perf(macos): 消除拖动分隔条导致的全局渲染卡顿

macos/Sources/Lithe/Models/AppModel/AppModel+FeatureState.swift

@@ -218,6 +218,9 @@ extension AppModel {
     var gitReferences: [GitReference] { gitFeatureIfActive?.gitReferences ?? [] }
     var recentGitReferences: [GitReference] { gitFeatureIfActive?.recentGitReferences ?? [] }
     var gitCommits: [GitCommit] { gitFeatureIfActive?.gitCommits ?? [] }
+    /// Cheap stand-in for `gitCommits` as a change key. Comparing the array
+    /// itself made every `.task(id:)` evaluation walk the whole commit list.
+    var gitCommitsVersion: Int { gitFeatureIfActive?.gitCommitsVersion ?? 0 }
     var gitLogMatchedCommitHashes: Set<String>? {
         gitFeatureIfActive?.gitLogMatchedCommitHashes
     }

macos/Sources/Lithe/Services/Monitoring/LitheSignpost.swift

@@ -0,0 +1,27 @@
+import os
+
+enum LitheSignpost {
+    private static let signposter = OSSignposter(
+        subsystem: "com.openres.Lithe",
+        category: "Rendering"
+    )
+
+    static func begin(_ name: StaticString) -> OSSignpostIntervalState {
+        signposter.beginInterval(name)
+    }
+
+    static func end(_ name: StaticString, _ state: OSSignpostIntervalState) {
+        signposter.endInterval(name, state)
+    }
+
+    #if DEBUG
+    private static var bodyCounts: [String: Int] = [:]
+
+    static func bodyEvaluated(_ view: StaticString) {
+        bodyCounts["\(view)", default: 0] += 1
+    }
+    #else
+    @inlinable @inline(__always)
+    static func bodyEvaluated(_ view: StaticString) {}
+    #endif
+}

macos/Sources/Lithe/Views/Components/LitheDragUpdateScheduler.swift

@@ -0,0 +1,70 @@
+import Foundation
+
+/// Coalesces continuous drag updates to one delivery per main run-loop turn.
+///
+/// Held as `@State` so the bookkeeping never invalidates the host view's body.
+/// Uses `DispatchQueue.main.async` which, during `.eventTracking` mode, drains
+/// at the end of the current run-loop turn with zero added latency — unlike the
+/// 16ms `Task.sleep` pattern which adds a full frame of delay to every update.
+///
+/// `init` is `nonisolated` so that `@State` default-value initialisation —
+/// which Swift 6.2 treats as a nonisolated context — compiles without a
+/// diagnostic. All methods that access mutable state remain `@MainActor`.
+@MainActor
+final class LitheDragUpdateScheduler {
+    enum Delivery {
+        case mainRunLoopTurn
+        #if DEBUG
+        case manual
+        #endif
+    }
+
+    private var buffer = FrameCoalescedDragUpdateBuffer()
+    private var lastDeliveredValue: CGFloat?
+    private var pendingDelivery: (@MainActor () -> Void)?
+    private let delivery: Delivery
+
+    nonisolated init(delivery: Delivery = .mainRunLoopTurn) {
+        self.delivery = delivery
+    }
+
+    var pendingValue: CGFloat? { buffer.pendingValue }
+
+    func submit(
+        _ value: CGFloat,
+        minimumChange: CGFloat = 1,
+        deliver: @escaping @MainActor (CGFloat) -> Void
+    ) {
+        if let last = lastDeliveredValue, abs(value - last) < minimumChange { return }
+        guard buffer.submit(value) else { return }
+        let work: @MainActor () -> Void = { [weak self] in
+            guard let self, let value = self.buffer.takePendingValue() else { return }
+            self.lastDeliveredValue = value
+            self.pendingDelivery = nil
+            deliver(value)
+        }
+        switch delivery {
+        case .mainRunLoopTurn:
+            DispatchQueue.main.async {
+                MainActor.assumeIsolated { work() }
+            }
+        #if DEBUG
+        case .manual:
+            pendingDelivery = work
+        #endif
+        }
+    }
+
+    func cancel() {
+        buffer.cancel()
+        lastDeliveredValue = nil
+        pendingDelivery = nil
+    }
+
+    #if DEBUG
+    func flushPendingDeliveryForTesting() {
+        pendingDelivery?()
+        pendingDelivery = nil
+    }
+    #endif
+}

macos/Sources/Lithe/Views/Components/LitheSplitPaneGeometry.swift

@@ -0,0 +1,36 @@
+import CoreGraphics
+
+/// Pure geometry for split-pane resize calculations.
+enum LitheSplitPaneGeometry {
+    enum Placement {
+        case leading
+        case trailing
+    }
+
+    static func resolve(
+        start: CGFloat,
+        translation: CGFloat,
+        placement: Placement,
+        minimum: CGFloat,
+        maximum: CGFloat
+    ) -> CGFloat {
+        let raw: CGFloat
+        switch placement {
+        case .leading:
+            raw = start + translation
+        case .trailing:
+            raw = start - translation
+        }
+        return clamp(raw, minimum: minimum, maximum: maximum)
+    }
+
+    static func clamp(
+        _ value: CGFloat,
+        minimum: CGFloat,
+        maximum: CGFloat
+    ) -> CGFloat {
+        let effectiveMinimum = min(minimum, maximum)
+        let effectiveMaximum = max(minimum, maximum)
+        return min(max(value, effectiveMinimum), effectiveMaximum)
+    }
+}

macos/Sources/Lithe/Views/Components/LitheSplitPaneView.swift

@@ -0,0 +1,139 @@
+import SwiftUI
+
+/// A two-pane split whose divider drag is confined to this container.
+///
+/// One pane has a tracked size and the other takes the remainder. The dragged
+/// size lives here rather than in the hosting feature view, so moving a divider
+/// invalidates only this container: `sized` and `flexible` were built by the
+/// host's last body pass and are the same values on every re-evaluation, which
+/// lets SwiftUI skip their bodies. That is the protection `WorkbenchWorkspaceSplitView`
+/// already had and this generalizes to the Git, Run, and test tool windows.
+struct LitheSplitPaneView<Sized: View, Flexible: View>: View {
+    let axis: LitheSplitAxis
+    let placement: LitheSplitPaneGeometry.Placement
+    /// The size used until the user drags, re-supplied by the host every body
+    /// pass. Hosts that derive it from live geometry keep following the window
+    /// until the first drag, matching the pre-extraction behavior.
+    let defaultSize: CGFloat
+    let minimum: CGFloat
+    let maximum: CGFloat
+    /// Minimum size reserved for the flexible pane, when the hosted content
+    /// has a product-level usability requirement of its own.
+    let flexibleMinimum: CGFloat?
+    let showsIdleDivider: Bool
+    /// Called with the final size when a drag ends. Hosts that persist the size
+    /// write it here; the container then defers to `defaultSize` again so the
+    /// persisted value is the single source of truth.
+    let onCommit: ((CGFloat) -> Void)?
+
+    private let sized: Sized
+    private let flexible: Flexible
+
+    @State private var draggedSize: CGFloat?
+    @State private var dragStart: CGFloat = 0
+
+    init(
+        axis: LitheSplitAxis,
+        placement: LitheSplitPaneGeometry.Placement,
+        defaultSize: CGFloat,
+        minimum: CGFloat,
+        maximum: CGFloat,
+        flexibleMinimum: CGFloat? = nil,
+        showsIdleDivider: Bool = true,
+        onCommit: ((CGFloat) -> Void)? = nil,
+        @ViewBuilder sized: () -> Sized,
+        @ViewBuilder flexible: () -> Flexible
+    ) {
+        self.axis = axis
+        self.placement = placement
+        self.defaultSize = defaultSize
+        self.minimum = minimum
+        self.maximum = maximum
+        self.flexibleMinimum = flexibleMinimum
+        self.showsIdleDivider = showsIdleDivider
+        self.onCommit = onCommit
+        self.sized = sized()
+        self.flexible = flexible()
+    }
+
+    private var resolvedSize: CGFloat {
+        LitheSplitPaneGeometry.clamp(
+            draggedSize ?? defaultSize,
+            minimum: minimum,
+            maximum: maximum
+        )
+    }
+
+    var body: some View {
+        let size = resolvedSize
+        if axis == .horizontal {
+            HStack(spacing: 0) { panes(size) }
+        } else {
+            VStack(spacing: 0) { panes(size) }
+        }
+    }
+
+    @ViewBuilder
+    private func panes(_ size: CGFloat) -> some View {
+        switch placement {
+        case .leading:
+            sizedPane(size)
+            handle(size)
+            flexiblePane
+        case .trailing:
+            flexiblePane
+            handle(size)
+            sizedPane(size)
+        }
+    }
+
+    @ViewBuilder
+    private func sizedPane(_ size: CGFloat) -> some View {
+        if axis == .horizontal {
+            sized.frame(width: size)
+        } else {
+            sized.frame(height: size)
+        }
+    }
+
+    @ViewBuilder
+    private var flexiblePane: some View {
+        if axis == .horizontal {
+            flexible.frame(minWidth: flexibleMinimum, maxWidth: .infinity)
+        } else {
+            flexible.frame(minHeight: flexibleMinimum, maxHeight: .infinity)
+        }
+    }
+
+    private func handle(_ size: CGFloat) -> some View {
+        SplitHandleView(
+            axis: axis,
+            showsIdleDivider: showsIdleDivider,
+            onDragStarted: { dragStart = size },
+            onDragChanged: { translation in
+                draggedSize = resolved(from: translation)
+            },
+            onDragEnded: { translation in
+                let finalSize = resolved(from: translation)
+                if let onCommit {
+                    onCommit(finalSize)
+                    // The host now owns the value and feeds it back as
+                    // `defaultSize`; keeping a dragged size too would shadow it.
+                    draggedSize = nil
+                } else {
+                    draggedSize = finalSize
+                }
+            }
+        )
+    }
+
+    private func resolved(from translation: CGFloat) -> CGFloat {
+        LitheSplitPaneGeometry.resolve(
+            start: dragStart,
+            translation: translation,
+            placement: placement,
+            minimum: minimum,
+            maximum: maximum
+        )
+    }
+}

macos/Sources/Lithe/Views/Diff/DiffHorizontalScrollSupport.swift

@@ -12,8 +12,7 @@ struct DiffHorizontalScroller: View {
     @State private var dragStartOffset: CGFloat = 0
     @State private var isDragging = false
     @State private var isHovering = false
-    @State private var dragUpdateBuffer = FrameCoalescedDragUpdateBuffer()
-    @State private var dragUpdateTask: Task<Void, Never>?
+    @State private var dragScheduler = LitheDragUpdateScheduler()
 
     private var maximumOffset: CGFloat {
         max(0, contentWidth - viewportWidth)
@@ -53,16 +52,18 @@ struct DiffHorizontalScroller: View {
                                     dragStartOffset = offset
                                 }
                                 guard travel > 0 else { return }
-                                scheduleOffsetUpdate(constrained(
+                                dragScheduler.submit(constrained(
                                     dragStartOffset + (value.translation.width / travel) * maximumOffset
-                                ))
+                                )) { nextOffset in
+                                    offset = nextOffset
+                                }
                             }
                             .onEnded { value in
                                 if travel > 0 {
                                     let finalOffset = constrained(
                                         dragStartOffset + (value.translation.width / travel) * maximumOffset
                                     )
-                                    cancelScheduledOffsetUpdate()
+                                    dragScheduler.cancel()
                                     offset = finalOffset
                                 }
                                 isDragging = false
@@ -79,7 +80,7 @@ struct DiffHorizontalScroller: View {
         .opacity(maximumOffset > 0.5 ? 1 : 0)
         .allowsHitTesting(maximumOffset > 0.5)
         .accessibilityLabel("Synchronized diff horizontal scroll")
-        .onDisappear(perform: cancelScheduledOffsetUpdate)
+        .onDisappear { dragScheduler.cancel() }
         .onChange(of: maximumOffset) { newMaximum in
             offset = min(max(offset, 0), newMaximum)
         }
@@ -88,25 +89,6 @@ struct DiffHorizontalScroller: View {
     private func constrained(_ value: CGFloat) -> CGFloat {
         min(max(value, 0), maximumOffset)
     }
-
-    private func scheduleOffsetUpdate(_ nextOffset: CGFloat) {
-        guard dragUpdateBuffer.submit(nextOffset) else { return }
-        dragUpdateTask = Task { @MainActor in
-            try? await Task.sleep(for: .milliseconds(16))
-            guard !Task.isCancelled else { return }
-            let nextOffset = dragUpdateBuffer.takePendingValue()
-            dragUpdateTask = nil
-            if let nextOffset {
-                offset = nextOffset
-            }
-        }
-    }
-
-    private func cancelScheduledOffsetUpdate() {
-        dragUpdateTask?.cancel()
-        dragUpdateTask = nil
-        dragUpdateBuffer.cancel()
-    }
 }
 
 /// Observes horizontal trackpad/wheel gestures over the diff without becoming