Scope dark mode change only to the presenting sheet (#6144)

* Scope dark mode change only to the presenting sheet, instead of the whole window

* Apply review suggestions to the presentation colour scheme modifier

API:
- Take a `ColorScheme?` at the SwiftUI level instead of a `UIUserInterfaceStyle`
  and map it once inside the representable (`nil` means no override).
- Rename to `presentationColorScheme` and the file to match.
- Restore the `preferredColorScheme` property on the media preview details and
  redact confirmation views, and the `nil` at the media timeline call site, so
  no UIKit types leak into the views.

Cleanup:
- Walk the responder chain with `sequence(first:next:)` instead of a while loop.

* Re-record the media upload preview iPad snapshots

The Cancel button no longer has an explicit tint, so its label colour changed
very slightly from `textActionPrimary` to the default. Only the iPad references
include the toolbar, which is why the iPhone ones were unaffected.

ElementX.xcodeproj/project.pbxproj

@@ -453,6 +453,7 @@
 		4949C8C12669D1B5E082366E /* QRCodeLoginScreen.swift in Sources */ = {isa = PBXBuildFile; fileRef = BFA9EA59D5C0DA1BFC7B3621 /* QRCodeLoginScreen.swift */; };
 		49500BBA1CD65A5AE252D970 /* RoomDirectorySearchScreenModels.swift in Sources */ = {isa = PBXBuildFile; fileRef = 41BB37D96C3EA18F3CE8675D /* RoomDirectorySearchScreenModels.swift */; };
 		49BBEC46D523BF6A41400048 /* URLTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 3AB34956C87731AB094DB33A /* URLTests.swift */; };
+		4A091BAF20F4D27DF66B7F0A /* PresentationColorSchemeModifier.swift in Sources */ = {isa = PBXBuildFile; fileRef = EDF6E8208542BE7A02A94939 /* PresentationColorSchemeModifier.swift */; };
 		4A361E8BAFFA20B9719B47F5 /* InviteUsersConfirmationSheetView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 8E97CF050B0168F3D605F0E9 /* InviteUsersConfirmationSheetView.swift */; };
 		4A4110369DBB79E4A314F415 /* ComposerToolbarViewModelProtocol.swift in Sources */ = {isa = PBXBuildFile; fileRef = B0618820D26F9871A4BBB40E /* ComposerToolbarViewModelProtocol.swift */; };
 		4A618590DEB72C4F186BFED4 /* UserSessionFlowCoordinator.swift in Sources */ = {isa = PBXBuildFile; fileRef = C99FDEEB71173C4C6FA2734C /* UserSessionFlowCoordinator.swift */; };
@@ -3150,6 +3151,7 @@
 		ED49073BB1C1FC649DAC2CCD /* LocationRoomTimelineView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = LocationRoomTimelineView.swift; sourceTree = "<group>"; };
 		ED60E4D2CD678E1EBF16F77A /* BlockedUsersScreen.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = BlockedUsersScreen.swift; sourceTree = "<group>"; };
 		EDDE826EAB1BAB80C1104980 /* SpaceFlowCoordinator.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SpaceFlowCoordinator.swift; sourceTree = "<group>"; };
+		EDF6E8208542BE7A02A94939 /* PresentationColorSchemeModifier.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = PresentationColorSchemeModifier.swift; sourceTree = "<group>"; };
 		EE378083653EF0C9B5E9D580 /* EmoteRoomTimelineItemContent.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = EmoteRoomTimelineItemContent.swift; sourceTree = "<group>"; };
 		EE61568A225F7AA068583AA7 /* SignallingTimelineItemProviderMock.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SignallingTimelineItemProviderMock.swift; sourceTree = "<group>"; };
 		EE8BCD14EFED23459A43FDFF /* ja */ = {isa = PBXFileReference; lastKnownFileType = text.plist.strings; name = ja; path = ja.lproj/Localizable.strings; sourceTree = "<group>"; };
@@ -3466,6 +3468,7 @@
 				2A38B60F40D47397CB3B3C9C /* CollapsedInPlaceModifier.swift */,
 				F03AEAA2F66E796C365EFD58 /* ElementNavigationStack.swift */,
 				55BA4D3DFEA16CDD3FE99064 /* InverseMask.swift */,
+				EDF6E8208542BE7A02A94939 /* PresentationColorSchemeModifier.swift */,
 				5DB56ABD78E60920ACE43087 /* PreviewScrollView.swift */,
 				D2C513A6CD99E6C3C163DA1E /* RowDivider.swift */,
 				693E16574C6F7F9FA1015A8C /* Search.swift */,
@@ -9121,6 +9124,7 @@
 				1307268DC41730E5BCF7D9A0 /* PollView.swift in Sources */,
 				DF504B10A4918F971A57BEF2 /* PostHogAnalyticsClient.swift in Sources */,
 				CF7D38F6478CDA5E48CA185D /* PresenceService.swift in Sources */,
+				4A091BAF20F4D27DF66B7F0A /* PresentationColorSchemeModifier.swift in Sources */,
 				BDCF42966007770A33D90E15 /* PreviewScrollView.swift in Sources */,
 				6793E75E3EBE48EBB8F857AF /* ProcessInfo.swift in Sources */,
 				69DE29C3E3180BB17D840690 /* ProgressCursorModifier.swift in Sources */,

ElementX/Sources/Other/SwiftUI/PresentationColorSchemeModifier.swift

@@ -0,0 +1,79 @@
+//
+// Copyright 2026 Element Creations Ltd.
+//
+// SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+// Please see LICENSE files in the repository root for full details.
+//
+
+import SwiftUI
+
+extension View {
+    /// Forces the colour scheme of the sheet or popover containing this view without touching the
+    /// rest of the app. Does nothing when the view isn't presented modally or the scheme is `nil`.
+    ///
+    /// Prefer this over `preferredColorScheme` for modals: SwiftUI applies that modifier to the whole
+    /// window and can leave it applied when the presentation is torn down abnormally (#6093).
+    func presentationColorScheme(_ colorScheme: ColorScheme?) -> some View {
+        background(PresentationColorSchemeView(colorScheme: colorScheme))
+    }
+}
+
+private struct PresentationColorSchemeView: UIViewRepresentable {
+    let colorScheme: ColorScheme?
+    
+    func makeUIView(context: Context) -> InterfaceStyleView {
+        InterfaceStyleView(style: UIUserInterfaceStyle(colorScheme))
+    }
+    
+    func updateUIView(_ uiView: InterfaceStyleView, context: Context) {
+        uiView.style = UIUserInterfaceStyle(colorScheme)
+    }
+    
+    class InterfaceStyleView: UIView {
+        var style: UIUserInterfaceStyle {
+            didSet { applyStyle() }
+        }
+        
+        init(style: UIUserInterfaceStyle) {
+            self.style = style
+            super.init(frame: .zero)
+            isUserInteractionEnabled = false
+        }
+        
+        @available(*, unavailable)
+        required init?(coder: NSCoder) {
+            fatalError("init(coder:) has not been implemented")
+        }
+        
+        override func didMoveToWindow() {
+            super.didMoveToWindow()
+            applyStyle()
+        }
+        
+        private func applyStyle() {
+            guard window != nil else { return }
+            targetViewController?.overrideUserInterfaceStyle = style
+        }
+        
+        /// The view controller that was actually presented, so the override covers its navigation bar too.
+        private var targetViewController: UIViewController? {
+            guard let next else { return nil }
+            return sequence(first: next) { $0.next }
+                .lazy
+                .compactMap { $0 as? UIViewController }
+                // Children of a presented controller also report a presentingViewController, so check the parent.
+                .first { $0.presentingViewController != nil && $0.parent == nil }
+        }
+    }
+}
+
+private extension UIUserInterfaceStyle {
+    init(_ colorScheme: ColorScheme?) {
+        self = switch colorScheme {
+        case .light: .light
+        case .dark: .dark
+        case .none: .unspecified
+        @unknown default: .unspecified
+        }
+    }
+}

ElementX/Sources/Screens/FilePreviewScreen/View/TimelineMediaPreviewDetailsView.swift

@@ -35,7 +35,7 @@ struct TimelineMediaPreviewDetailsView: View {
         .presentationDetents([.height(sheetHeight)])
         .presentationDragIndicator(.visible)
         .presentationBackground(.compound.bgCanvasDefault)
-        .preferredColorScheme(preferredColorScheme)
+        .presentationColorScheme(preferredColorScheme)
         .sheet(item: $context.redactConfirmationItem) { item in
             TimelineMediaPreviewRedactConfirmationView(item: item,
                                                        context: context,

ElementX/Sources/Screens/FilePreviewScreen/View/TimelineMediaPreviewRedactConfirmationView.swift

@@ -38,7 +38,7 @@ struct TimelineMediaPreviewRedactConfirmationView: View {
         .presentationDetents([.height(sheetHeight + topPadding)])
         .presentationDragIndicator(.visible)
         .presentationBackground(.compound.bgCanvasDefault)
-        .preferredColorScheme(preferredColorScheme)
+        .presentationColorScheme(preferredColorScheme)
     }
     
     private var header: some View {

ElementX/Sources/Screens/MediaUploadPreviewScreen/View/MediaUploadPreviewScreen.swift

@@ -16,8 +16,6 @@ import SwiftUI
 import UniformTypeIdentifiers
 
 struct MediaUploadPreviewScreen: View {
-    @Environment(\.colorScheme) private var colorScheme
-    
     @Bindable var context: MediaUploadPreviewScreenViewModel.Context
     
     @State private var captionWarningFrame: CGRect = .zero
@@ -28,8 +26,10 @@ struct MediaUploadPreviewScreen: View {
         ProcessInfo.processInfo.isiOSAppOnMac ? context.viewState.title ?? "" : ""
     }
     
-    private var colorSchemeOverride: ColorScheme {
+    /// Matches the dark chrome of the QLPreviewController. Scoped to the sheet rather than
-        ProcessInfo.processInfo.isiOSAppOnMac ? colorScheme : .dark
+    /// using `preferredColorScheme` which leaks into the whole app if the sheet fails to present.
+    private var colorSchemeOverride: ColorScheme? {
+        ProcessInfo.processInfo.isiOSAppOnMac ? nil : .dark
     }
     
     var body: some View {
@@ -49,7 +49,7 @@ struct MediaUploadPreviewScreen: View {
             .disabled(context.viewState.shouldDisableInteraction)
             .interactiveDismissDisabled()
             .presentationBackground(.background) // Fix a bug introduced by the caption warning.
-            .preferredColorScheme(colorSchemeOverride)
+            .presentationColorScheme(colorSchemeOverride)
             .onAppear(perform: focusComposerIfHardwareKeyboardConnected)
             .alert(item: $context.alertInfo)
             .sheet(isPresented: $context.isPresentingMediaEditor) {
@@ -60,6 +60,7 @@ struct MediaUploadPreviewScreen: View {
                     context.isPresentingMediaEditor = false
                 }
                 .ignoresSafeArea()
+                .presentationColorScheme(colorSchemeOverride)
                 // Make sure out of bound error alerts are shown even if the sheet is presented
                 .alert(item: $context.alertInfo)
             }
@@ -131,7 +132,7 @@ struct MediaUploadPreviewScreen: View {
                 .presentationDragIndicator(.visible)
                 .padding(.top, 19) // For the drag indicator
                 .presentationBackground(.compound.bgCanvasDefault)
-                .preferredColorScheme(colorSchemeOverride)
+                .presentationColorScheme(colorSchemeOverride)
         }
     }
     
@@ -165,9 +166,6 @@ struct MediaUploadPreviewScreen: View {
             Button { context.send(viewAction: .cancel) } label: {
                 Text(L10n.actionCancel)
             }
-            // Fix a bug with the preferredColorScheme on iOS 18 where the button doesn't
-            // follow the dark colour scheme on devices running with dark mode disabled.
-            .tint(.compound.textActionPrimary)
         }
         
         if isCurrentMediaImage {
@@ -175,9 +173,6 @@ struct MediaUploadPreviewScreen: View {
                 Button { context.isPresentingMediaEditor = true } label: {
                     CompoundIcon(\.crop)
                 }
-                // Fix a bug with the preferredColorScheme on iOS 18 where the button doesn't
-                // follow the dark colour scheme on devices running with dark mode disabled.
-                .tint(.compound.textActionPrimary)
             }
         }
     }

PreviewTests/Sources/__Snapshots__/PreviewTests/mediaUploadPreviewScreen.iPad-en-GB-0.png

@@ -1,3 +1,3 @@
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+oid sha256:f327e6dfe4c81dfaa2a654b89c973293e61bc16147595ab031eb6676f8313f3e
-size 86282
+size 86285

PreviewTests/Sources/__Snapshots__/PreviewTests/mediaUploadPreviewScreen.iPad-pseudo-0.png

@@ -1,3 +1,3 @@
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-oid sha256:fd75072b7457c5bbbaab3876368794273590c3e83ea0ea7cc9020f57c41fdf9a
+oid sha256:7397c1698bd8524eb1cdf99667fc1c0916b58d4fd59a752c15f6c71e89a30ae3
-size 87335
+size 87348