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.
AbeFroman
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