watch-battery-optimization

watchOS Battery Optimization

Audit watchOS code for battery impact, with special focus on Always On Display (AOD) and TimelineView usage.

When to use this skill

• Before App Store submission
• After adding animations, timers, or sync logic
• When users report battery drain
• After changes to AOD behavior

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Step 1: AOD (Always On Display)

Requirement: When AOD is active (isLuminanceReduced == true), the UI should simplify but haptic feedback must still fire for segment changes. Do not disable haptics in AOD mode.

Check for:

• @Environment(\.isLuminanceReduced) usage
• Any conditional logic that disables haptics when dimmed

Suggested pattern:

@Environment(\.isLuminanceReduced) var isLuminanceReduced

// UI simplification
.animation(isLuminanceReduced ? nil : .default, value: state)

// Haptics should still run regardless of AOD
if shouldFireHaptic {
    haptics.play(pattern)
}

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Step 2: TimelineView & Timers

WATCH_DIR="YourApp Watch App"

# TimelineView usage
rg --type swift 'TimelineView' "$WATCH_DIR/"

# Periodic timeline (battery heavy)
rg --type swift 'TimelineView.*\.periodic' "$WATCH_DIR/"

# Timers
rg --type swift 'Timer\.' "$WATCH_DIR/"

Guidance:

• Prefer .animation schedules over .periodic
• Avoid tight timers (< 0.1s)
• Use .task { } to auto-cancel on view disappearance

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Step 3: Animation & GPU Cost

# Heavy animations
rg --type swift '\.animation\(|withAnimation|Canvas\s*\{|\.drawingGroup\(|\.blur\(' "$WATCH_DIR/Views/"

Guidance:

• Pause or simplify animations in AOD
• Avoid Canvas and heavy blur on watch

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Step 4: Background & Extended Runtime

rg --type swift 'WKExtendedRuntimeSession' "$WATCH_DIR/"

Guidance:

• Use only when necessary
• End sessions promptly

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Step 5: Energy Log Verification

Use Instruments → Energy Log to validate:

• No sustained high energy usage
• No excessive wakeups
• No continuous GPU usage

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Output Format