FB13705157

Sheet background flashes when changing detents

Basic Information

Which platform is most relevant for your report?

iOS

Which technology does your report involve?

SwiftUI

What type of feedback are you reporting?

Incorrect/Unexpected Behavior

What build does the issue occur on?

iOS 17.4 Seed 3 (21E5200d)

Where does the issue occur?

On device

Description

• Run the given code.
• Drag the sheet up and down.
• Notice that the background of the sheet flashes, when the background is partially transparent.
• I would expect the background of the sheet not to flash.
• Moving the SheetView into ContentView seems to reduce the chances of it happening, but doesn't solve the problem.
• Can use SwiftUIIntrospect as a workaround.

Evidence

Visual

Demo	Workaround

Code

AppleFeedback/FB13705157/demo.swift

Lines 1 to 30 in 5b5f40d

	import SwiftUI
	struct ContentView: View {
	@State private var presented = true
	var body: some View {
	Button("Present") {
	presented = true
	}
	.sheet(isPresented: $presented) {
	SheetView()
	}
	.frame(maxWidth: .infinity, maxHeight: .infinity)
	.background(Color.red)
	}
	}
	struct SheetView: View {
	@State private var detent: PresentationDetent = .medium
	var body: some View {
	Text("Sheet")
	.presentationBackground(.regularMaterial)
	.presentationDetents([.medium, .large], selection: $detent)
	}
	}
	#Preview {
	ContentView()
	}

AppleFeedback/FB13705157/workaround.swift

Lines 1 to 34 in 5b5f40d

	import SwiftUI
	import SwiftUIIntrospect
	struct ContentView: View {
	@State private var presented = true
	var body: some View {
	Button("Present") {
	presented = true
	}
	.sheet(isPresented: $presented) {
	SheetView()
	}
	.frame(maxWidth: .infinity, maxHeight: .infinity)
	.background(Color.red)
	}
	}
	struct SheetView: View {
	@State private var detent: PresentationDetent = .medium
	var body: some View {
	Text("Sheet")
	.presentationBackground(.regularMaterial)
	.presentationDetents([.medium, .large], selection: $detent)
	.introspect(.sheet, on: .iOS(.v17)) { sheet in
	sheet.presentedViewController.view.backgroundColor = .clear
	}
	}
	}
	#Preview {
	ContentView()
	}