Hug the content in every iOS content-fit sheet

ios/CashuWallet/Views/Components/LiquidGlassModifiers.swift

@@ -83,6 +83,59 @@
         modifier(ScreenEntryFade())
     }
 
+    /// Measures a content-fit sheet's body for
+    /// ``contentFitDetent(_:enabled:estimate:navigationBar:)``. Apply to the body
+    /// itself — inside the `NavigationStack`, for the sheets that host one.
+    ///
+    /// The `ScrollView` is load-bearing, not decoration. A detent derived from a
+    /// measurement taken inside that same sheet is a feedback loop — measured
+    /// height → detent → sheet height → the height proposed back to the content.
+    /// Since the chrome allowance is close to the real chrome, the loop is
+    /// *neutrally stable*: it settles wherever the first layout pass left it,
+    /// which during the presentation transition is roughly full-screen, and then
+    /// never recovers. A `ScrollView` proposes `nil` height to its content, so
+    /// the measured view always reports its **ideal** size no matter how tall the
+    /// sheet currently is — which breaks the loop.
+    ///
+    /// Never hang `.onGeometryChange` off a bare view to drive a detent.
+    func contentFitMeasured(_ onHeight: @escaping (CGFloat) -> Void) -> some View {
+        ScrollView {
+            self.onGeometryChange(for: CGFloat.self) { proxy in
+                proxy.size.height
+            } action: { newHeight in
+                onHeight(newHeight)
+            }
+        }
+        .scrollBounceBehavior(.basedOnSize)
+    }
+
+    /// Sizes a sheet to the height reported by ``contentFitMeasured(_:)``.
+    /// Apply on the sheet root, *outside* any `NavigationStack` — detents can't
+    /// be set from within the navigation content, which is why this is a pair.
+    ///
+    /// - Parameters:
+    ///   - contentHeight: the measured body height; `0` until geometry lands.
+    ///   - enabled: `false` falls through to `.large`, for steps that need the
+    ///     full sheet (Send's keypad/confirm, mint discovery's scrolling list).
+    ///   - estimate: first-frame stand-in before the measurement arrives, so the
+    ///     sheet doesn't open tiny and then jump.
+    ///   - navigationBar: whether the sheet hosts a `NavigationStack` with an
+    ///     inline title. Pass `false` for a bare sheet, or its detent carries
+    ///     44pt of chrome for a navigation bar that isn't there.
+    func contentFitDetent(
+        _ contentHeight: CGFloat,
+        enabled: Bool = true,
+        estimate: CGFloat = ContentFitSheetMetrics.bodyEstimate,
+        navigationBar: Bool = true
+    ) -> some View {
+        modifier(ContentFitDetent(
+            contentHeight: contentHeight,
+            enabled: enabled,
+            estimate: estimate,
+            navigationBar: navigationBar
+        ))
+    }
+
 }
 
 // MARK: - Sheet Close Button
@@ -161,7 +214,7 @@
     func body(content: Content) -> some View {
         content.presentationBackground {
             Color(uiColor: UIColor.systemBackground.resolvedColor(
                 with: UITraitCollection(traitsFrom: [
                     UITraitCollection(userInterfaceStyle: colorScheme == .dark ? .dark : .light),
                     UITraitCollection(userInterfaceLevel: .base),
                 ])
@@ -171,6 +224,102 @@
     }
 }
 
+// MARK: - Content-Fit Sheet Detent
+
+/// Pins the sheet to the newest computed height.
+///
+/// Handing `presentationDetents` a fresh single-element set is not enough. The
+/// body's height can be reported more than once as layout settles — a transient
+/// value, then the real one, milliseconds apart. UIKit resolves the new set but
+/// keeps the sheet on whichever detent it had already selected, so a transient
+/// measurement wins and the final one is silently ignored. Measured on an
+/// iPhone 17 Pro: 0 → 469 → 241pt in 70ms, leaving the sheet stuck at the 547pt
+/// detent instead of settling on 319pt.
+///
+/// Binding the selection alongside the set removes the race — the sheet is told
+/// which detent to be on, not merely which are available.
+private struct ContentFitDetent: ViewModifier {
+    let contentHeight: CGFloat
+    let enabled: Bool
+    let estimate: CGFloat
+    let navigationBar: Bool
+
+    @State private var selection: PresentationDetent = .large
+
+    private var detent: PresentationDetent {
+        guard enabled else { return .large }
+        return .height(ContentFitSheetMetrics.detentHeight(
+            for: contentHeight,
+            estimate: estimate,
+            hasNavigationBar: navigationBar
+        ))
+    }
+
+    func body(content: Content) -> some View {
+        content
+            .presentationDetents([detent], selection: $selection)
+            .onAppear { selection = detent }
+            .onChange(of: detent) { _, newDetent in selection = newDetent }
+    }
+}
+
+// MARK: - Content-Fit Sheet Metrics
+
+/// The one place the content-fit sheet arithmetic lives. Every partial-height
+/// sheet in the app — Send's compact input, Receive, Add Mint, connect-a-mint,
+/// onboarding's "What is ecash?" — hugs its content through
+/// ``View/contentFitMeasured(_:)`` +
+/// ``View/contentFitDetent(_:enabled:estimate:navigationBar:)``.
+@MainActor
+enum ContentFitSheetMetrics {
+    /// Inline navigation bar — the only chrome that actually consumes layout
+    /// height above the body.
+    ///
+    /// Notably absent: the drag indicator. `presentationDragIndicator` draws the
+    /// grabber as an *overlay* over the content's own top padding, so reserving
+    /// height for it doesn't move the content down — it just lands as dead space
+    /// at the bottom of the sheet. Same for any "breathing room" fudge: each
+    /// sheet's body already carries its own bottom padding, and the home
+    /// indicator gets the safe-area inset below that.
+    static let navigationBar: CGFloat = 44
+
+    /// Chrome above the measured body. The bottom safe area is *not* folded in
+    /// here — it's 34pt on Face ID devices and 0 on home-button ones, so it's
+    /// resolved per device in ``detentHeight(for:estimate:hasNavigationBar:)``.
+    static func chrome(hasNavigationBar: Bool) -> CGFloat {
+        hasNavigationBar ? navigationBar : 0
+    }
+
+    /// First-frame stand-in before the geometry measurement lands.
+    static let bodyEstimate: CGFloat = 220
+
+    /// Ceiling as a fraction of the screen. Past this the body scrolls inside
+    /// the sheet rather than the sheet growing — at accessibility text sizes an
+    /// unclamped detent would silently pin the sheet to full height.
+    static let maxScreenFraction: CGFloat = 0.9
+
+    static func detentHeight(
+        for contentHeight: CGFloat,
+        estimate: CGFloat = bodyEstimate,
+        hasNavigationBar: Bool = true
+    ) -> CGFloat {
+        let body = contentHeight > 0 ? contentHeight : estimate
+        let window = activeWindow
+        let wanted = body + chrome(hasNavigationBar: hasNavigationBar) + (window?.safeAreaInsets.bottom ?? 0)
+        // Read the ceiling from the *screen*, never from the sheet's own
+        // geometry — the latter would reintroduce the feedback loop this whole
+        // mechanism exists to avoid.
+        guard let screenHeight = window?.screen.bounds.height, screenHeight > 0 else { return wanted }
+        return min(wanted, screenHeight * maxScreenFraction)
+    }
+
+    private static var activeWindow: UIWindow? {
+        let scenes = UIApplication.shared.connectedScenes.compactMap { $0 as? UIWindowScene }
+        let scene = scenes.first { $0.activationState == .foregroundActive } ?? scenes.first
+        return scene?.keyWindow ?? scene?.windows.first
+    }
+}
+
 // MARK: - Canvas Divider
 
 /// Hairline divider used between rows on the single-canvas screens

ios/CashuWallet/Views/Main/OnboardingView.swift

@@ -38,9 +38,8 @@ struct OnboardingView: View {
     // First-mint state (create path)
     @State private var showConceptSheet = false
     /// Measured height of `conceptSheet`, so the sheet hugs its content instead
-    /// of sitting at a fixed `.medium` detent. Seeded with a plausible value so
-    /// the first layout pass is close; corrected on measure.
-    @State private var conceptSheetHeight: CGFloat = 360
+    /// of sitting at a fixed `.medium` detent.
+    @State private var conceptSheetHeight: CGFloat = 0
     @State private var selectedMintUrls: Set<String> = []
     @State private var customMintUrls: [String] = []
     @State private var showCustomMintInput = false
@@ -311,14 +310,11 @@ struct OnboardingView: View {
         // (~107pt on iPhone 17e, ~134pt on iPhone 11) rather than a designed
         // value. Measuring keeps the copy-to-button gap a constant 20pt and
         // matches Android, whose sheet already hugs its content.
-        .onGeometryChange(for: CGFloat.self) { proxy in
-            proxy.size.height
-        } action: { height in
-            conceptSheetHeight = height
-        }
-        // `.large` stays available so very large accessibility text can still
-        // expand past the measured height rather than clip.
-        .presentationDetents([.height(conceptSheetHeight), .large])
+        .contentFitMeasured { conceptSheetHeight = $0 }
+        // No `NavigationStack` here, so the detent must not reserve nav-bar
+        // chrome. Very large accessibility text scrolls inside the clamped
+        // sheet — the same contract as every other content-fit sheet.
+        .contentFitDetent(conceptSheetHeight, estimate: 360, navigationBar: false)
         .presentationDragIndicator(.visible)
     }
 

ios/CashuWallet/Views/Mints/AddMintSheet.swift

@@ -99,11 +99,7 @@ struct AddMintFormView: View {
         .padding(.horizontal, 20)
         .padding(.top, 8)
         .padding(.bottom, 16)
-        .onGeometryChange(for: CGFloat.self) { proxy in
-            proxy.size.height
-        } action: { newHeight in
-            onHeightChange(newHeight)
-        }
+        .contentFitMeasured { onHeightChange($0) }
         .navigationTitle("Add Mint")
         .navigationBarTitleDisplayMode(.inline)
         // Sheet, not fullScreenCover — the one presentation kind every
@@ -195,10 +191,7 @@ struct AddMintFormView: View {
 struct AddMintSheet: View {
     @Environment(\.dismiss) private var dismiss
 
-    @State private var contentHeight: CGFloat = 260
-
-    /// Matches the connect-a-mint sheet's chrome allowance.
-    private let sheetChrome: CGFloat = 108
+    @State private var contentHeight: CGFloat = 0
 
     var body: some View {
         NavigationStack {
@@ -208,7 +201,7 @@ struct AddMintSheet: View {
             )
         }
         // Hugs the form, like every other content-fit sheet in the app.
-        .presentationDetents([.height(contentHeight + sheetChrome)])
+        .contentFitDetent(contentHeight, estimate: 260)
         .presentationDragIndicator(.visible)
     }
 }

ios/CashuWallet/Views/Mints/ConnectMintView.swift

@@ -66,60 +66,53 @@ struct ConnectMintPicker: View {
     var onHeightChange: (CGFloat) -> Void = { _ in }
 
     var body: some View {
-        ScrollView {
-            VStack(alignment: .leading, spacing: 0) {
-                if context.showsHeadline {
-                    Text(ConnectMintContext.headline)
-                        .font(.title3.weight(.medium))
-                        .padding(.bottom, ConnectMintMetrics.headlineToSubtitle)
-                }
+        VStack(alignment: .leading, spacing: 0) {
+            if context.showsHeadline {
+                Text(ConnectMintContext.headline)
+                    .font(.title3.weight(.medium))
+                    .padding(.bottom, ConnectMintMetrics.headlineToSubtitle)
+            }
 
-                Text(ConnectMintContext.subtitle)
-                    .font(.subheadline)
-                    .foregroundStyle(.secondary)
-                    .fixedSize(horizontal: false, vertical: true)
+            Text(ConnectMintContext.subtitle)
+                .font(.subheadline)
+                .foregroundStyle(.secondary)
+                .fixedSize(horizontal: false, vertical: true)
 
-                SuggestedMintsSection(existingURLs: existingURLs, onAdd: onAdd)
+            SuggestedMintsSection(existingURLs: existingURLs, onAdd: onAdd)
 
-                if let errorMessage {
-                    InlineNotice(message: errorMessage, severity: .error)
-                        .padding(.top, ConnectMintMetrics.footerSpacing)
-                }
+            if let errorMessage {
+                InlineNotice(message: errorMessage, severity: .error)
+                    .padding(.top, ConnectMintMetrics.footerSpacing)
+            }
 
-                // Spacing lives in each label's vertical padding so the links keep
-                // 44pt hit targets; stacking them with plain spacing would leave
-                // ~20pt-tall taps.
-                VStack(spacing: 0) {
+            // Spacing lives in each label's vertical padding so the links keep
+            // 44pt hit targets; stacking them with plain spacing would leave
+            // ~20pt-tall taps.
+            VStack(spacing: 0) {
+                footerLink(
+                    title: "Add custom mint URL",
+                    systemImage: "plus",
+                    route: .addCustom
+                )
+                // Discovery rides Nostr relays over WebSockets. With the
+                // setting off it can only show a "turn this on" dead end, so
+                // it isn't offered at all.
+                if discoveryAvailable {
                     footerLink(
-                        title: "Add custom mint URL",
-                        systemImage: "plus",
-                        route: .addCustom
+                        title: "Discover mints",
+                        systemImage: "magnifyingglass",
+                        route: .discover
                     )
-                    // Discovery rides Nostr relays over WebSockets. With the
-                    // setting off it can only show a "turn this on" dead end, so
-                    // it isn't offered at all.
-                    if discoveryAvailable {
-                        footerLink(
-                            title: "Discover mints",
-                            systemImage: "magnifyingglass",
-                            route: .discover
-                        )
-                    }
                 }
-                // The first link carries 12pt of its own padding; net gap is the
-                // designed 20pt.
-                .padding(.top, ConnectMintMetrics.rowsToFooter - ConnectMintMetrics.footerSpacing)
-            }
-            .padding(.horizontal, ConnectMintMetrics.gutter)
-            .padding(.top, 8)
-            .padding(.bottom, 16)
-            .onGeometryChange(for: CGFloat.self) { proxy in
-                proxy.size.height
-            } action: { newHeight in
-                onHeightChange(newHeight)
             }
+            // The first link carries 12pt of its own padding; net gap is the
+            // designed 20pt.
+            .padding(.top, ConnectMintMetrics.rowsToFooter - ConnectMintMetrics.footerSpacing)
         }
-        .scrollBounceBehavior(.basedOnSize)
+        .padding(.horizontal, ConnectMintMetrics.gutter)
+        .padding(.top, 8)
+        .padding(.bottom, 16)
+        .contentFitMeasured { onHeightChange($0) }
     }
 
     @ViewBuilder
@@ -261,12 +254,9 @@ struct ConnectMintSheet: View {
     @ObservedObject private var settings = SettingsManager.shared
 
     @State private var route: ConnectMintRoute?
-    @State private var contentHeight: CGFloat = 220
+    @State private var contentHeight: CGFloat = 0
     @State private var addMintError: String?
 
-    /// Matches the Send sheet's compact-detent chrome allowance.
-    private let sheetChrome: CGFloat = 108
-
     var body: some View {
         NavigationStack {
             ConnectMintPicker(
@@ -296,9 +286,7 @@ struct ConnectMintSheet: View {
         // Both the shortlist and the pushed URL step hug their content, matching
         // Android. Only discovery fills the sheet — it hosts a scrolling list and
         // needs bounded height.
-        .presentationDetents(
-            route == .discover ? [.large] : [.height(contentHeight + sheetChrome)]
-        )
+        .contentFitDetent(contentHeight, enabled: route != .discover)
         .presentationDragIndicator(.visible)
         // Hugging the shortlist, this floats over the canvas and keeps the
         // system's elevated background; only the pushed full-height steps adopt