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chore: improve performance of indeterminate spinner #184

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Jun 16, 2025
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chore: improve performance of indeterminate spinner #184

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92 changes: 67 additions & 25 deletions Coder-Desktop/Coder-Desktop/Views/CircularProgressView.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -8,45 +8,35 @@ struct CircularProgressView: View {
var primaryColor: Color = .secondary
var backgroundColor: Color = .secondary.opacity(0.3)

@State private var rotation = 0.0
@State private var trimAmount: CGFloat = 0.15

var autoCompleteThreshold: Float?
var autoCompleteDuration: TimeInterval?

var body: some View {
ZStack {
// Background circle
Circle()
.stroke(backgroundColor, style: StrokeStyle(lineWidth: strokeWidth, lineCap: .round))
.frame(width: diameter, height: diameter)
Group {
if let value {
// Determinate gauge
if let value {
ZStack {
Circle()
.stroke(backgroundColor, style: StrokeStyle(lineWidth: strokeWidth, lineCap: .round))

Circle()
.trim(from: 0, to: CGFloat(displayValue(for: value)))
.stroke(primaryColor, style: StrokeStyle(lineWidth: strokeWidth, lineCap: .round))
.frame(width: diameter, height: diameter)
.rotationEffect(.degrees(-90))
.animation(autoCompleteAnimation(for: value), value: value)
} else {
// Indeterminate gauge
Circle()
.trim(from: 0, to: trimAmount)
.stroke(primaryColor, style: StrokeStyle(lineWidth: strokeWidth, lineCap: .round))
.frame(width: diameter, height: diameter)
.rotationEffect(.degrees(rotation))
}
.frame(width: diameter, height: diameter)

} else {
IndeterminateSpinnerView(
diameter: diameter,
strokeWidth: strokeWidth,
primaryColor: NSColor(primaryColor),
backgroundColor: NSColor(backgroundColor)
)
.frame(width: diameter, height: diameter)
}
}
.frame(width: diameter + strokeWidth * 2, height: diameter + strokeWidth * 2)
.onAppear {
if value == nil {
withAnimation(.linear(duration: 0.8).repeatForever(autoreverses: false)) {
rotation = 360
}
}
}
}

private func displayValue(for value: Float) -> Float {
Expand Down Expand Up @@ -78,3 +68,55 @@ extension CircularProgressView {
return view
}
}

// We note a constant >10% CPU usage when using a SwiftUI rotation animation that
// repeats forever, while this implementation, using Core Animation, uses <1% CPU.
struct IndeterminateSpinnerView: NSViewRepresentable {
var diameter: CGFloat
var strokeWidth: CGFloat
var primaryColor: NSColor
var backgroundColor: NSColor

func makeNSView(context _: Context) -> NSView {
let view = NSView(frame: NSRect(x: 0, y: 0, width: diameter, height: diameter))
view.wantsLayer = true

guard let viewLayer = view.layer else { return view }

let fullPath = NSBezierPath(
ovalIn: NSRect(x: 0, y: 0, width: diameter, height: diameter)
).cgPath

let backgroundLayer = CAShapeLayer()
backgroundLayer.path = fullPath
backgroundLayer.strokeColor = backgroundColor.cgColor
backgroundLayer.fillColor = NSColor.clear.cgColor
backgroundLayer.lineWidth = strokeWidth
viewLayer.addSublayer(backgroundLayer)

let foregroundLayer = CAShapeLayer()

foregroundLayer.frame = viewLayer.bounds
foregroundLayer.path = fullPath
foregroundLayer.strokeColor = primaryColor.cgColor
foregroundLayer.fillColor = NSColor.clear.cgColor
foregroundLayer.lineWidth = strokeWidth
foregroundLayer.lineCap = .round
foregroundLayer.strokeStart = 0
foregroundLayer.strokeEnd = 0.15
viewLayer.addSublayer(foregroundLayer)

let rotationAnimation = CABasicAnimation(keyPath: "transform.rotation")
rotationAnimation.fromValue = 0
rotationAnimation.toValue = 2 * Double.pi
rotationAnimation.duration = 1.0
rotationAnimation.repeatCount = .infinity
rotationAnimation.isRemovedOnCompletion = false

foregroundLayer.add(rotationAnimation, forKey: "rotationAnimation")

return view
}

func updateNSView(_: NSView, context _: Context) {}
}
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