ios: let native scrolling handle Agent keyboard resizing

2026-10-16 12:37:04 -07:00
parent d5427926d5
commit e681e9e05c
2 changed files with 140 additions and 116 deletions
@@ -18,20 +18,20 @@ struct SybilAgentView: View {
 }

 // Draft edits and keyboard focus belong to the composer. The transcript observes
-// only room/render/scroll state; resizing is handled by its scroll geometry.
+// only room/render/scroll state; SwiftUI handles keyboard avoidance.
 private struct AgentTranscriptView: View {
    var room: SybilAgentRoom
    var topInset: CGFloat
    var latestRequest: Int
    @Environment(\.accessibilityReduceMotion) private var reduceMotion
    @State private var atLatest = true
-    @State private var isScrolling = false
+    @State private var scrollPhase: ScrollPhase = .idle
    @State private var historyLimit = 100
    @State private var historyStartID: String?
    @State private var scrollPosition = ScrollPosition()
    @State private var scrollTracking = AgentScrollTracking()
    @State private var appeared = false
-    private let bottomID = "agent-bottom"
+    private var isScrolling: Bool { scrollPhase.isScrolling }

    private var visibleReadingAnchor: AgentReadingAnchor? {
        scrollTracking.rowFrames.filter { $0.value.maxY > topInset && $0.value.minY < scrollTracking.metrics.height }
@@ -48,129 +48,130 @@ private struct AgentTranscriptView: View {
        let allMessages = transcript.messages
        let startIndex = transcript.startIndex
        let displayed = transcript.displayed
-        ScrollViewReader { proxy in
-            ScrollView {
-                LazyVStack(alignment: .leading, spacing: 15) {
-                    if allMessages.count > displayed.count {
-                        Button("Load earlier messages") {
-                            // Loading older history may move the viewport as lazy
-                            // row estimates settle; do not chase the old position.
-                            scrollTracking.rowFrames = [:]
-                            atLatest = false
-                            historyLimit += 100
-                            historyStartID = allMessages[max(0, startIndex - 100)].id
-                        }
-                        .frame(maxWidth: .infinity)
-                        .padding(.vertical, 10)
+        ScrollView {
+            LazyVStack(alignment: .leading, spacing: 15) {
+                if allMessages.count > displayed.count {
+                    Button("Load earlier messages") {
+                        // Loading older history may move the viewport as lazy
+                        // row estimates settle; do not chase the old position.
+                        scrollTracking.rowFrames = [:]
+                        atLatest = false
+                        historyLimit += 100
+                        historyStartID = allMessages[max(0, startIndex - 100)].id
                    }
-                    if room.isLoading { ProgressView("Loading messages…").frame(maxWidth: .infinity) }
-                    ForEach(Array(displayed.enumerated()), id: \.element.id) { index, message in
-                        AgentTranscriptRow(message: message, room: room, tracksReadingAnchor: !atLatest,
-                            startsDay: index == 0 || !Calendar.current.isDate(message.createdAt, inSameDayAs: displayed[index - 1].createdAt))
-                            .equatable()
-                            .modifier(AgentEntrance(animate: appeared && rendered.entranceIDs.contains(message.id), reduceMotion: reduceMotion))
-                            .id(message.id)
-                    }
-                    if rendered.isTyping {
-                        HStack(spacing: 9) {
-                            AgentAvatar()
-                            ProgressView().controlSize(.small)
-                            Text("Sybil is thinking…").font(.sybil(.caption))
-                        }
-                        .foregroundStyle(SybilTheme.textMuted)
-                        .accessibilityIdentifier("agent-typing")
-                    }
-                    Color.clear.frame(height: 1).id(bottomID)
+                    .frame(maxWidth: .infinity)
+                    .padding(.vertical, 10)
                }
-                .scrollTargetLayout()
-                .padding(.horizontal, 16)
-                .padding(.bottom, 16)
-                // Match normal chat: content clears the header, while the
-                // viewport extends beneath the shared navigation fade.
-                .padding(.top, 16 + topInset)
-                .frame(maxWidth: SybilLayout.webContentMaxWidth)
-                .frame(maxWidth: .infinity)
-            }
-            .accessibilityIdentifier("agent-transcript")
-            .coordinateSpace(name: "agent-scroll")
-            .scrollPosition($scrollPosition)
-            .defaultScrollAnchor(.bottom, for: .initialOffset)
-            .defaultScrollAnchor(.bottom, for: .alignment)
-            .scrollDismissesKeyboard(.interactively)
-            .onScrollPhaseChange { _, phase in
-                isScrolling = phase.isScrolling
-            }
-            .onScrollGeometryChange(for: AgentScrollMetrics.self) { geometry in
-                AgentScrollMetrics(offset: geometry.contentOffset.y,
-                    height: geometry.containerSize.height,
-                    contentHeight: geometry.contentSize.height,
-                    bottomInset: geometry.contentInsets.bottom, topInset: geometry.contentInsets.top,
-                    visibleBottom: geometry.visibleRect.maxY)
-            } action: { previous, next in
-                #if DEBUG
-                AgentRenderDiagnostics.record("scrollGeometry")
-                #endif
-                scrollTracking.metrics = next
-                if scrollTracking.atBottom != next.atBottom { scrollTracking.atBottom = next.atBottom }
-                if isScrolling || next.contentHeight <= next.height { atLatest = next.atBottom }
-                if atLatest, !isScrolling,
-                   previous.height != next.height || previous.contentHeight != next.contentHeight || previous.bottomInset != next.bottomInset {
-                    proxy.scrollTo(bottomID, anchor: .bottom)
+                if room.isLoading { ProgressView("Loading messages…").frame(maxWidth: .infinity) }
+                ForEach(Array(displayed.enumerated()), id: \.element.id) { index, message in
+                    AgentTranscriptRow(message: message, room: room, tracksReadingAnchor: !atLatest,
+                        startsDay: index == 0 || !Calendar.current.isDate(message.createdAt, inSameDayAs: displayed[index - 1].createdAt))
+                        .equatable()
+                        .modifier(AgentEntrance(animate: appeared && rendered.entranceIDs.contains(message.id), reduceMotion: reduceMotion))
+                        .id(message.id)
                }
-            }
-            .onPreferenceChange(AgentRowFrames.self) { frames in
-                #if DEBUG
-                AgentRenderDiagnostics.record("rowPreferences")
-                #endif
-                let anchor = !atLatest && !isScrolling ? visibleReadingAnchor : nil
-                if let anchor, let frame = frames[anchor.id], abs(frame.minY - anchor.offset) > 1 {
-                    // Preserve ordinary reading position after new messages or
-                    // text reflow. Normalize the saved frames to
-                    // the requested offset so the next layout cannot undo it.
-                    let requested = scrollTracking.metrics.offset + frame.minY - anchor.offset
-                    let target = min(max(requested, -scrollTracking.metrics.topInset), scrollTracking.metrics.maximumOffset)
-                    let appliedShift = target - scrollTracking.metrics.offset
-                    scrollTracking.rowFrames = frames.mapValues { $0.offsetBy(dx: 0, dy: -appliedShift) }
-                    if abs(appliedShift) > 1 {
-                        // Geometry reports the raw offset; ScrollPosition uses
-                        // zero at the top inset, including the safe area.
-                        scrollPosition.scrollTo(y: target + scrollTracking.metrics.topInset)
+                if rendered.isTyping {
+                    HStack(spacing: 9) {
+                        AgentAvatar()
+                        ProgressView().controlSize(.small)
+                        Text("Sybil is thinking…").font(.sybil(.caption))
                    }
-                } else {
-                    scrollTracking.rowFrames = frames
+                    .foregroundStyle(SybilTheme.textMuted)
+                    .accessibilityIdentifier("agent-typing")
                }
+                Color.clear.frame(height: 1)
            }
-            .overlay(alignment: .bottomTrailing) {
-                if !atLatest {
-                    Button {
-                        atLatest = true
-                        withAnimation(reduceMotion ? nil : .easeOut(duration: 0.24)) { proxy.scrollTo(bottomID, anchor: .bottom) }
-                    } label: {
-                        Label(room.unreadCount > 0 ? "\(room.unreadCount) unread" : "Latest", systemImage: "arrow.down")
-                            .font(.sybil(.caption, weight: .semibold))
-                            .padding(12)
-                            .background(SybilTheme.surfaceStrong, in: Capsule())
-                            .overlay(Capsule().stroke(SybilTheme.border))
-                    }
-                    .padding(14)
-                    .accessibilityIdentifier("agent-jump-latest")
+            .scrollTargetLayout()
+            .padding(.horizontal, 16)
+            .padding(.bottom, 16)
+            // Match normal chat: content clears the header, while the
+            // viewport extends beneath the shared navigation fade.
+            .padding(.top, 16 + topInset)
+            .frame(maxWidth: SybilLayout.webContentMaxWidth)
+            .frame(maxWidth: .infinity)
+        }
+        .accessibilityIdentifier("agent-transcript")
+        .coordinateSpace(name: "agent-scroll")
+        .scrollPosition($scrollPosition)
+        .defaultScrollAnchor(.bottom, for: .initialOffset)
+        // Let SwiftUI follow size changes, including keyboard avoidance,
+        // without competing scrollTo calls from geometry updates.
+        .defaultScrollAnchor(atLatest ? .bottom : nil, for: .sizeChanges)
+        .defaultScrollAnchor(.bottom, for: .alignment)
+        .scrollDismissesKeyboard(.interactively)
+        .onScrollPhaseChange { _, phase in
+            scrollPhase = phase
+        }
+        .onScrollGeometryChange(for: AgentScrollMetrics.self) { geometry in
+            AgentScrollMetrics(offset: geometry.contentOffset.y,
+                height: geometry.containerSize.height,
+                contentHeight: geometry.contentSize.height,
+                bottomInset: geometry.contentInsets.bottom, topInset: geometry.contentInsets.top,
+                visibleBottom: geometry.visibleRect.maxY)
+        } action: { _, next in
+            #if DEBUG
+            AgentRenderDiagnostics.record("scrollGeometry")
+            #endif
+            scrollTracking.metrics = next
+            if scrollTracking.atBottom != next.atBottom { scrollTracking.atBottom = next.atBottom }
+            // Only user scrolling changes follow intent. Animated Latest
+            // navigation and native keyboard resizing must not cancel it.
+            if (isScrolling && scrollPhase != .animating) || next.contentHeight <= next.height {
+                atLatest = next.atBottom
+            }
+        }
+        .onPreferenceChange(AgentRowFrames.self) { frames in
+            #if DEBUG
+            AgentRenderDiagnostics.record("rowPreferences")
+            #endif
+            let anchor = !atLatest && !isScrolling ? visibleReadingAnchor : nil
+            if let anchor, let frame = frames[anchor.id], abs(frame.minY - anchor.offset) > 1 {
+                // Preserve ordinary reading position after new messages or
+                // text reflow. Normalize the saved frames to
+                // the requested offset so the next layout cannot undo it.
+                let requested = scrollTracking.metrics.offset + frame.minY - anchor.offset
+                let target = min(max(requested, -scrollTracking.metrics.topInset), scrollTracking.metrics.maximumOffset)
+                let appliedShift = target - scrollTracking.metrics.offset
+                scrollTracking.rowFrames = frames.mapValues { $0.offsetBy(dx: 0, dy: -appliedShift) }
+                if abs(appliedShift) > 1 {
+                    // Geometry reports the raw offset; ScrollPosition uses
+                    // zero at the top inset, including the safe area.
+                    scrollPosition.scrollTo(y: target + scrollTracking.metrics.topInset)
                }
+            } else {
+                scrollTracking.rowFrames = frames
            }
-            .onAppear {
-                appeared = true
-                if !room.isLoading { historyStartID = displayed.first?.id }
-            }
-            .onChange(of: room.isLoading) { _, loading in
-                if !loading && historyStartID == nil { historyStartID = displayed.first?.id }
-            }
-            .onChange(of: allMessages.count) { _, _ in
-                if atLatest { proxy.scrollTo(bottomID, anchor: .bottom) }
-            }
-            .onChange(of: latestRequest) { _, _ in
-                atLatest = true
-                proxy.scrollTo(bottomID, anchor: .bottom)
+        }
+        .overlay(alignment: .bottomTrailing) {
+            if !atLatest {
+                Button {
+                    atLatest = true
+                    withAnimation(reduceMotion ? nil : .easeOut(duration: 0.24)) { scrollPosition.scrollTo(edge: .bottom) }
+                } label: {
+                    Label(room.unreadCount > 0 ? "\(room.unreadCount) unread" : "Latest", systemImage: "arrow.down")
+                        .font(.sybil(.caption, weight: .semibold))
+                        .padding(12)
+                        .background(SybilTheme.surfaceStrong, in: Capsule())
+                        .overlay(Capsule().stroke(SybilTheme.border))
+                }
+                .padding(14)
+                .accessibilityIdentifier("agent-jump-latest")
            }
        }
+        .onAppear {
+            appeared = true
+            if !room.isLoading { historyStartID = displayed.first?.id }
+        }
+        .onChange(of: room.isLoading) { _, loading in
+            if !loading && historyStartID == nil { historyStartID = displayed.first?.id }
+        }
+        .onChange(of: allMessages.count) { _, _ in
+            if atLatest { scrollPosition.scrollTo(edge: .bottom) }
+        }
+        .onChange(of: latestRequest) { _, _ in
+            atLatest = true
+            scrollPosition.scrollTo(edge: .bottom)
+        }
        .modifier(AgentReadAcknowledgement(room: room, tracking: scrollTracking,
                                          atLatest: atLatest, isScrolling: isScrolling))
    }