18+, and iOS 26+ APIs are guarded with `#available`
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- [ ] `.value()` labels are descriptive for VoiceOver and Audio Graph accessibility
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