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DrawingGroup on Bezier Curve Causing Crash (Xcode 12.1 / iOS 14.1)
Hi All, I updated to Xcode 12.1 today and encountered some unexpected behavior with Metal & curved paths in my app. It took me a few hours to track down the source of this issue, so wanted to share in case anyone else has encountered this problem or has suggestions. Problem Applying .drawingGroup() to a View containing a bezier curve (e.g., path.addCurve() or path.addQuadCurve()) causes the app to crash immediately, with only cryptic output in the console. Notes: doesn't happen when drawing straight lines (path.addLine()), only curves appears to be limited to the Simulators, as the crash doesn't occur on my iPhone XR / iOS 14.1 removing .drawingGroup() stops app from crashing problem did not occur when using Xcode 12.0 Example Code import SwiftUI @main struct TestApp: App {   var body: some Scene {     WindowGroup {       TestView()     }   } } struct TestView: View {       @State private var redFill: Bool = true       var body: some View {           TestPath()     .fill(redFill ? Color.red : Color.blue)     // Drawing group here causes app to crash     .drawingGroup()           Button(action: {       redFill.toggle()     }) {       Text("Change Color")     }         } } struct TestPath: Shape {       func path(in rect: CGRect) -> Path {     let width: CGFloat = rect.size.width     let height: CGFloat = rect.size.height           let pathWidth: CGFloat = 200           let startPoint = CGPoint(       x: 0.5*(width - pathWidth),       y: 0.5*(height)     )     let endPoint = CGPoint(       x: 0.5*(width + pathWidth),       y: 0.5*(height)     )           let control1 = CGPoint(       x: 0.5*(width),       y: 0.5*(height + pathWidth)     )     let control2 = CGPoint(       x: 0.5*(width),       y: 0.5*(height - pathWidth)     )           let path = Path { path in       path.move(to: startPoint)       path.addCurve(         to: endPoint,         control1: control1,         control2: control2       )       path.closeSubpath()     }           return path         } } Console Output ... Metal GPU Frame Capture Enabled ... Metal API Validation Enabled ... [] nw_protocol_get_quic_image_block_invoke dlopen libquic failed ... Connection 1: received failure notification ... Connection 1: failed to connect 3:-9816, reason -1 ... Connection 1: encountered error(3:-9816) ... Task <...>.<1> HTTP load failed, 0/0 bytes (error code: -1200 [3:-9816]) ... [error] precondition failure: pipeline error: accumulator_color-13f4500040004f: Compiler encountered an internal error ... CoreSimulator 732.17 - Device: iPhone 11 (...) - Runtime: iOS 14.1 (18A8394) - DeviceType: iPhone 11 ... RenderBox precondition failure: pipeline error: accumulator_color-13f4500040004f: Compiler encountered an internal error.
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Oct ’20