From ca6f9be3818641e87d854a82646d2ea2aff6e545 Mon Sep 17 00:00:00 2001
From: Ariver <shanghai3168@gmail.com>
Date: Fri, 12 Jun 2026 12:52:43 +0800
Subject: [PATCH] Add Quick Switch view mode entry

---
 C1.source/Sources/Aligner/QuickSwitchRootView.swift | 1188 +++++++++++++++++++++++++++++++++++++++++++++++++++++-----
 1 files changed, 1,071 insertions(+), 117 deletions(-)

diff --git a/C1.source/Sources/Aligner/QuickSwitchRootView.swift b/C1.source/Sources/Aligner/QuickSwitchRootView.swift
index d8451c2..e001bc4 100644
--- a/C1.source/Sources/Aligner/QuickSwitchRootView.swift
+++ b/C1.source/Sources/Aligner/QuickSwitchRootView.swift
@@ -55,9 +55,12 @@
     private var focusedSpaceID: UInt64?
     private var debugHoveredAppGroupIndex: Int?
     private var waterfallColumns: [WaterfallColumnLayers] = []
+    private var waterfallViewMode: QuickSwitchWaterfallViewMode = .verticalColumns
     private var waterfallContentWidth: CGFloat = 0
     private var waterfallScrollOffset: CGFloat = 0
     private var waterfallColumnScrollOffsets: [Int: CGFloat] = [:]
+    private var horizontalMasonryContentHeight: CGFloat = 0
+    private var horizontalMasonryScrollOffset: CGFloat = 0
     private var currentSelection: QuickSwitchSelection?
     private var columnSelectionHistory: [Int: Int] = [:]
     private var keyboardCommandsApplied: [String] = []
@@ -78,8 +81,16 @@
     private var keyboardResponseLatencyMilliseconds: [Double] = []
     private var mouseResponseLatencyMilliseconds: [Double] = []
     private var hoverResponseLatencyMilliseconds: [Double] = []
+    private var lastProjectionTransitionMovedLayerCount = 0
+    private var lastProjectionTransitionFadeInLayerCount = 0
+    private var lastProjectionTransitionFadeOutLayerCount = 0
+    private var lastProjectionTransitionDurationMilliseconds: Double = 0
+    private var suppressEventInput = false
+    private var suppressEventBackgroundClicks = false
     var onEscape: (() -> Void)?
     var onCommitSelection: ((QuickSwitchSelection, QuickSwitchCommitSource) -> Void)?
+    var onSpaceLaneClick: ((UInt64, Int) -> Void)?
+    var onBackgroundClick: (() -> Bool)?
     var onRequestClose: ((QuickSwitchCloseRequest) -> Void)?
     var onCloseConfirmationDisabled: (() -> Void)?
 
@@ -258,6 +269,22 @@
         let closeButton: CloseButtonLayers
     }
 
+    private struct ProjectionLayerSnapshot {
+        let layer: CALayer
+        let frame: CGRect
+    }
+
+    private struct ProjectionColumnSnapshot {
+        let layer: CALayer
+        let frame: CGRect
+        let cardsByWindowID: [UInt32: ProjectionLayerSnapshot]
+    }
+
+    private struct ProjectionTransitionSnapshot {
+        let appShelfItemsByAppGroupIndex: [Int: ProjectionLayerSnapshot]
+        let waterfallColumnsByAppGroupIndex: [Int: ProjectionColumnSnapshot]
+    }
+
     private enum AppShelfMetrics {
         static let normalIconSize: CGFloat = 56
         static let hoverIconSize: CGFloat = 68
@@ -283,13 +310,25 @@
         static let columnMaxWidth: CGFloat = 292
         static let contentHorizontalPadding: CGFloat = 0
         static let columnHorizontalPadding: CGFloat = 0
-        static let columnVerticalPadding: CGFloat = 12
+        static let columnVerticalPadding: CGFloat = 0
         static let columnHeaderTextInset: CGFloat = 12
         static let headerHeight: CGFloat = 34
         static let cardHeight: CGFloat = 138
         static let cardGap: CGFloat = 12
         static let revealPadding: CGFloat = 24
         static let horizontalRevealPadding: CGFloat = 0
+    }
+
+    private enum HorizontalMasonryMetrics {
+        static let horizontalPadding: CGFloat = 12
+        static let verticalPadding: CGFloat = 0
+        static let cardGap: CGFloat = 16
+        static let cardMinWidth: CGFloat = 220
+        static let cardMaxWidth: CGFloat = 320
+        static let titleBarHeight: CGFloat = 26
+        static let titleGap: CGFloat = 6
+        static let minThumbnailHeight: CGFloat = 92
+        static let maxThumbnailHeightFraction: CGFloat = 0.40
     }
 
     private enum WaterfallHorizontalIntent {
@@ -304,11 +343,11 @@
     }
 
     private enum SpaceLaneMetrics {
-        static let horizontalPadding: CGFloat = 12
-        static let groupGap: CGFloat = 30
-        static let groupHorizontalPadding: CGFloat = 12
-        static let groupVerticalPadding: CGFloat = 10
-        static let segmentGap: CGFloat = 10
+        static let horizontalPadding: CGFloat = 0
+        static let groupGap: CGFloat = 36
+        static let groupHorizontalPadding: CGFloat = 24
+        static let groupVerticalPadding: CGFloat = 6
+        static let segmentGap: CGFloat = 12
         static let segmentMinWidth: CGFloat = 96
         static let segmentMaxWidth: CGFloat = 150
     }
@@ -358,6 +397,13 @@
     }
 
     override func keyDown(with event: NSEvent) {
+        if suppressEventInput {
+            DevelopmentDiagnostics.log("quickSwitch.view.keyDown.ignoredForDebugSequence", [
+                "keyCode": event.keyCode
+            ])
+            return
+        }
+
         switch event.keyCode {
         case TriggerKeyCode.escape where Self.shouldDismissOnEscape(event):
             onEscape?()
@@ -400,6 +446,15 @@
         }
 
         if shouldScrollWaterfall(for: event) {
+            if isHorizontalMasonryMode {
+                let currentOffset = horizontalMasonryScrollOffset
+                horizontalMasonryScrollOffset = clampedHorizontalMasonryOffset(
+                    currentOffset - event.scrollingDeltaY
+                )
+                needsLayout = true
+                return
+            }
+
             if abs(event.scrollingDeltaX) >= abs(event.scrollingDeltaY), waterfallAlignmentScrollable {
                 waterfallScrollOffset = clampedWaterfallAlignmentOffset(waterfallScrollOffset - event.scrollingDeltaX)
                 needsLayout = true
@@ -441,6 +496,15 @@
     }
 
     override func mouseDown(with event: NSEvent) {
+        if suppressEventInput {
+            DevelopmentDiagnostics.log("quickSwitch.view.mouseDown.ignoredForDebugSequence", [
+                "x": event.locationInWindow.x,
+                "y": event.locationInWindow.y,
+                "bounds": NSStringFromRect(bounds)
+            ])
+            return
+        }
+
         if handleCloseConfirmationMouseDown(at: event.locationInWindow) {
             return
         }
@@ -456,7 +520,7 @@
         }
 
         if let segment = spaceLaneSegment(at: event.locationInWindow) {
-            clickSpaceLaneSegment(segment)
+            clickSpaceLaneSegment(segment, clickCount: max(1, event.clickCount))
             return
         }
 
@@ -470,6 +534,9 @@
             "y": event.locationInWindow.y,
             "bounds": NSStringFromRect(bounds)
         ])
+        if !suppressEventBackgroundClicks, onBackgroundClick?() == true {
+            return
+        }
         super.mouseDown(with: event)
     }
 
@@ -513,6 +580,15 @@
         }
     }
 
+    func setSuppressEventBackgroundClicks(_ suppressed: Bool) {
+        suppressEventBackgroundClicks = suppressed
+    }
+
+    func setSuppressEventInput(_ suppressed: Bool) {
+        suppressEventInput = suppressed
+        suppressEventBackgroundClicks = suppressed
+    }
+
     func beginPerformanceFirstFrameMeasurement() {
         firstFrameMeasurementStart = CACurrentMediaTime()
     }
@@ -543,6 +619,17 @@
             closeConfirmationLayers.containerLayer.isHidden = true
             closeConfirmationArrowEdge = nil
         }
+        needsLayout = true
+    }
+
+    func setWaterfallViewMode(_ mode: QuickSwitchWaterfallViewMode) {
+        guard waterfallViewMode != mode else { return }
+
+        waterfallViewMode = mode
+        waterfallScrollOffset = 0
+        waterfallColumnScrollOffsets = [:]
+        horizontalMasonryScrollOffset = 0
+        horizontalMasonryContentHeight = 0
         needsLayout = true
     }
 
@@ -608,35 +695,77 @@
         }
     }
 
+    func effectiveSelectionForProjection() -> QuickSwitchSelection? {
+        effectiveSelection
+    }
+
     func apply(viewModel: QuickSwitchViewModel?) {
+        apply(viewModel: viewModel, preservingInteractionState: false, animatedProjection: false)
+    }
+
+    func applyProjected(viewModel: QuickSwitchViewModel?) {
+        apply(viewModel: viewModel, preservingInteractionState: true, animatedProjection: true)
+    }
+
+    private func apply(
+        viewModel: QuickSwitchViewModel?,
+        preservingInteractionState: Bool,
+        animatedProjection: Bool
+    ) {
+        let transitionSnapshot = animatedProjection ? captureProjectionTransitionSnapshot() : nil
+        if !animatedProjection {
+            resetProjectionTransitionReport()
+        }
         currentViewModel = viewModel
-        screenshotSourcesByWindowID = [:]
-        screenshotSkippedReasonsByWindowID = [:]
-        currentSelection = viewModel?.initialSelection
-        columnSelectionHistory = [:]
-        keyboardCommandsApplied = []
-        lastKeyboardCommand = nil
-        tabIgnoredCount = 0
-        lastCommittedSelection = nil
-        lastCommitSource = nil
-        mouseCommandsApplied = []
-        lastMouseCommand = nil
-        lastClickedAppGroupIndex = nil
-        lastAppShelfClickChangedSelection = nil
-        lastClickedWindowID = nil
-        lastSpaceFocusedAppGroupIndex = nil
-        lastSpaceLaneClickSpaceID = nil
-        lastAppShelfScrollSyncedAppGroupIndex = nil
-        focusedSpaceID = nil
-        hoveredCloseTarget = nil
-        pendingCloseTarget = nil
-        pendingCloseRequest = nil
-        pendingCloseOptOut = false
-        closeConfirmationLayers.containerLayer.isHidden = true
-        closeConfirmationArrowEdge = nil
-        clearCloseFeedback()
-        setHoverTarget(.none)
-        hoveredAppGroupIndex = debugHoveredAppGroupIndex
+
+        if preservingInteractionState {
+            currentSelection = validSelection(currentSelection, in: viewModel) ?? viewModel?.initialSelection
+            columnSelectionHistory = columnSelectionHistory.filter { appGroupIndex, _ in
+                viewModel?.waterfallColumns.contains { $0.appGroupIndex == appGroupIndex } == true
+            }
+            if let currentSelection {
+                columnSelectionHistory[currentSelection.appGroupIndex] = currentSelection.windowIndex
+            }
+            hoveredCloseTarget = nil
+            pendingCloseTarget = nil
+            pendingCloseRequest = nil
+            pendingCloseOptOut = false
+            closeConfirmationLayers.containerLayer.isHidden = true
+            closeConfirmationArrowEdge = nil
+        } else {
+            screenshotSourcesByWindowID = [:]
+            screenshotSkippedReasonsByWindowID = [:]
+            currentSelection = viewModel?.initialSelection
+            columnSelectionHistory = [:]
+            keyboardCommandsApplied = []
+            lastKeyboardCommand = nil
+            tabIgnoredCount = 0
+            lastCommittedSelection = nil
+            lastCommitSource = nil
+            mouseCommandsApplied = []
+            lastMouseCommand = nil
+            lastClickedAppGroupIndex = nil
+            lastAppShelfClickChangedSelection = nil
+            lastClickedWindowID = nil
+            lastSpaceFocusedAppGroupIndex = nil
+            lastSpaceLaneClickSpaceID = nil
+            lastAppShelfScrollSyncedAppGroupIndex = nil
+            waterfallScrollOffset = 0
+            waterfallColumnScrollOffsets = [:]
+            horizontalMasonryScrollOffset = 0
+            horizontalMasonryContentHeight = 0
+            focusedSpaceID = nil
+            hoveredCloseTarget = nil
+            pendingCloseTarget = nil
+            pendingCloseRequest = nil
+            pendingCloseOptOut = false
+            closeConfirmationLayers.containerLayer.isHidden = true
+            closeConfirmationArrowEdge = nil
+            clearCloseFeedback()
+            setHoverTarget(.none)
+            hoveredAppGroupIndex = debugHoveredAppGroupIndex
+        }
+
         if let currentSelection {
             columnSelectionHistory[currentSelection.appGroupIndex] = currentSelection.windowIndex
         }
@@ -646,6 +775,250 @@
         needsLayout = true
         ensureCurrentSelectionVisible(horizontalIntent: .alignWithAppShelf(animated: false))
         needsLayout = true
+        if animatedProjection, let transitionSnapshot {
+            layoutSubtreeIfNeeded()
+            applyProjectionTransitionAnimations(from: transitionSnapshot)
+        }
+    }
+
+    private func validSelection(
+        _ selection: QuickSwitchSelection?,
+        in viewModel: QuickSwitchViewModel?
+    ) -> QuickSwitchSelection? {
+        guard let selection, let viewModel else { return nil }
+
+        for column in viewModel.waterfallColumns {
+            if let card = column.windows.first(where: { $0.window.id == selection.windowID }) {
+                return QuickSwitchSelection(
+                    appGroupIndex: card.appGroupIndex,
+                    windowIndex: card.windowIndex,
+                    windowID: card.window.id
+                )
+            }
+        }
+
+        return nil
+    }
+
+    private func captureProjectionTransitionSnapshot() -> ProjectionTransitionSnapshot {
+        ProjectionTransitionSnapshot(
+            appShelfItemsByAppGroupIndex: Dictionary(
+                uniqueKeysWithValues: appShelfItems.map { item in
+                    (
+                        item.item.appGroupIndex,
+                        ProjectionLayerSnapshot(
+                            layer: item.containerLayer,
+                            frame: item.containerLayer.frame
+                        )
+                    )
+                }
+            ),
+            waterfallColumnsByAppGroupIndex: Dictionary(
+                uniqueKeysWithValues: waterfallColumns.map { column in
+                    (
+                        column.column.appGroupIndex,
+                        ProjectionColumnSnapshot(
+                            layer: column.containerLayer,
+                            frame: column.containerLayer.frame,
+                            cardsByWindowID: Dictionary(
+                                uniqueKeysWithValues: column.cards.map { card in
+                                    (
+                                        card.item.window.id,
+                                        ProjectionLayerSnapshot(
+                                            layer: card.containerLayer,
+                                            frame: card.containerLayer.frame
+                                        )
+                                    )
+                                }
+                            )
+                        )
+                    )
+                }
+            )
+        )
+    }
+
+    private func applyProjectionTransitionAnimations(from snapshot: ProjectionTransitionSnapshot) {
+        let reduceMotion = NSWorkspace.shared.accessibilityDisplayShouldReduceMotion
+        let duration: CFTimeInterval = reduceMotion ? 0.12 : 0.21
+        let timing = CAMediaTimingFunction(name: reduceMotion ? .linear : .easeOut)
+        var movedLayerCount = 0
+        var fadeInLayerCount = 0
+        var fadeOutLayerCount = 0
+
+        for item in appShelfItems {
+            guard let oldSnapshot = snapshot.appShelfItemsByAppGroupIndex[item.item.appGroupIndex] else {
+                if addFadeInAnimation(to: item.containerLayer, duration: duration, timing: timing) {
+                    fadeInLayerCount += 1
+                }
+                continue
+            }
+            if addPositionAnimation(to: item.containerLayer, from: oldSnapshot.frame, duration: duration, timing: timing) {
+                movedLayerCount += 1
+            }
+        }
+
+        let visibleAppGroupIndexes = Set(appShelfItems.map(\.item.appGroupIndex))
+        for (appGroupIndex, oldSnapshot) in snapshot.appShelfItemsByAppGroupIndex
+            where !visibleAppGroupIndexes.contains(appGroupIndex) {
+            if addFadeOutSnapshot(
+                oldSnapshot,
+                to: appShelfContentLayer,
+                frame: oldSnapshot.frame,
+                duration: duration,
+                timing: timing
+            ) {
+                fadeOutLayerCount += 1
+            }
+        }
+
+        for column in waterfallColumns {
+            guard let oldSnapshot = snapshot.waterfallColumnsByAppGroupIndex[column.column.appGroupIndex] else {
+                if addFadeInAnimation(to: column.containerLayer, duration: duration, timing: timing) {
+                    fadeInLayerCount += 1
+                }
+                continue
+            }
+            if addPositionAnimation(to: column.containerLayer, from: oldSnapshot.frame, duration: duration, timing: timing) {
+                movedLayerCount += 1
+            }
+
+            for card in column.cards {
+                guard let oldCardSnapshot = oldSnapshot.cardsByWindowID[card.item.window.id] else {
+                    if addFadeInAnimation(to: card.containerLayer, duration: duration, timing: timing) {
+                        fadeInLayerCount += 1
+                    }
+                    continue
+                }
+                if addPositionAnimation(to: card.containerLayer, from: oldCardSnapshot.frame, duration: duration, timing: timing) {
+                    movedLayerCount += 1
+                }
+            }
+        }
+
+        let visibleColumnsByAppGroupIndex = Dictionary(
+            uniqueKeysWithValues: waterfallColumns.map { ($0.column.appGroupIndex, $0) }
+        )
+        for (appGroupIndex, oldSnapshot) in snapshot.waterfallColumnsByAppGroupIndex {
+            guard let visibleColumn = visibleColumnsByAppGroupIndex[appGroupIndex] else {
+                if addFadeOutSnapshot(
+                    ProjectionLayerSnapshot(layer: oldSnapshot.layer, frame: oldSnapshot.frame),
+                    to: waterfallContentLayer,
+                    frame: oldSnapshot.frame,
+                    duration: duration,
+                    timing: timing
+                ) {
+                    fadeOutLayerCount += 1
+                }
+                continue
+            }
+
+            let visibleWindowIDs = Set(visibleColumn.cards.map(\.item.window.id))
+            for (windowID, oldCardSnapshot) in oldSnapshot.cardsByWindowID
+                where !visibleWindowIDs.contains(windowID) {
+                let absoluteFrame = oldCardSnapshot.frame.offsetBy(
+                    dx: oldSnapshot.frame.minX,
+                    dy: oldSnapshot.frame.minY
+                )
+                if addFadeOutSnapshot(
+                    oldCardSnapshot,
+                    to: waterfallContentLayer,
+                    frame: absoluteFrame,
+                    duration: duration,
+                    timing: timing
+                ) {
+                    fadeOutLayerCount += 1
+                }
+            }
+        }
+
+        lastProjectionTransitionMovedLayerCount = movedLayerCount
+        lastProjectionTransitionFadeInLayerCount = fadeInLayerCount
+        lastProjectionTransitionFadeOutLayerCount = fadeOutLayerCount
+        lastProjectionTransitionDurationMilliseconds = duration * 1_000
+    }
+
+    private func resetProjectionTransitionReport() {
+        lastProjectionTransitionMovedLayerCount = 0
+        lastProjectionTransitionFadeInLayerCount = 0
+        lastProjectionTransitionFadeOutLayerCount = 0
+        lastProjectionTransitionDurationMilliseconds = 0
+    }
+
+    @discardableResult
+    private func addPositionAnimation(
+        to layer: CALayer,
+        from oldFrame: CGRect,
+        duration: CFTimeInterval,
+        timing: CAMediaTimingFunction
+    ) -> Bool {
+        let oldPosition = CGPoint(x: oldFrame.midX, y: oldFrame.midY)
+        let newPosition = layer.position
+        guard abs(oldPosition.x - newPosition.x) > 0.5 || abs(oldPosition.y - newPosition.y) > 0.5 else {
+            return false
+        }
+
+        let animation = CABasicAnimation(keyPath: "position")
+        animation.fromValue = oldPosition
+        animation.toValue = newPosition
+        animation.duration = duration
+        animation.timingFunction = timing
+        animation.isRemovedOnCompletion = true
+        layer.add(animation, forKey: "quickSwitchProjectionPosition")
+        return true
+    }
+
+    @discardableResult
+    private func addFadeInAnimation(
+        to layer: CALayer,
+        duration: CFTimeInterval,
+        timing: CAMediaTimingFunction
+    ) -> Bool {
+        let animation = CABasicAnimation(keyPath: "opacity")
+        animation.fromValue = 0
+        animation.toValue = layer.opacity
+        animation.duration = duration
+        animation.timingFunction = timing
+        animation.isRemovedOnCompletion = true
+        layer.add(animation, forKey: "quickSwitchProjectionFadeIn")
+        return true
+    }
+
+    @discardableResult
+    private func addFadeOutSnapshot(
+        _ snapshot: ProjectionLayerSnapshot,
+        to parentLayer: CALayer,
+        frame: CGRect,
+        duration: CFTimeInterval,
+        timing: CAMediaTimingFunction
+    ) -> Bool {
+        let layer = snapshot.layer
+        layer.removeAllAnimations()
+        layer.removeFromSuperlayer()
+        CATransaction.begin()
+        CATransaction.setDisableActions(true)
+        layer.frame = frame
+        layer.opacity = max(layer.opacity, 0.01)
+        layer.zPosition = max(layer.zPosition, 240)
+        parentLayer.addSublayer(layer)
+        CATransaction.commit()
+
+        let animation = CABasicAnimation(keyPath: "opacity")
+        animation.fromValue = layer.opacity
+        animation.toValue = 0
+        animation.duration = duration
+        animation.timingFunction = timing
+        animation.isRemovedOnCompletion = true
+        CATransaction.begin()
+        CATransaction.setDisableActions(true)
+        layer.opacity = 0
+        CATransaction.commit()
+        layer.add(animation, forKey: "quickSwitchProjectionFadeOut")
+
+        DispatchQueue.main.asyncAfter(deadline: .now() + duration + 0.05) { [weak layer] in
+            layer?.removeFromSuperlayer()
+        }
+        return true
     }
 
     func reportDictionary() -> [String: Any] {
@@ -669,6 +1042,8 @@
             "glassBorderWidth": Double(glassLayer.borderWidth),
             "glassShadowOpacity": Double(glassLayer.shadowOpacity),
             "spaceLaneFrame": dictionary(from: laneLayer.frame),
+            "spaceLaneBackgroundColor": colorDictionary(from: laneLayer.backgroundColor),
+            "spaceLaneCornerRadius": Double(laneLayer.cornerRadius),
             "spaceLaneContentWidth": Double(spaceLaneContentWidth),
             "spaceLaneVisibleWidth": Double(laneLayer.bounds.width),
             "spaceLaneMaxScrollOffset": Double(spaceLaneMaxScrollOffset),
@@ -683,6 +1058,8 @@
             "spaceLaneHoveredSpaceID": hoveredSpaceLaneID ?? NSNull(),
             "spaceLaneFocusedSpaceID": focusedSpaceID ?? NSNull(),
             "activeSpaceFocusID": activeSpaceFocusID ?? NSNull(),
+            "spaceFilterLockedSpaceID": currentViewModel?.lockedSpaceID ?? NSNull(),
+            "spaceFilterActive": currentViewModel?.lockedSpaceID != nil,
             "spaceFocusAppGroupIndexes": spaceFocusedAppGroupIndexes(),
             "appHoverAssociatedSpaceIDs": appHoverAssociatedSpaceIDs.sorted(),
             "appHoverAssociatedSpaceLabels": appHoverAssociatedSpaceLabels,
@@ -714,13 +1091,19 @@
             "appShelfMinIconSize": Double(AppShelfMetrics.minIconSize),
             "appShelfItems": appShelfItemReports(),
             "waterfallFrame": dictionary(from: waterfallLayer.frame),
+            "waterfallViewMode": waterfallViewMode.rawValue,
             "waterfallContentWidth": Double(waterfallContentWidth),
             "waterfallVisibleWidth": Double(waterfallLayer.bounds.width),
             "waterfallScrollOffset": Double(waterfallScrollOffset),
             "waterfallMaxScrollOffset": Double(waterfallMaxScrollOffset),
+            "horizontalMasonryContentHeight": Double(horizontalMasonryContentHeight),
+            "horizontalMasonryScrollOffset": Double(horizontalMasonryScrollOffset),
+            "horizontalMasonryMaxScrollOffset": Double(horizontalMasonryMaxScrollOffset),
+            "horizontalMasonryScrollable": horizontalMasonryMaxScrollOffset > 0,
             "waterfallAlignmentMinScrollOffset": Double(waterfallAlignmentScrollRange.lowerBound),
             "waterfallAlignmentMaxScrollOffset": Double(waterfallAlignmentScrollRange.upperBound),
-            "waterfallScrollable": waterfallAlignmentScrollable,
+            "waterfallScrollable": waterfallMaxScrollOffset > 0,
+            "waterfallAlignmentScrollable": waterfallAlignmentScrollable,
             "waterfallColumnCount": waterfallColumns.count,
             "waterfallColumnNames": waterfallColumns.map(\.column.app.name),
             "waterfallClipsToBounds": waterfallLayer.masksToBounds,
@@ -729,6 +1112,10 @@
             "waterfallAlignmentTolerance": Double(WaterfallAlignmentMetrics.tolerance),
             "waterfallAlignmentAnimationDurationMilliseconds": Double(WaterfallAlignmentMetrics.animationDuration * 1_000),
             "waterfallAlignmentAnimationTimingName": "easeOut",
+            "projectionTransitionMovedLayerCount": lastProjectionTransitionMovedLayerCount,
+            "projectionTransitionFadeInLayerCount": lastProjectionTransitionFadeInLayerCount,
+            "projectionTransitionFadeOutLayerCount": lastProjectionTransitionFadeOutLayerCount,
+            "projectionTransitionDurationMilliseconds": lastProjectionTransitionDurationMilliseconds,
             "reduceMotionEffective": NSWorkspace.shared.accessibilityDisplayShouldReduceMotion,
             "selectedAppGroupIndex": effectiveSelection?.appGroupIndex ?? NSNull(),
             "selectedWindowIndex": effectiveSelection?.windowIndex ?? NSNull(),
@@ -824,8 +1211,13 @@
             recordKeyboardCommand("enter")
             commitCurrentSelection()
         case "tab":
-            tabIgnoredCount += 1
-            recordKeyboardCommand("tabIgnored")
+            if isHorizontalMasonryMode {
+                recordKeyboardCommand("tab")
+                moveSelection(.right)
+            } else {
+                tabIgnoredCount += 1
+                recordKeyboardCommand("tabIgnored")
+            }
         default:
             recordKeyboardCommand("unknown:\(command)")
         }
@@ -895,8 +1287,21 @@
             }
             recordMouseCommand("click-space:\(spaceID)")
             if let segment = spaceLaneSegment(spaceID: spaceID) {
-                clickSpaceLaneSegment(segment)
+                clickSpaceLaneSegment(segment, clickCount: 1)
             }
+        case "double-click-space" where parts.count == 2:
+            guard let spaceID = UInt64(parts[1]) else {
+                recordMouseCommand("invalid:\(command)")
+                return
+            }
+            recordMouseCommand("double-click-space:\(spaceID)")
+            if let segment = spaceLaneSegment(spaceID: spaceID) {
+                clickSpaceLaneSegment(segment, clickCount: 1)
+                clickSpaceLaneSegment(segment, clickCount: 2)
+            }
+        case "click-background":
+            recordMouseCommand("click-background")
+            _ = onBackgroundClick?()
         case "hover-card" where parts.count == 3:
             guard let appGroupIndex = Int(parts[1]), let windowIndex = Int(parts[2]) else {
                 recordMouseCommand("invalid:\(command)")
@@ -1012,22 +1417,15 @@
         focusSpace(segment.space.id, persistent: false, source: source)
     }
 
-    private func clickSpaceLaneSegment(_ segment: SpaceLaneSegmentLayers) {
+    private func clickSpaceLaneSegment(_ segment: SpaceLaneSegmentLayers, clickCount: Int = 1) {
         DevelopmentDiagnostics.log("quickSwitch.view.clickSpaceLane", [
             "spaceID": segment.space.id,
-            "label": segment.space.label
+            "label": segment.space.label,
+            "clickCount": clickCount
         ])
         lastSpaceLaneClickSpaceID = segment.space.id
-
-        guard let firstCard = firstWaterfallCard(inSpaceID: segment.space.id) else {
-            DevelopmentDiagnostics.log("quickSwitch.view.clickSpaceLane.emptySpaceUnsupported", [
-                "spaceID": segment.space.id,
-                "label": segment.space.label
-            ])
-            return
-        }
-
-        commitWindowCard(firstCard, trigger: "spaceLane")
+        onSpaceLaneClick?(segment.space.id, clickCount)
+        lastSpaceLaneClickSpaceID = segment.space.id
     }
 
     private func focusSpace(_ spaceID: UInt64, persistent: Bool, source: HoverTargetSource = .event) {
@@ -1225,6 +1623,11 @@
     }
 
     private func moveSelection(_ direction: QuickSwitchKeyboardDirection) {
+        if isHorizontalMasonryMode {
+            moveHorizontalMasonrySelection(direction)
+            return
+        }
+
         guard let currentViewModel,
               let snapshot = snapshotForFocus(from: currentViewModel),
               let current = currentSelection ?? currentViewModel.initialSelection,
@@ -1254,6 +1657,113 @@
             "windowID": next.windowID
         ])
         needsLayout = true
+    }
+
+    private func moveHorizontalMasonrySelection(_ direction: QuickSwitchKeyboardDirection) {
+        guard let current = currentSelection ?? currentViewModel?.initialSelection,
+              let next = nextHorizontalMasonrySelection(from: current, direction: direction)
+        else {
+            DevelopmentDiagnostics.log("quickSwitch.view.moveHorizontalMasonrySelection.blocked", [
+                "direction": String(describing: direction),
+                "hasSelection": (currentSelection ?? currentViewModel?.initialSelection) != nil
+            ])
+            return
+        }
+
+        columnSelectionHistory[current.appGroupIndex] = current.windowIndex
+        currentSelection = next
+        columnSelectionHistory[next.appGroupIndex] = next.windowIndex
+        ensureCurrentSelectionVisible(horizontalIntent: .alignWithAppShelf(animated: true))
+        DevelopmentDiagnostics.log("quickSwitch.view.moveHorizontalMasonrySelection", [
+            "direction": String(describing: direction),
+            "appGroupIndex": next.appGroupIndex,
+            "windowIndex": next.windowIndex,
+            "windowID": next.windowID
+        ])
+        needsLayout = true
+    }
+
+    private func nextHorizontalMasonrySelection(
+        from current: QuickSwitchSelection,
+        direction: QuickSwitchKeyboardDirection
+    ) -> QuickSwitchSelection? {
+        layoutSubtreeIfNeeded()
+
+        let cards = horizontalMasonryCardsInPlacementOrder()
+        guard let currentIndex = cards.firstIndex(where: { $0.item.window.id == current.windowID }) else {
+            return cards.first.map(selectionForCard)
+        }
+
+        switch direction {
+        case .right:
+            return selectionForCard(cards[(currentIndex + 1) % cards.count])
+        case .left:
+            return selectionForCard(cards[(currentIndex - 1 + cards.count) % cards.count])
+        case .up:
+            return nearestHorizontalMasonrySelection(from: cards[currentIndex], direction: .up)
+                ?? selectionForCard(cards.first ?? cards[currentIndex])
+        case .down:
+            return nearestHorizontalMasonrySelection(from: cards[currentIndex], direction: .down)
+                ?? selectionForCard(cards.last ?? cards[currentIndex])
+        }
+    }
+
+    private func nearestHorizontalMasonrySelection(
+        from currentCard: WaterfallCardLayers,
+        direction: QuickSwitchKeyboardDirection
+    ) -> QuickSwitchSelection? {
+        let currentFrame = currentCard.containerLayer.frame
+        let candidates = horizontalMasonryCardsInPlacementOrder().filter { card in
+            guard card.item.window.id != currentCard.item.window.id else { return false }
+            switch direction {
+            case .up:
+                return card.containerLayer.frame.minY >= currentFrame.maxY - 0.5
+            case .down:
+                return card.containerLayer.frame.maxY <= currentFrame.minY + 0.5
+            case .left, .right:
+                return false
+            }
+        }
+
+        let best = candidates.min { lhs, rhs in
+            let lhsFrame = lhs.containerLayer.frame
+            let rhsFrame = rhs.containerLayer.frame
+            let lhsPrimaryDistance = direction == .up
+                ? lhsFrame.minY - currentFrame.maxY
+                : currentFrame.minY - lhsFrame.maxY
+            let rhsPrimaryDistance = direction == .up
+                ? rhsFrame.minY - currentFrame.maxY
+                : currentFrame.minY - rhsFrame.maxY
+            if abs(lhsPrimaryDistance - rhsPrimaryDistance) > 0.5 {
+                return lhsPrimaryDistance < rhsPrimaryDistance
+            }
+
+            let lhsHorizontalDistance = abs(lhsFrame.midX - currentFrame.midX)
+            let rhsHorizontalDistance = abs(rhsFrame.midX - currentFrame.midX)
+            if abs(lhsHorizontalDistance - rhsHorizontalDistance) > 0.5 {
+                return lhsHorizontalDistance < rhsHorizontalDistance
+            }
+
+            return lhs.item.globalIndex < rhs.item.globalIndex
+        }
+
+        return best.map(selectionForCard)
+    }
+
+    private func horizontalMasonryCardsInPlacementOrder() -> [WaterfallCardLayers] {
+        waterfallColumns
+            .sorted { $0.column.appGroupIndex < $1.column.appGroupIndex }
+            .flatMap { column in
+                column.cards.sorted { $0.item.windowIndex < $1.item.windowIndex }
+            }
+    }
+
+    private func selectionForCard(_ card: WaterfallCardLayers) -> QuickSwitchSelection {
+        QuickSwitchSelection(
+            appGroupIndex: card.item.appGroupIndex,
+            windowIndex: card.item.windowIndex,
+            windowID: card.item.window.id
+        )
     }
 
     private func commitCurrentSelection() {
@@ -1313,9 +1823,24 @@
         _ selection: QuickSwitchSelection,
         horizontalIntent: WaterfallHorizontalIntent = .reveal
     ) {
+        if isHorizontalMasonryMode {
+            switch horizontalIntent {
+            case .reveal:
+                ensureHorizontalMasonrySelectionVisible(selection, animated: false)
+            case .alignWithAppShelf(let animated):
+                ensureHorizontalMasonrySelectionVisible(selection, animated: animated)
+            }
+            return
+        }
+
         guard
             let column = waterfallColumns.first(where: { $0.column.appGroupIndex == selection.appGroupIndex })
         else {
+            return
+        }
+
+        if waterfallShouldKeepFilteredColumnsCentered {
+            ensureWaterfallCardVisibleVertically(selection)
             return
         }
 
@@ -1329,6 +1854,11 @@
     }
 
     private func ensureWaterfallCardVisibleVertically(_ selection: QuickSwitchSelection) {
+        guard !isHorizontalMasonryMode else {
+            ensureHorizontalMasonrySelectionVisible(selection, animated: false)
+            return
+        }
+
         let visibleHeight = max(
             1,
             waterfallLayer.bounds.height
@@ -1356,6 +1886,11 @@
     }
 
     private func alignWaterfallColumnWithAppShelfIcon(appGroupIndex: Int, animated: Bool) {
+        if isHorizontalMasonryMode {
+            ensureHorizontalMasonryAppVisible(appGroupIndex, animated: animated)
+            return
+        }
+
         guard
             let item = appShelfItems.first(where: { $0.item.appGroupIndex == appGroupIndex }),
             let column = waterfallColumns.first(where: { $0.column.appGroupIndex == appGroupIndex })
@@ -1382,6 +1917,11 @@
     }
 
     private func ensureWaterfallColumnVisible(_ appGroupIndex: Int) {
+        if isHorizontalMasonryMode {
+            ensureHorizontalMasonryAppVisible(appGroupIndex, animated: false)
+            return
+        }
+
         guard let column = waterfallColumns.first(where: { $0.column.appGroupIndex == appGroupIndex }) else {
             return
         }
@@ -1390,6 +1930,11 @@
     }
 
     private func ensureWaterfallColumnVisible(_ column: WaterfallColumnLayers) {
+        if isHorizontalMasonryMode {
+            ensureHorizontalMasonryAppVisible(column.column.appGroupIndex, animated: false)
+            return
+        }
+
         waterfallScrollOffset = clampedWaterfallOffset(
             scrollOffset(
                 makingVisible: column.containerLayer.frame,
@@ -1402,6 +1947,14 @@
     }
 
     private var waterfallAlignmentScrollRange: ClosedRange<CGFloat> {
+        if isHorizontalMasonryMode {
+            return 0...0
+        }
+
+        if waterfallShouldKeepFilteredColumnsCentered {
+            return 0...0
+        }
+
         var minimumOffset: CGFloat = 0
         var maximumOffset = waterfallMaxScrollOffset
 
@@ -1426,6 +1979,10 @@
     private func clampedWaterfallAlignmentOffset(_ offset: CGFloat) -> CGFloat {
         let range = waterfallAlignmentScrollRange
         return min(max(range.lowerBound, offset), range.upperBound)
+    }
+
+    private var waterfallShouldKeepFilteredColumnsCentered: Bool {
+        currentViewModel?.lockedSpaceID != nil && waterfallMaxScrollOffset <= 0.5
     }
 
     private func setWaterfallScrollOffset(_ offset: CGFloat, animated: Bool) {
@@ -1460,6 +2017,80 @@
         animation.timingFunction = CAMediaTimingFunction(name: WaterfallAlignmentMetrics.animationTimingName)
         animation.isRemovedOnCompletion = true
         waterfallContentLayer.add(animation, forKey: "waterfallColumnAlignment")
+    }
+
+    private func ensureHorizontalMasonrySelectionVisible(
+        _ selection: QuickSwitchSelection,
+        animated: Bool
+    ) {
+        guard let card = waterfallCard(
+            appGroupIndex: selection.appGroupIndex,
+            windowIndex: selection.windowIndex
+        ) else {
+            return
+        }
+
+        let visibleFrame = card.containerLayer.frame.offsetBy(
+            dx: 0,
+            dy: waterfallContentLayer.frame.minY
+        )
+        let visibleHeight = waterfallLayer.bounds.height
+        let padding = WaterfallMetrics.revealPadding
+        var nextOffset = horizontalMasonryScrollOffset
+
+        if visibleFrame.maxY > visibleHeight - padding {
+            nextOffset -= visibleFrame.maxY - (visibleHeight - padding)
+        } else if visibleFrame.minY < padding {
+            nextOffset += padding - visibleFrame.minY
+        }
+
+        setHorizontalMasonryScrollOffset(nextOffset, animated: animated)
+    }
+
+    private func ensureHorizontalMasonryAppVisible(_ appGroupIndex: Int, animated: Bool) {
+        guard let firstCard = waterfallColumns
+            .first(where: { $0.column.appGroupIndex == appGroupIndex })?
+            .cards
+            .sorted(by: { $0.item.windowIndex < $1.item.windowIndex })
+            .first
+        else {
+            return
+        }
+
+        let cardTopDistance = horizontalMasonryContentHeight - firstCard.containerLayer.frame.maxY
+        setHorizontalMasonryScrollOffset(
+            cardTopDistance - WaterfallMetrics.revealPadding,
+            animated: animated
+        )
+    }
+
+    private func setHorizontalMasonryScrollOffset(_ offset: CGFloat, animated: Bool) {
+        let nextOffset = clampedHorizontalMasonryOffset(offset)
+        let previousPositionY = waterfallContentLayer.presentation()?.position.y
+            ?? waterfallContentLayer.position.y
+
+        horizontalMasonryScrollOffset = nextOffset
+        CATransaction.begin()
+        CATransaction.setDisableActions(true)
+        waterfallContentLayer.frame = horizontalMasonryContentFrame()
+        CATransaction.commit()
+
+        let nextPositionY = waterfallContentLayer.position.y
+        guard animated,
+              !NSWorkspace.shared.accessibilityDisplayShouldReduceMotion,
+              abs(previousPositionY - nextPositionY) > 0.5
+        else {
+            waterfallContentLayer.removeAnimation(forKey: "horizontalMasonryAlignment")
+            return
+        }
+
+        let animation = CABasicAnimation(keyPath: "position.y")
+        animation.fromValue = previousPositionY
+        animation.toValue = nextPositionY
+        animation.duration = WaterfallAlignmentMetrics.animationDuration
+        animation.timingFunction = CAMediaTimingFunction(name: WaterfallAlignmentMetrics.animationTimingName)
+        animation.isRemovedOnCompletion = true
+        waterfallContentLayer.add(animation, forKey: "horizontalMasonryAlignment")
     }
 
     private func scrollOffset(
@@ -1576,8 +2207,8 @@
         glassLayer.shadowOpacity = 0
         rootLayer.addSublayer(glassLayer)
 
-        laneLayer.backgroundColor = NSColor.controlBackgroundColor.withAlphaComponent(0.68).cgColor
-        laneLayer.cornerRadius = 16
+        laneLayer.backgroundColor = NSColor.clear.cgColor
+        laneLayer.cornerRadius = 0
         laneLayer.masksToBounds = true
         glassLayer.addSublayer(laneLayer)
         laneLayer.addSublayer(spaceLaneContentLayer)
@@ -1822,23 +2453,25 @@
         for display in currentViewModel?.displays ?? [] {
             let groupContainer = CALayer()
             groupContainer.name = display.displayLabel
-            groupContainer.cornerRadius = 16
+            groupContainer.cornerRadius = 14
             groupContainer.masksToBounds = false
-            groupContainer.borderWidth = 1
-            groupContainer.borderColor = NSColor.separatorColor.withAlphaComponent(0.26).cgColor
-            groupContainer.backgroundColor = NSColor.windowBackgroundColor.withAlphaComponent(0.28).cgColor
+            groupContainer.borderWidth = 0
+            groupContainer.borderColor = NSColor.clear.cgColor
+            groupContainer.backgroundColor = NSColor.windowBackgroundColor.cgColor
             groupContainer.shadowColor = NSColor.black.cgColor
             groupContainer.shadowOpacity = 0
             groupContainer.shadowRadius = 0
             groupContainer.shadowOffset = .zero
 
             let segments = display.spaces.map { space in
-                let container = CALayer()
+                let container = CAGradientLayer()
                 container.name = space.label
                 container.cornerRadius = 10
                 container.borderWidth = 1
                 container.borderColor = NSColor.separatorColor.withAlphaComponent(0.34).cgColor
-                container.backgroundColor = spaceColor(for: space).cgColor
+                container.backgroundColor = NSColor.clear.cgColor
+                container.startPoint = CGPoint(x: 0.5, y: 1.0)
+                container.endPoint = CGPoint(x: 0.5, y: 0.0)
                 container.shadowColor = NSColor.black.cgColor
 
                 let labelLayer = makeTextLayer(
@@ -2033,7 +2666,8 @@
     private func layoutSpaceLaneSegments() {
         guard !spaceLaneDisplayGroups.isEmpty, !spaceLaneSegments.isEmpty else { return }
 
-        let groupHeight = max(1, laneLayer.bounds.height - 16)
+        let groupOuterVerticalInset: CGFloat = 6
+        let groupHeight = max(1, laneLayer.bounds.height - groupOuterVerticalInset * 2)
         let segmentHeight = max(1, groupHeight - SpaceLaneMetrics.groupVerticalPadding * 2)
         let groupGapWidth = CGFloat(max(0, spaceLaneDisplayGroups.count - 1)) * SpaceLaneMetrics.groupGap
         let segmentGapWidth = spaceLaneDisplayGroups.reduce(CGFloat(0)) { total, group in
@@ -2076,7 +2710,7 @@
             let groupWidth = groupWidths[index]
             group.containerLayer.frame = CGRect(
                 x: x,
-                y: 8,
+                y: groupOuterVerticalInset,
                 width: groupWidth,
                 height: groupHeight
             )
@@ -2112,46 +2746,35 @@
             segment.space.id == activeSpaceFocusID
                 || appHoverAssociatedSpaceIDs.contains(segment.space.id)
                 || segment.space.id == windowHoverAssociatedSpaceID
+                || segment.space.id == currentViewModel?.lockedSpaceID
         }
         let hasCurrentSegment = group.display.spaces.contains { $0.isCurrent }
-        let hasWindows = group.display.spaces.contains { $0.windowCount > 0 }
-        let background = hasActiveSegment
-            ? accentTintedWindowBackground(fraction: 0.035, alpha: 0.62)
-            : NSColor.windowBackgroundColor.withAlphaComponent(hasWindows ? 0.44 : 0.30)
-
-        group.containerLayer.backgroundColor = background.cgColor
-        group.containerLayer.borderColor = (hasActiveSegment
-            ? spaceLaneOccupiedColor.withAlphaComponent(0.36)
-            : hasCurrentSegment
-                ? NSColor.labelColor.withAlphaComponent(0.22)
-                : NSColor.separatorColor.withAlphaComponent(0.24)
-        ).cgColor
-        group.containerLayer.borderWidth = 1
-        group.containerLayer.shadowOpacity = hasActiveSegment ? 0.12 : 0
-        group.containerLayer.shadowRadius = hasActiveSegment ? 14 : 0
-        group.containerLayer.shadowOffset = CGSize(width: 0, height: -3)
+        group.containerLayer.backgroundColor = NSColor.windowBackgroundColor.cgColor
+        group.containerLayer.borderColor = NSColor.clear.cgColor
+        group.containerLayer.borderWidth = 0
+        group.containerLayer.shadowOpacity = 0
+        group.containerLayer.shadowRadius = 0
+        group.containerLayer.shadowOffset = .zero
         group.containerLayer.zPosition = hasActiveSegment ? 8 : hasCurrentSegment ? 4 : 0
-        group.containerLayer.shadowPath = CGPath(
-            roundedRect: group.containerLayer.bounds,
-            cornerWidth: group.containerLayer.cornerRadius,
-            cornerHeight: group.containerLayer.cornerRadius,
-            transform: nil
-        )
+        group.containerLayer.shadowPath = nil
     }
 
     private func applySpaceLaneVisualState(_ segment: SpaceLaneSegmentLayers) {
         let isHovered = segment.space.id == activeSpaceFocusID
         let isFocused = segment.space.id == activeSpaceFocusID
+        let isLocked = segment.space.id == currentViewModel?.lockedSpaceID
         let isCurrent = segment.space.isCurrent
         let hasWindows = segment.space.windowCount > 0
         let isAppAssociated = appHoverAssociatedSpaceIDs.contains(segment.space.id)
         let isWindowAssociated = segment.space.id == windowHoverAssociatedSpaceID
-        let isActive = isHovered || isFocused
+        let isActive = isHovered || isFocused || isLocked
         let isAssociated = (isAppAssociated || isWindowAssociated) && !isActive
 
-        segment.containerLayer.borderWidth = (hasWindows || isCurrent || isActive || isAssociated) ? 1.5 : 1
+        segment.containerLayer.borderWidth = isLocked
+            ? 6
+            : (hasWindows || isCurrent || isActive || isAssociated) ? 1.5 : 1
         segment.containerLayer.borderColor = (isActive
-            ? spaceLaneOccupiedColor.withAlphaComponent(0.62)
+            ? spaceLaneOccupiedColor.withAlphaComponent(isLocked ? 0.92 : 0.62)
             : isAssociated
                 ? spaceLaneOccupiedColor.withAlphaComponent(0.50)
                 : hasWindows
@@ -2160,28 +2783,49 @@
                     ? NSColor.labelColor.withAlphaComponent(0.34)
                 : NSColor.separatorColor.withAlphaComponent(0.34)
         ).cgColor
-        segment.containerLayer.backgroundColor = (isActive
-            ? accentTintedWindowBackground(fraction: 0.10, alpha: 0.94)
-            : isAssociated
-                ? accentTintedWindowBackground(fraction: 0.07, alpha: 0.90)
-                : spaceColor(for: segment.space)
-        ).cgColor
-        segment.containerLayer.shadowOpacity = isActive ? 0.26 : isAssociated ? 0.18 : isCurrent ? 0.14 : 0
-        segment.containerLayer.shadowRadius = isActive ? 24 : isAssociated ? 18 : isCurrent ? 12 : 0
+        if !hasWindows {
+            applySpaceLaneSolidFill(to: segment.containerLayer, color: .clear)
+        } else if isActive {
+            applySpaceLaneSolidFill(
+                to: segment.containerLayer,
+                color: accentTintedWindowBackground(fraction: 0.10, alpha: 0.94)
+            )
+        } else if isAssociated {
+            applySpaceLaneSolidFill(
+                to: segment.containerLayer,
+                color: accentTintedWindowBackground(fraction: 0.07, alpha: 0.90)
+            )
+        } else if hasWindows {
+            applySpaceLaneGradientFill(
+                to: segment.containerLayer,
+                colors: spaceLaneIdleOccupiedGradientColors()
+            )
+        }
+        segment.containerLayer.shadowColor = isLocked
+            ? NSColor.white.withAlphaComponent(0.98).cgColor
+            : NSColor.black.cgColor
+        segment.containerLayer.shadowOpacity = (hasWindows || isLocked)
+            ? (isLocked ? 0.72 : isActive ? 0.26 : isAssociated ? 0.18 : isCurrent ? 0.14 : 0)
+            : 0
+        segment.containerLayer.shadowRadius = (hasWindows || isLocked)
+            ? (isLocked ? 30 : isActive ? 24 : isAssociated ? 18 : isCurrent ? 12 : 0)
+            : 0
         segment.containerLayer.shadowOffset = CGSize(
             width: 0,
-            height: isActive ? -6 : isAssociated ? -4 : isCurrent ? -2.5 : 0
+            height: (hasWindows || isLocked) ? (isLocked ? 0 : isActive ? -6 : isAssociated ? -4 : isCurrent ? -2.5 : 0) : 0
         )
-        segment.containerLayer.zPosition = isActive ? 30 : isAssociated ? 18 : isCurrent ? 10 : 0
+        segment.containerLayer.zPosition = isLocked ? 42 : isActive ? 30 : isAssociated ? 18 : isCurrent ? 10 : 0
         segment.containerLayer.transform = (isActive || isAssociated)
             ? CATransform3DMakeScale(isActive ? 1.03 : 1.015, isActive ? 1.03 : 1.015, 1)
             : CATransform3DIdentity
-        segment.containerLayer.shadowPath = CGPath(
-            roundedRect: segment.containerLayer.bounds,
-            cornerWidth: segment.containerLayer.cornerRadius,
-            cornerHeight: segment.containerLayer.cornerRadius,
-            transform: nil
-        )
+        segment.containerLayer.shadowPath = hasWindows
+            ? CGPath(
+                roundedRect: segment.containerLayer.bounds,
+                cornerWidth: segment.containerLayer.cornerRadius,
+                cornerHeight: segment.containerLayer.cornerRadius,
+                transform: nil
+            )
+            : nil
     }
 
     private func shouldScrollSpaceLane(for event: NSEvent) -> Bool {
@@ -2567,6 +3211,10 @@
             return "none"
         }
 
+        guard !isHorizontalMasonryMode else {
+            return "visible"
+        }
+
         let visibleMinX = waterfallScrollOffset
         let visibleMaxX = waterfallScrollOffset + waterfallLayer.bounds.width
         if column.containerLayer.frame.maxX < visibleMinX + WaterfallMetrics.gap {
@@ -2649,17 +3297,24 @@
     }
 
     private func layoutWaterfallColumns() {
+        if isHorizontalMasonryMode {
+            layoutHorizontalMasonryWaterfall()
+            return
+        }
+
         guard !waterfallColumns.isEmpty else {
             waterfallContentWidth = waterfallLayer.bounds.width
             waterfallScrollOffset = 0
+            horizontalMasonryContentHeight = waterfallLayer.bounds.height
+            horizontalMasonryScrollOffset = 0
             waterfallContentLayer.frame = waterfallLayer.bounds
             return
         }
 
         let columnWidth = waterfallColumnWidth()
-        let totalWidth = WaterfallMetrics.contentHorizontalPadding * 2
-            + CGFloat(waterfallColumns.count) * columnWidth
+        let columnsWidth = CGFloat(waterfallColumns.count) * columnWidth
             + CGFloat(max(0, waterfallColumns.count - 1)) * WaterfallMetrics.gap
+        let totalWidth = WaterfallMetrics.contentHorizontalPadding * 2 + columnsWidth
         waterfallContentWidth = max(waterfallLayer.bounds.width, totalWidth)
         waterfallScrollOffset = clampedWaterfallAlignmentOffset(waterfallScrollOffset)
         waterfallContentLayer.frame = CGRect(
@@ -2669,7 +3324,7 @@
             height: waterfallLayer.bounds.height
         )
 
-        var x = WaterfallMetrics.contentHorizontalPadding
+        var x = waterfallColumnStartX(columnsWidth: columnsWidth)
         for column in waterfallColumns {
             column.containerLayer.frame = CGRect(
                 x: x,
@@ -2682,7 +3337,215 @@
         }
     }
 
+    private func layoutHorizontalMasonryWaterfall() {
+        guard !waterfallColumns.isEmpty else {
+            waterfallContentWidth = waterfallLayer.bounds.width
+            waterfallScrollOffset = 0
+            horizontalMasonryContentHeight = waterfallLayer.bounds.height
+            horizontalMasonryScrollOffset = 0
+            waterfallContentLayer.frame = waterfallLayer.bounds
+            return
+        }
+
+        let layout = horizontalMasonryLayout()
+        waterfallContentWidth = waterfallLayer.bounds.width
+        waterfallScrollOffset = 0
+        horizontalMasonryContentHeight = layout.contentHeight
+        horizontalMasonryScrollOffset = clampedHorizontalMasonryOffset(horizontalMasonryScrollOffset)
+        waterfallContentLayer.frame = horizontalMasonryContentFrame()
+
+        for column in waterfallColumns {
+            column.containerLayer.frame = CGRect(
+                x: 0,
+                y: 0,
+                width: waterfallContentWidth,
+                height: horizontalMasonryContentHeight
+            )
+            column.containerLayer.masksToBounds = false
+            column.containerLayer.backgroundColor = NSColor.clear.cgColor
+            column.containerLayer.borderColor = NSColor.clear.cgColor
+            column.containerLayer.borderWidth = 0
+            column.containerLayer.shadowOpacity = 0
+            column.containerLayer.shadowRadius = 0
+            column.containerLayer.shadowOffset = .zero
+            column.headerLayer.isHidden = true
+            column.appNameLayer.isHidden = true
+            column.countLayer.isHidden = true
+
+            for card in column.cards {
+                if let frame = layout.cardFramesByWindowID[card.item.window.id] {
+                    card.containerLayer.frame = frame
+                } else {
+                    card.containerLayer.frame = .zero
+                }
+                layoutWaterfallCard(card)
+            }
+        }
+    }
+
+    private struct HorizontalMasonryLayout {
+        let contentHeight: CGFloat
+        let cardFramesByWindowID: [UInt32: CGRect]
+    }
+
+    private func horizontalMasonryLayout() -> HorizontalMasonryLayout {
+        let cards = horizontalMasonryCardsInPlacementOrder()
+        guard !cards.isEmpty else {
+            return HorizontalMasonryLayout(
+                contentHeight: waterfallLayer.bounds.height,
+                cardFramesByWindowID: [:]
+            )
+        }
+
+        let viewportWidth = max(1, waterfallLayer.bounds.width)
+        let availableWidth = max(
+            HorizontalMasonryMetrics.cardMinWidth,
+            viewportWidth - HorizontalMasonryMetrics.horizontalPadding * 2
+        )
+        let maximumLaneCount = max(
+            1,
+            Int(
+                floor(
+                    (availableWidth + HorizontalMasonryMetrics.cardGap)
+                        / (HorizontalMasonryMetrics.cardMinWidth + HorizontalMasonryMetrics.cardGap)
+                )
+            )
+        )
+        let laneCount = min(maximumLaneCount, max(1, cards.count))
+        let fittingWidth = (
+            availableWidth - CGFloat(max(0, laneCount - 1)) * HorizontalMasonryMetrics.cardGap
+        ) / CGFloat(laneCount)
+        let cardWidth = floor(
+            min(
+                HorizontalMasonryMetrics.cardMaxWidth,
+                max(HorizontalMasonryMetrics.cardMinWidth, fittingWidth)
+            )
+        )
+        let usedWidth = CGFloat(laneCount) * cardWidth
+            + CGFloat(max(0, laneCount - 1)) * HorizontalMasonryMetrics.cardGap
+        let startX = max(
+            HorizontalMasonryMetrics.horizontalPadding,
+            (viewportWidth - usedWidth) / 2
+        )
+
+        var laneHeights = Array(repeating: CGFloat(0), count: laneCount)
+        var plannedFrames: [(windowID: UInt32, x: CGFloat, top: CGFloat, width: CGFloat, height: CGFloat)] = []
+
+        for card in cards {
+            let laneIndex = laneHeights.enumerated().min { lhs, rhs in
+                if abs(lhs.element - rhs.element) > 0.5 {
+                    return lhs.element < rhs.element
+                }
+                return lhs.offset < rhs.offset
+            }?.offset ?? 0
+            let cardHeight = horizontalMasonryCardHeight(
+                for: card,
+                width: cardWidth,
+                viewportHeight: waterfallLayer.bounds.height
+            )
+            let x = startX + CGFloat(laneIndex) * (cardWidth + HorizontalMasonryMetrics.cardGap)
+            let top = HorizontalMasonryMetrics.verticalPadding + laneHeights[laneIndex]
+            plannedFrames.append((
+                windowID: card.item.window.id,
+                x: x,
+                top: top,
+                width: cardWidth,
+                height: cardHeight
+            ))
+            laneHeights[laneIndex] += cardHeight + HorizontalMasonryMetrics.cardGap
+        }
+
+        let tallestLane = laneHeights.max().map {
+            max(0, $0 - HorizontalMasonryMetrics.cardGap)
+        } ?? 0
+        let contentHeight = max(
+            waterfallLayer.bounds.height,
+            HorizontalMasonryMetrics.verticalPadding * 2 + tallestLane
+        )
+        let frames = Dictionary(
+            uniqueKeysWithValues: plannedFrames.map { planned in
+                (
+                    planned.windowID,
+                    CGRect(
+                        x: planned.x,
+                        y: contentHeight - planned.top - planned.height,
+                        width: planned.width,
+                        height: planned.height
+                    )
+                )
+            }
+        )
+
+        return HorizontalMasonryLayout(contentHeight: contentHeight, cardFramesByWindowID: frames)
+    }
+
+    private func horizontalMasonryCardHeight(
+        for card: WaterfallCardLayers,
+        width: CGFloat,
+        viewportHeight: CGFloat
+    ) -> CGFloat {
+        let thumbnailHeight = min(
+            max(
+                HorizontalMasonryMetrics.minThumbnailHeight,
+                width / horizontalMasonryThumbnailAspectRatio(for: card)
+            ),
+            max(1, viewportHeight * HorizontalMasonryMetrics.maxThumbnailHeightFraction)
+        )
+        return HorizontalMasonryMetrics.titleBarHeight
+            + HorizontalMasonryMetrics.titleGap
+            + thumbnailHeight
+    }
+
+    private func horizontalMasonryThumbnailAspectRatio(for card: WaterfallCardLayers) -> CGFloat {
+        if card.item.window.isFullscreen {
+            return 16.0 / 9.0
+        }
+        if card.item.window.isMinimized {
+            return 4.0 / 3.0
+        }
+
+        switch Int(card.item.window.id % 4) {
+        case 0:
+            return 16.0 / 9.0
+        case 1:
+            return 3.0 / 2.0
+        case 2:
+            return 4.0 / 3.0
+        default:
+            return 5.0 / 4.0
+        }
+    }
+
+    private func horizontalMasonryContentFrame() -> CGRect {
+        let contentHeight = max(waterfallLayer.bounds.height, horizontalMasonryContentHeight)
+        return CGRect(
+            x: 0,
+            y: waterfallLayer.bounds.height - contentHeight + horizontalMasonryScrollOffset,
+            width: waterfallLayer.bounds.width,
+            height: contentHeight
+        )
+    }
+
+    private func waterfallColumnStartX(columnsWidth: CGFloat) -> CGFloat {
+        guard currentViewModel?.lockedSpaceID != nil else {
+            return WaterfallMetrics.contentHorizontalPadding
+        }
+
+        let centeredStart = (waterfallContentWidth - columnsWidth) / 2
+        return max(WaterfallMetrics.contentHorizontalPadding, centeredStart)
+    }
+
     private func layoutWaterfallColumn(_ column: WaterfallColumnLayers) {
+        column.containerLayer.cornerRadius = 14
+        column.containerLayer.masksToBounds = true
+        column.containerLayer.backgroundColor = NSColor.controlBackgroundColor.withAlphaComponent(0.56).cgColor
+        column.containerLayer.shadowOpacity = 0
+        column.containerLayer.shadowRadius = 0
+        column.containerLayer.shadowOffset = .zero
+        column.headerLayer.isHidden = false
+        column.appNameLayer.isHidden = false
+        column.countLayer.isHidden = false
+
         let bounds = column.containerLayer.bounds
         let isSpaceFocused = spaceFocusWindowCount(for: column.column.appGroupIndex) > 0
         let isHovered = column.column.appGroupIndex == effectiveHoveredAppGroupIndex
@@ -3403,15 +4266,30 @@
         )
     }
 
+    private var isHorizontalMasonryMode: Bool {
+        waterfallViewMode == .horizontalMasonry
+    }
+
     private var waterfallMaxScrollOffset: CGFloat {
-        max(0, waterfallContentWidth - waterfallLayer.bounds.width)
+        guard !isHorizontalMasonryMode else { return 0 }
+        return max(0, waterfallContentWidth - waterfallLayer.bounds.width)
     }
 
     private func clampedWaterfallOffset(_ offset: CGFloat) -> CGFloat {
         min(max(0, offset), waterfallMaxScrollOffset)
     }
 
+    private var horizontalMasonryMaxScrollOffset: CGFloat {
+        max(0, horizontalMasonryContentHeight - waterfallLayer.bounds.height)
+    }
+
+    private func clampedHorizontalMasonryOffset(_ offset: CGFloat) -> CGFloat {
+        min(max(0, offset), horizontalMasonryMaxScrollOffset)
+    }
+
     private func waterfallMaxVerticalScrollOffset(for appGroupIndex: Int) -> CGFloat {
+        guard !isHorizontalMasonryMode else { return 0 }
+
         guard
             let column = waterfallColumns.first(where: { $0.column.appGroupIndex == appGroupIndex })
         else {
@@ -3452,20 +4330,43 @@
         return states.joined(separator: " / ")
     }
 
-    private func spaceColor(for space: QuickSwitchSpaceViewModel) -> NSColor {
-        if space.windowCount > 0 {
-            return NSColor.controlBackgroundColor.withAlphaComponent(0.36)
-        }
-
-        return NSColor.labelColor.withAlphaComponent(space.isCurrent ? 0.07 : 0.05)
-    }
-
     private var spaceLaneOccupiedColor: NSColor {
         if effectiveAppearance.bestMatch(from: [.darkAqua, .aqua]) == .darkAqua {
             return NSColor(calibratedRed: 10 / 255, green: 132 / 255, blue: 1, alpha: 1)
         }
 
         return NSColor(calibratedRed: 0, green: 122 / 255, blue: 1, alpha: 1)
+    }
+
+    private func spaceLaneIdleOccupiedGradientColors() -> [NSColor] {
+        if effectiveAppearance.bestMatch(from: [.darkAqua, .aqua]) == .darkAqua {
+            let blue = NSColor(calibratedRed: 36 / 255, green: 54 / 255, blue: 72 / 255, alpha: 1)
+            let surface = NSColor.windowBackgroundColor.withAlphaComponent(1)
+            return [blue, surface]
+        }
+
+        return [
+            NSColor(calibratedRed: 232 / 255, green: 246 / 255, blue: 1, alpha: 1),
+            NSColor.white
+        ]
+    }
+
+    private func applySpaceLaneGradientFill(to layer: CALayer, colors: [NSColor]) {
+        if let gradientLayer = layer as? CAGradientLayer {
+            gradientLayer.colors = colors.map(\.cgColor)
+            gradientLayer.locations = [0, 1]
+            gradientLayer.startPoint = CGPoint(x: 0.5, y: 1.0)
+            gradientLayer.endPoint = CGPoint(x: 0.5, y: 0.0)
+        }
+        layer.backgroundColor = NSColor.clear.cgColor
+    }
+
+    private func applySpaceLaneSolidFill(to layer: CALayer, color: NSColor) {
+        if let gradientLayer = layer as? CAGradientLayer {
+            gradientLayer.colors = nil
+            gradientLayer.locations = nil
+        }
+        layer.backgroundColor = color.cgColor
     }
 
     private func makeFullscreenMarkerLayer(for space: QuickSwitchSpaceViewModel) -> CALayer? {
@@ -3687,11 +4588,18 @@
     }
 
     private func fullscreenMarkerFrame(in segmentBounds: CGRect) -> CGRect {
-        CGRect(
+        let topReserved: CGFloat = 32
+        let bottomReserved: CGFloat = 16
+        let availableHeight = max(20, segmentBounds.height - topReserved - bottomReserved)
+        let markerHeight = min(30, max(20, availableHeight))
+        let markerCenterY = bottomReserved + availableHeight * 0.5
+        let markerY = max(8, min(segmentBounds.height - topReserved - markerHeight, markerCenterY - markerHeight * 0.5))
+
+        return CGRect(
             x: 10,
-            y: 12,
+            y: markerY,
             width: max(1, segmentBounds.width - 20),
-            height: max(1, segmentBounds.height - 64)
+            height: markerHeight
         )
     }
 
@@ -3778,6 +4686,13 @@
             let visibleFrame = column.containerLayer.frame.offsetBy(dx: waterfallContentLayer.frame.minX, dy: 0)
             let appGroupIndex = column.column.appGroupIndex
             let isHovered = appGroupIndex == effectiveHoveredAppGroupIndex
+            let firstCardFrame = column.cards.first?.containerLayer.frame
+            let headerToFirstCardGap = firstCardFrame.map {
+                column.headerLayer.frame.minY - $0.maxY
+            }
+            let topToFirstCardGap = firstCardFrame.map {
+                column.containerLayer.bounds.height - $0.maxY
+            }
 
             return [
                 "appGroupIndex": appGroupIndex,
@@ -3791,6 +4706,9 @@
                 "spaceFocusDirection": spaceFocusDirection(for: appGroupIndex),
                 "frame": dictionary(from: column.containerLayer.frame),
                 "visibleFrame": dictionary(from: visibleFrame),
+                "headerFrame": dictionary(from: column.headerLayer.frame),
+                "headerToFirstCardGap": headerToFirstCardGap.map(Double.init) ?? NSNull(),
+                "topToFirstCardGap": topToFirstCardGap.map(Double.init) ?? NSNull(),
                 "appNameFrame": dictionary(from: column.appNameLayer.frame),
                 "appNameAlignment": column.appNameLayer.alignmentMode.rawValue,
                 "appNameColor": colorDictionary(from: column.appNameLayer.foregroundColor),
@@ -4031,6 +4949,8 @@
                 "shadowOpacity": Double(group.containerLayer.shadowOpacity),
                 "shadowRadius": Double(group.containerLayer.shadowRadius),
                 "groupGap": Double(SpaceLaneMetrics.groupGap),
+                "groupHorizontalPadding": Double(SpaceLaneMetrics.groupHorizontalPadding),
+                "groupVerticalPadding": Double(SpaceLaneMetrics.groupVerticalPadding),
                 "segmentGap": Double(SpaceLaneMetrics.segmentGap)
             ] as [String: Any]
         }
@@ -4049,6 +4969,10 @@
                     dx: (group?.containerLayer.frame.minX ?? 0) + spaceLaneContentLayer.frame.minX,
                     dy: group?.containerLayer.frame.minY ?? 0
                 )
+                let fullscreenMarkerFrame = segment.fullscreenMarkerLayer?.frame
+                let fullscreenMarkerCenterRatio = fullscreenMarkerFrame.map {
+                    Double($0.midY / max(1, segment.containerLayer.bounds.height))
+                }
                 return [
                     "displayUUID": display.displayUUID,
                     "displayLabel": display.displayLabel,
@@ -4058,15 +4982,23 @@
                     "visualStates": visualStates(for: space),
                     "fullscreenMarkerVisible": segment.fullscreenMarkerLayer != nil,
                     "fullscreenMarkerKind": segment.fullscreenMarkerLayer == nil ? "none" : "cornerBracket",
-                    "fullscreenMarkerFrame": segment.fullscreenMarkerLayer.map { dictionary(from: $0.frame) } ?? NSNull(),
+                    "fullscreenMarkerFrame": fullscreenMarkerFrame.map { dictionary(from: $0) } ?? NSNull(),
+                    "fullscreenMarkerCenterRatio": fullscreenMarkerCenterRatio ?? NSNull(),
                     "windowBlockCount": segment.windowBlocks.count,
                     "windowBlockColors": segment.windowBlocks.map { colorDictionary(from: $0.backgroundColor) },
                     "windowBlockFrames": segment.windowBlocks.map { dictionary(from: $0.frame) },
+                    "backgroundKind": spaceLaneFillKind(for: segment.containerLayer),
                     "backgroundColor": colorDictionary(from: segment.containerLayer.backgroundColor),
+                    "gradientColors": gradientColorDictionaries(from: segment.containerLayer),
                     "borderColor": colorDictionary(from: segment.containerLayer.borderColor),
                     "borderWidth": Double(segment.containerLayer.borderWidth),
+                    "shadowColor": colorDictionary(from: segment.containerLayer.shadowColor),
                     "shadowOpacity": Double(segment.containerLayer.shadowOpacity),
                     "shadowRadius": Double(segment.containerLayer.shadowRadius),
+                    "shadowOffset": [
+                        "width": Double(segment.containerLayer.shadowOffset.width),
+                        "height": Double(segment.containerLayer.shadowOffset.height)
+                    ],
                     "appFrame": dictionary(from: segment.appLayer.frame),
                     "frame": dictionary(from: segment.containerLayer.frame),
                     "visibleFrame": dictionary(from: visibleFrame),
@@ -4105,6 +5037,9 @@
         }
         if space.id == activeSpaceFocusID {
             states.append("focused")
+        }
+        if space.id == currentViewModel?.lockedSpaceID {
+            states.append("locked")
         }
         if space.type == .fullscreen {
             states.append("fullscreen")
@@ -4153,4 +5088,23 @@
             "alpha": Double(nsColor.alphaComponent)
         ]
     }
+
+    private func gradientColorDictionaries(from layer: CALayer) -> [[String: Double]] {
+        guard let gradientLayer = layer as? CAGradientLayer else { return [] }
+        return (gradientLayer.colors ?? []).map { color in
+            let cgColor = color as! CGColor
+            return colorDictionary(from: cgColor)
+        }
+    }
+
+    private func spaceLaneFillKind(for layer: CALayer) -> String {
+        if !gradientColorDictionaries(from: layer).isEmpty {
+            return "gradient"
+        }
+        let background = colorDictionary(from: layer.backgroundColor)
+        if background["alpha", default: 0] <= 0.01 {
+            return "clear"
+        }
+        return "solid"
+    }
 }

--
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