axiom-sf-symbols（公理 SF 符号）

SF Symbols — Effects, Rendering, and Custom Symbols

When to Use This Skill

Use when:

• Choosing between rendering modes (Monochrome, Hierarchical, Palette, Multicolor)
• Implementing symbol effects or animations (Bounce, Pulse, Scale, Wiggle, Rotate, Breathe, Draw)
• Working with SF Symbols 7 Draw On/Off animations
• Creating custom symbols in the SF Symbols app
• Troubleshooting symbol colors, effects not playing, or weight mismatches
• Deciding which effect matches a specific UX purpose
• Handling accessibility with symbol animations (Reduce Motion)

Related Skills

• Use axiom-sf-symbols-ref for complete API reference with all modifiers, UIKit equivalents, and platform availability matrix
• Use axiom-swiftui-animation-ref for general SwiftUI animation (not symbol-specific)
• Use axiom-hig-ref for broader icon design guidelines

Example Prompts

1. "My SF Symbol shows as a single flat color but I want it to have depth with multiple shades. How do I fix this?"

The skill covers rendering mode selection — Hierarchical for depth from a single color, Palette for explicit per-layer colors

2. "I want my download button to animate when tapped, then show a spinning indicator while downloading, and animate to a checkmark when done."

The skill covers effect selection: Bounce for tap feedback, Breathe/Pulse for in-progress, Replace with content transition for completion

3. "I'm trying to use the new Draw animations from SF Symbols 7 but the effect isn't playing."

The skill covers Draw On/Off implementation, playback modes, iOS 26 requirements, and common troubleshooting

4. "How do I create a custom symbol that supports all rendering modes and the new Draw animation?"

The skill covers custom symbol authoring workflow, template layers, Draw annotation with guide points

Part 1: Rendering Mode Decision Tree

SF Symbols support 4 rendering modes. The right choice depends on your design intent.

Quick Decision

Need depth from ONE color?           → Hierarchical
Need specific colors per layer?      → Palette
Want Apple's curated colors?         → Multicolor
Just need a tinted icon?             → Monochrome (default)

Monochrome

The default mode. Every layer renders in the same color (your foregroundStyle).

Image(systemName: "cloud.rain.fill")
    .foregroundStyle(.blue)
// All layers are blue

When to use: Simple tinted icons, matching text color, toolbar items, tab bar items.

Hierarchical

Renders layers at different opacities derived from a single color. Primary layers are fully opaque; secondary and tertiary layers get progressively more transparent. Creates depth without specifying multiple colors.

Image(systemName: "cloud.rain.fill")
    .symbolRenderingMode(.hierarchical)
    .foregroundStyle(.blue)
// Cloud is full blue, rain drops are lighter blue

When to use: When you want visual depth but still want the icon to feel cohesive with a single hue. Most common choice for polished UI.

Palette

Each layer gets an explicit color. Unlike Hierarchical, no automatic opacity derivation — you control each layer's color directly.

Image(systemName: "cloud.rain.fill")
    .symbolRenderingMode(.palette)
    .foregroundStyle(.blue, .cyan)
// Cloud is blue, rain drops are cyan

When to use: Branded icons, status indicators where specific colors carry meaning, designs requiring exact color control.

Gotcha: If you provide fewer colors than layers, extra layers reuse the last color. If the symbol has 3 layers and you provide 2 colors, the third layer uses the second color.

Multicolor

Uses Apple's predefined color scheme for each symbol. Colors are fixed — you cannot customize them.

Image(systemName: "cloud.rain.fill")
    .symbolRenderingMode(.multicolor)
// Cloud is white, rain drops are blue (Apple's design)

When to use: Weather indicators, file type icons, or anywhere Apple's curated design intent matches your needs. Not all symbols support Multicolor — unsupported symbols fall back to Monochrome.

Common Mistakes

Part 2: Symbol Effects System

Symbol effects bring SF Symbols to life with motion. Every effect falls into one of four behavioral categories.

Effect Categories

Which Effect for Which UX Purpose

User tapped something               → Bounce (discrete)
Something changed, draw attention    → Wiggle (discrete, iOS 18+)
Ongoing process/loading              → Pulse, Breathe, or Variable Color (indefinite)
Rotation indicates progress          → Rotate (indefinite, iOS 18+)
Show/hide symbol                     → Appear/Disappear (transition)
Swap between two symbols             → Replace (content transition)
Symbol enters with hand-drawn style  → Draw On (iOS 26+)
Symbol exits with hand-drawn style   → Draw Off (iOS 26+)
Progress indicator along path        → Variable Draw (iOS 26+)
Scale up/down for emphasis           → Scale (indefinite)

Discrete Effects

Fire once when a value changes. The symbol performs the animation and returns to its resting state.

Bounce

The most common discrete effect. A brief, springy animation.

@State private var downloadCount = 0

Image(systemName: "arrow.down.circle")
    .symbolEffect(.bounce, value: downloadCount)

The animation triggers each time downloadCount changes.

Directional options: .bounce.up, .bounce.down

Wiggle (iOS 18+)

A horizontal shake that draws attention to the symbol.

Image(systemName: "bell.fill")
    .symbolEffect(.wiggle, value: notificationCount)

Directional options: .wiggle.left, .wiggle.right, .wiggle.forward, .wiggle.backward

.forward and .backward respect reading direction — use these for RTL support.

Rotate (as Discrete, iOS 18+)

A single rotation when triggered by value change.

Image(systemName: "arrow.trianglehead.2.clockwise")
    .symbolEffect(.rotate, value: refreshCount)

Options: .rotate.clockwise, .rotate.counterClockwise

By Layer: Some symbols rotate only specific layers (e.g., fan blades spin but the housing stays fixed). Use .rotate.byLayer to activate this.

Indefinite Effects

Run continuously while isActive is true. Stop when isActive becomes false.

Pulse

A subtle opacity pulse. Good for "waiting" states.

Image(systemName: "network")
    .symbolEffect(.pulse, isActive: isConnecting)

Variable Color

Iterates through the symbol's layers, highlighting each in sequence. Creates a "filling up" or "cycling" look.

Image(systemName: "wifi")
    .symbolEffect(.variableColor.iterative, isActive: isSearching)

Variants:

• .variableColor.iterative — highlights one layer at a time
• .variableColor.cumulative — progressively fills layers
• .variableColor.reversing — cycles back and forth
• Combine: .variableColor.iterative.reversing

Scale

Scales the symbol up or down.

Image(systemName: "mic.fill")
    .symbolEffect(.scale.up, isActive: isRecording)

Breathe (iOS 18+)

A smooth, rhythmic scale animation — like the symbol is breathing.

Image(systemName: "heart.fill")
    .symbolEffect(.breathe, isActive: isMonitoring)

Variants: .breathe.plain (scale only), .breathe.pulse (scale + opacity)

Rotate (as Indefinite, iOS 18+)

Continuous rotation for processing indicators.

Image(systemName: "gear")
    .symbolEffect(.rotate, isActive: isProcessing)

Effect Options

All effects accept SymbolEffectOptions via the options parameter.

// Repeat 3 times
.symbolEffect(.bounce, options: .repeat(3), value: count)

// Double speed
.symbolEffect(.pulse, options: .speed(2.0), isActive: true)

// Repeat continuously
.symbolEffect(.variableColor, options: .repeat(.continuous), isActive: true)

// Non-repeating (run once)
.symbolEffect(.breathe, options: .nonRepeating, isActive: true)

// Combine options
.symbolEffect(.bounce, options: .repeat(5).speed(1.5), value: count)

Transition Effects

Used when a symbol-based view appears or disappears from the view hierarchy.

if showSymbol {
    Image(systemName: "checkmark.circle.fill")
        .transition(.symbolEffect(.appear))
}

Available transitions: .appear, .disappear

Variants: .appear.up, .appear.down, .disappear.up, .disappear.down

Content Transitions

Used to animate from one symbol to another. Applied to the container, not the symbol.

@State private var isFavorite = false

Button {
    isFavorite.toggle()
} label: {
    Image(systemName: isFavorite ? "star.fill" : "star")
        .contentTransition(.symbolEffect(.replace))
}

Replace variants:

• .replace.downUp — old symbol moves down, new moves up
• .replace.upUp — both move up
• .replace.offUp — old fades off, new moves up

Magic Replace

When two symbols share a common structure (like star and star.fill, or pause.fill and play.fill), Replace automatically performs a Magic Replace — morphing shared elements while transitioning differing parts. Magic Replace is the default behavior for .replace in iOS 18+. For explicit control:

// Explicit Magic Replace with fallback
.contentTransition(.symbolEffect(.replace.magic(fallback: .replace.downUp)))

Part 3: SF Symbols 7 — Draw Animations (iOS 26+)

Draw animations simulate the natural flow of drawing a symbol with a pen. This is the signature new feature in SF Symbols 7.

Draw On and Draw Off

Draw On animates a symbol appearing by "drawing" it stroke by stroke. Draw Off animates a symbol disappearing by "erasing" it.

// Draw On — symbol draws in when isComplete becomes true
Image(systemName: "checkmark.circle")
    .symbolEffect(.drawOn, isActive: isComplete)

// Draw Off — symbol draws out when isHidden becomes true
Image(systemName: "star.fill")
    .symbolEffect(.drawOff, isActive: isHidden)

Playback Modes

Control how multi-layer symbols animate their draw:

// By Layer (default) — staggered timing, layers overlap
Image(systemName: "square.and.arrow.up")
    .symbolEffect(.drawOn.byLayer, isActive: showIcon)

// Whole Symbol — all layers draw simultaneously
Image(systemName: "square.and.arrow.up")
    .symbolEffect(.drawOn.wholeSymbol, isActive: showIcon)

// Individually — sequential, each layer completes before next starts
Image(systemName: "square.and.arrow.up")
    .symbolEffect(.drawOn.individually, isActive: showIcon)

When to use each mode:

• By Layer (default): Most natural feel, good for most symbols
• Whole Symbol: When the symbol should appear as one unit, not in parts
• Individually: When you want to emphasize each layer separately (storytelling, onboarding)

Draw Off Direction

Draw Off supports controlling whether the animation plays forward or in reverse:

// Forward (default) — follows the draw path
.symbolEffect(.drawOff.nonReversed, isActive: isHidden)

// Reversed — erases in reverse order of how it was drawn
.symbolEffect(.drawOff.reversed, isActive: isErasing)

Variable Draw

Variable Draw uses SymbolVariableValueMode.draw to partially draw a symbol's stroke path based on a 0.0 to 1.0 value — perfect for progress indicators.

Image(systemName: "thermometer.high", variableValue: temperature)
    .symbolVariableValueMode(.draw) // iOS 26+

Compare with traditional Variable Color (which sets opacity per layer):

Image(systemName: "wifi", variableValue: signalStrength)
    .symbolVariableValueMode(.color) // iOS 17+ (default behavior)

Constraint: A symbol can support both Variable Color and Variable Draw, but only one mode can be active at render time. Setting an unsupported mode has no visible effect.

Gradient Rendering

SF Symbols 7 introduces SymbolColorRenderingMode for gradient fills generated from a single source color.

Image(systemName: "star.fill")
    .symbolColorRenderingMode(.gradient) // iOS 26+
    .foregroundStyle(.red)

Gradients work with all rendering modes and are most effective at larger sizes.

Magic Replace with Draw

When using .contentTransition(.symbolEffect(.replace)) between certain symbol pairs, the system now combines Draw Off on the outgoing symbol with Draw On for the incoming symbol. The enclosure (if shared, like a circle outline) is preserved while inner elements transition with draw animations.

// Automatic Draw-enhanced Magic Replace
Image(systemName: isComplete ? "checkmark.circle.fill" : "circle")
    .contentTransition(.symbolEffect(.replace))

Custom Symbol Draw Annotation

To enable Draw animations on custom symbols, annotate paths in the SF Symbols app:

1. Open your custom symbol in SF Symbols 7
2. Select a path layer
3. Add guide points to define draw direction:

- Start point (open circle): Where drawing begins - End point (closed circle): Where drawing ends - Corner point (diamond): Sharp direction changes - Bidirectional point: Enables center-outward drawing - Attachment point: Connects non-drawing decorative elements

1. Minimum: Two guide points per path (start and end)
2. Test using the Preview panel in SF Symbols app

Option-drag guide points for precise placement. Use context menus to configure direction and end caps.

Part 4: Anti-Patterns

Wrong Rendering Mode

Wrong Effect Choice

Missing iOS Version Checks

// ❌ Crashes on iOS 17
Image(systemName: "bell")
    .symbolEffect(.wiggle, value: count) // Wiggle requires iOS 18+

// ✅ Safe version check
Image(systemName: "bell")
    .modifier(BellEffectModifier(count: count))

struct BellEffectModifier: ViewModifier {
    let count: Int
    func body(content: Content) -> some View {
        if #available(iOS 18, *) {
            content.symbolEffect(.wiggle, value: count)
        } else {
            content.symbolEffect(.bounce, value: count)
        }
    }
}

Ignoring Reduce Motion

Symbol effects automatically respect the Reduce Motion accessibility setting — most effects are suppressed or simplified. However, if you're using effects to convey essential information (not just decoration), provide an alternative:

// Variable Color conveys WiFi strength — provide text fallback
Image(systemName: "wifi")
    .symbolEffect(.variableColor, isActive: isSearching)
    .accessibilityLabel("Searching for WiFi networks")

Do not disable Reduce Motion or try to force-play effects. The system handles this correctly.

Missing Accessibility Labels

// ❌ VoiceOver says "star.fill"
Image(systemName: "star.fill")

// ✅ VoiceOver says "Favorite"
Image(systemName: "star.fill")
    .accessibilityLabel("Favorite")

When using .contentTransition(.symbolEffect(.replace)) to swap symbols, update the accessibility label to match the current state:

Image(systemName: isFavorite ? "star.fill" : "star")
    .contentTransition(.symbolEffect(.replace))
    .accessibilityLabel(isFavorite ? "Remove from favorites" : "Add to favorites")

Part 5: Troubleshooting

Effect Not Playing

Symptom: .symbolEffect() modifier applied but no animation visible.

1. Check iOS version — Bounce/Pulse/Scale require iOS 17+, Wiggle/Rotate/Breathe require iOS 18+, Draw requires iOS 26+
2. Check Reduce Motion — Settings > Accessibility > Motion > Reduce Motion. If on, most effects are suppressed
3. Check trigger type — Discrete effects need value: that changes. Indefinite effects need isActive: true. Transition effects need the view to actually enter/leave the hierarchy
4. Check symbol compatibility — Not all symbols support all effects. Open the SF Symbols app, select the symbol, and check the Animation inspector
5. Check for conflicting effects — Multiple .symbolEffect() modifiers on the same view can conflict. Use a single effect or combine with options

Wrong Colors in Rendering Mode

Symptom: Symbol colors don't match expected appearance.

1. Check rendering mode — If you set .foregroundStyle but see only one color, you may need .symbolRenderingMode(.palette) or .hierarchical
2. Check .tint vs .foregroundStyle — In UIKit, tintColor affects Monochrome and Hierarchical. For Palette, use UIImage.SymbolConfiguration(paletteColors:)
3. Check Multicolor support — Not all symbols have Multicolor variants. Unsupported symbols fall back to Monochrome
4. Check environment — .foregroundStyle from a parent view may override your rendering mode. Apply .symbolRenderingMode() directly on the Image

Custom Symbol Weight Mismatch

Symptom: Custom symbol looks too thin or too thick next to text or other symbols.

1. Check template weight — Custom symbols need weight variants matching the 9 SF Pro weights. Export from SF Symbols app handles this
2. Check .font() alignment — The symbol's weight follows the applied font weight. If using .font(.title), ensure your custom symbol has appropriate weight variants
3. Check scale — .imageScale(.small/.medium/.large) affects overall size. Use .font() for weight matching

Draw Animation Not Working on Custom Symbol

Symptom: .symbolEffect(.drawOn) applied to custom symbol but no draw animation occurs.

1. Check guide points — Custom symbols need Draw annotation with at least 2 guide points per path (start + end)
2. Check SF Symbols app version — Draw annotation requires SF Symbols 7+
3. Check path structure — Guide points must be placed on stroked paths, not fills. Convert fills to strokes where draw animation is desired
4. Check layer structure — Each annotatable layer needs its own guide points

Part 6: Pressure Scenarios

Scenario 1: "Just use a static image, symbols are overkill"

Setup: Designer provides PNG icons. Developer considers using them instead of SF Symbols.

Why this matters: Static PNGs don't adapt to Dynamic Type, Bold Text, Dark Mode, or accessibility settings. They also don't support symbol effects.

Professional response: "SF Symbols scale with text, support 9 weights, adapt to Dark Mode and Bold Text automatically, and enable animations without custom code. A PNG requires @1x/@2x/@3x variants, manual Dark Mode handling, manual Dynamic Type scaling, and custom animation code. The 10 minutes to find the right SF Symbol saves hours of asset management."

Time cost of skipping: 2-4 hours managing assets + ongoing maintenance vs 10 minutes finding the right symbol.

Scenario 2: "We'll add animations later"

Setup: Sprint deadline. PM says animations are polish and can wait.

Why this matters: Retrofitting symbol effects requires restructuring state management. Effects triggered by value: changes need the right state architecture from the start.

Professional response: "Adding .symbolEffect(.bounce, value: count) takes one line. Retrofitting the state to support it later takes a refactor. Let me add the effect now — it's literally one modifier."

Scenario 3: "Draw animations look janky on our custom symbols"

Setup: Custom symbols have Draw animations that look wrong — paths draw in unexpected order or direction.

Why this matters: Draw annotation requires intentional guide point placement. Without it, the system guesses and often gets it wrong.

Fix: Open custom symbols in SF Symbols 7 app, add guide points explicitly to each path defining start/end/direction. Test each weight variant. See Custom Symbol Draw Annotation section above.

Resources

WWDC: 2023-10257, 2023-10258, 2024-10188, 2025-337

Docs: /symbols, /symbols/symboleffect, /symbols/symbolrenderingmode, /swiftui/image/symboleffect(*:options:value:), /swiftui/image/symbolrenderingmode(*:)

Skills: axiom-sf-symbols-ref, axiom-hig-ref, axiom-swiftui-animation-ref

Last Updated Based on WWDC 2023/10257-10258, WWDC 2024/10188, WWDC 2025/337 Version iOS 17+ (effects), iOS 18+ (Wiggle/Rotate/Breathe), iOS 26+ (Draw On/Off, Variable Draw, Gradients)