107 lines
3.6 KiB
Swift
107 lines
3.6 KiB
Swift
//
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// Copyright 2018 Signal Messenger, LLC
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// SPDX-License-Identifier: AGPL-3.0-only
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//
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import SignalServiceKit
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public class GradientView: UIView {
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public override class var layerClass: AnyClass { CAGradientLayer.self }
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public var gradientLayer: CAGradientLayer { layer as! CAGradientLayer }
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public var colors: [UIColor] {
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didSet {
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updateGradientColors()
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}
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}
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public var locations: [CGFloat]? {
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didSet {
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updateGradientLocations()
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}
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}
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public convenience init(from fromColor: UIColor, to toColor: UIColor) {
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self.init(colors: [ fromColor, toColor ])
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}
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public init(colors: [UIColor], locations: [CGFloat]? = nil) {
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self.colors = colors
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self.locations = locations
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super.init(frame: .zero)
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updateGradientColors()
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updateGradientLocations()
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}
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public required init?(coder aDecoder: NSCoder) {
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fatalError("init(coder:) has not been implemented")
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}
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private func updateGradientColors() {
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guard gradientWithinPerformanceLimits() else { return }
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gradientLayer.colors = colors.map { $0.cgColor }
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}
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private func updateGradientLocations() {
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guard gradientWithinPerformanceLimits() else { return }
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if let locations = locations, !locations.isEmpty {
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gradientLayer.locations = locations.map { NSNumber(value: $0) }
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} else {
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gradientLayer.locations = nil
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}
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}
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private func gradientWithinPerformanceLimits() -> Bool {
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if (colors.count * 4 + (locations?.count ?? 0)) > 512 {
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owsFailDebug("Too many gradient points")
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return false
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}
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return true
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}
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/// Sets the `startPoint` and `endPoint` of the layer to reflect an angle in degrees
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/// where 0° starts at 12 o'clock and proceeds in a clockwise direction.
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public func setAngle(_ angle: UInt32) {
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// While design provides gradients with 0° at 12 o'clock, core animation's
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// coordinate system works with 0° at 3 o'clock moving in a counter clockwise
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// direction. We need to convert the provided angle accordingly before
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// calculating the gradient's start and end points.
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let caAngle =
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(360 - angle) // Invert to counter clockwise direction
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+ 90 // Rotate 90° counter clockwise to shift the start from 3 o'clock to 12 o'clock
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let radians = CGFloat(caAngle) * .pi / 180.0
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// (x,y) in terms of the signed unit circle
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var endPoint = CGPoint(x: cos(radians), y: sin(radians))
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// extrapolate to signed unit square
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if abs(endPoint.x) > abs(endPoint.y) {
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endPoint.x = endPoint.x > 0 ? 1 : -1
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endPoint.y = endPoint.x * tan(radians)
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} else {
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endPoint.y = endPoint.y > 0 ? 1 : -1
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endPoint.x = endPoint.y / tan(radians)
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}
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// The signed unit square is a coordinate space from:
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// (-1,-1) to (1,1), but the gradient coordinate space
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// ranges from (0,0) to (1,1) with 0 being the top
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// left. Convert each point accordingly to calculate
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// the final points.
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func convertPointToGradientSpace(_ point: CGPoint) -> CGPoint {
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return CGPoint(
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x: (point.x + 1) * 0.5,
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y: 1.0 - (point.y + 1) * 0.5
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)
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}
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// The start point will always be at the opposite side of the signed unit square.
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gradientLayer.startPoint = convertPointToGradientSpace(CGPoint(x: -endPoint.x, y: -endPoint.y))
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gradientLayer.endPoint = convertPointToGradientSpace(endPoint)
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}
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}
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