feat: improve drag-and-drop over alttab (closes #5350)

src/logic/events/CursorEvents.swift

@@ -115,13 +115,17 @@ class CursorEvents {
     }
 
     private static func handleMouseMoved(_ cgEvent: CGEvent) -> Unmanaged<CGEvent>? {
-        updateDeadzoneSituation(cgEvent)
+        if isAllowedToReactToPointerMovement(cgEvent.location) {
-        if isAllowedToMouseHover {
             TilesView.thumbnailOverView.updateHover()
         }
         return Unmanaged.passUnretained(cgEvent)
     }
 
+    static func isAllowedToReactToPointerMovement(_ location: CGPoint) -> Bool {
+        updateDeadzoneSituation(location)
+        return isAllowedToMouseHover
+    }
+
     private static func pointerLocationInWindow() -> NSPoint {
         TilesPanel.shared.mouseLocationOutsideOfEventStream
     }
@@ -158,8 +162,7 @@ class CursorEvents {
 
     /// when using the trackpad, the user may swipe with a slight mistake. This will create a small cursor movement
     /// we ignore those, as they are not intended. Intended movements will be larger and not ignored
-    private static func updateDeadzoneSituation(_ cgEvent: CGEvent) {
+    private static func updateDeadzoneSituation(_ location: CGPoint) {
-        let location = cgEvent.location
         guard let deadZoneInitialPosition else {
             deadZoneInitialPosition = location
             isAllowedToMouseHover = false

src/ui/main-window/TileView.swift

@@ -17,9 +17,7 @@ class TileView: FlippedView {
 
     var mouseUpCallback: (() -> Void)!
     var mouseMovedCallback: (() -> Void)!
-    var dragAndDropTimer: Timer?
     var indexInRecycledViews: Int!
-    private var lastDragLocation: NSPoint?
 
     var isFirstInRow = false
     var isLastInRow = false
@@ -32,57 +30,6 @@ class TileView: FlippedView {
 
     override func isAccessibilityElement() -> Bool { true }
 
-    override func wantsPeriodicDraggingUpdates() -> Bool { false }
-
-    override func draggingUpdated(_ sender: NSDraggingInfo) -> NSDragOperation {
-        let location = sender.draggingLocation
-        if location != lastDragLocation {
-            lastDragLocation = location
-            mouseMovedCallback()
-        }
-        return .link
-    }
-
-    override func draggingEntered(_ sender: NSDraggingInfo) -> NSDragOperation {
-        lastDragLocation = sender.draggingLocation
-        mouseMovedCallback()
-        setDraggingTimer()
-        return .link
-    }
-
-    private func setDraggingTimer() {
-        dragAndDropTimer?.invalidate()
-        dragAndDropTimer = Timer(timeInterval: 2, repeats: false, block: { [weak self] _ in
-            guard let self else { return }
-            // the user can tab to focus the next thumbnail, while still dragging. We don't want to perform drag then
-            if Windows.selectedWindowIndex == Windows.hoveredWindowIndex {
-                self.mouseUpCallback()
-            }
-        })
-        dragAndDropTimer?.tolerance = 0.2
-        if let dragAndDropTimer {
-            // we need to target .common since dragging is running in .eventTracking on trackpad
-            RunLoop.main.add(dragAndDropTimer, forMode: .common)
-        }
-    }
-
-    override func draggingExited(_ sender: NSDraggingInfo?) {
-        lastDragLocation = nil
-        dragAndDropTimer?.invalidate()
-        dragAndDropTimer = nil
-        TilesView.thumbnailOverView.resetHoveredWindow()
-    }
-
-    override func performDragOperation(_ sender: NSDraggingInfo) -> Bool {
-        dragAndDropTimer?.invalidate()
-        dragAndDropTimer = nil
-        let urls = sender.draggingPasteboard.readObjects(forClasses: [NSURL.self]) as! [URL]
-        let appUrl = window_!.application.bundleURL!
-        let open = try? NSWorkspace.shared.open(urls, withApplicationAt: appUrl, options: [], configuration: [:])
-        App.hideUi()
-        return open != nil
-    }
-
     func mouseMoved() {
         updateLabelTooltipIfNeeded()
         mouseMovedCallback()
@@ -96,7 +43,6 @@ class TileView: FlippedView {
     convenience init() {
         self.init(frame: .zero)
         setupView()
-        observeDragAndDrop()
     }
 
     /// The frame used by TileUnderLayer to position the highlight rectangle.
@@ -569,11 +515,6 @@ class TileView: FlippedView {
         return "Red badge"
     }
 
-    private func observeDragAndDrop() {
-        // we only handle URLs (i.e. not text, image, or other draggable things)
-        registerForDraggedTypes([NSPasteboard.PasteboardType(kUTTypeURL as String)])
-    }
-
     static func makeShadow(_ color: NSColor?) -> NSShadow? {
         let shadow = NSShadow()
         shadow.shadowColor = color

src/ui/main-window/TilesView.swift

@@ -644,7 +644,7 @@ class ScrollView: NSScrollView {
 
     convenience init() {
         self.init(frame: .zero)
-        documentView = FlippedView(frame: .zero)
+        documentView = TilesDocumentView(frame: .zero)
         documentView!.wantsLayer = true
         drawsBackground = false
         hasVerticalScroller = true
@@ -678,6 +678,107 @@ class ScrollView: NSScrollView {
     }
 }
 
+class TilesDocumentView: FlippedView {
+    private static let dragAndDropTimerDelay = TimeInterval(2)
+    private static let dragAndDropTimerResetDistance = CGFloat(5)
+
+    private weak var dragTarget: TileView?
+    private var lastDragLocation: NSPoint?
+    private var timerResetLocation: NSPoint?
+    private var dragAndDropTimer: Timer?
+
+    override func wantsPeriodicDraggingUpdates() -> Bool { false }
+
+    override init(frame frameRect: NSRect) {
+        super.init(frame: frameRect)
+        // we only handle URLs (i.e. not text, image, or other draggable things)
+        registerForDraggedTypes([NSPasteboard.PasteboardType(kUTTypeURL as String)])
+    }
+
+    required init?(coder: NSCoder) {
+        fatalError("Class only supports programmatic initialization")
+    }
+
+    override func draggingEntered(_ sender: NSDraggingInfo) -> NSDragOperation {
+        let location = sender.draggingLocation
+        lastDragLocation = location
+        return dragOperation(location)
+    }
+
+    override func draggingUpdated(_ sender: NSDraggingInfo) -> NSDragOperation {
+        let location = sender.draggingLocation
+        if location != lastDragLocation { lastDragLocation = location }
+        return dragOperation(location)
+    }
+
+    override func draggingExited(_ sender: NSDraggingInfo?) {
+        resetDraggingState(true)
+    }
+
+    override func performDragOperation(_ sender: NSDraggingInfo) -> Bool {
+        defer { resetDraggingState(false) }
+        guard let target = targetView(sender.draggingLocation) ?? dragTarget,
+              let window = target.window_,
+              let appUrl = window.application.bundleURL else { return false }
+        guard let urls = sender.draggingPasteboard.readObjects(forClasses: [NSURL.self]) as? [URL],
+              !urls.isEmpty else { return false }
+        let open = try? NSWorkspace.shared.open(urls, withApplicationAt: appUrl, options: [], configuration: [:])
+        if open != nil { App.hideUi() }
+        return open != nil
+    }
+
+    override func concludeDragOperation(_ sender: NSDraggingInfo?) {
+        resetDraggingState(false)
+    }
+
+    private func dragOperation(_ location: NSPoint) -> NSDragOperation {
+        guard let target = targetView(location) else {
+            resetDraggingState(true)
+            return []
+        }
+        if dragTarget !== target {
+            dragTarget = target
+            restartDraggingTimer(location)
+        } else if shouldRestartDraggingTimer(location) {
+            restartDraggingTimer(location)
+        }
+        if let window, CursorEvents.isAllowedToReactToPointerMovement(window.convertPoint(toScreen: location)) {
+            target.mouseMovedCallback()
+        }
+        return .link
+    }
+
+    private func shouldRestartDraggingTimer(_ location: NSPoint) -> Bool {
+        guard let timerResetLocation else { return true }
+        return hypot(location.x - timerResetLocation.x, location.y - timerResetLocation.y) >= Self.dragAndDropTimerResetDistance
+    }
+
+    private func restartDraggingTimer(_ location: NSPoint) {
+        timerResetLocation = location
+        dragAndDropTimer?.invalidate()
+        dragAndDropTimer = Timer(timeInterval: Self.dragAndDropTimerDelay, repeats: false, block: { [weak self] _ in
+            guard let self, let dragTarget = self.dragTarget else { return }
+            dragTarget.mouseUpCallback()
+        })
+        dragAndDropTimer?.tolerance = 0.2
+        if let dragAndDropTimer { RunLoop.main.add(dragAndDropTimer, forMode: .common) }
+    }
+
+    private func resetDraggingState(_ resetHoveredWindow: Bool) {
+        lastDragLocation = nil
+        dragTarget = nil
+        timerResetLocation = nil
+        dragAndDropTimer?.invalidate()
+        dragAndDropTimer = nil
+        if resetHoveredWindow { TilesView.thumbnailOverView.resetHoveredWindow() }
+    }
+
+    private func targetView(_ location: NSPoint) -> TileView? {
+        let overlay = TilesView.thumbnailOverView
+        return overlay.findTarget(overlay.convert(location, from: nil))
+    }
+}
+
 class FlippedView: NSView {
     override var isFlipped: Bool { true }
     // Prevent AppKit from recursively marking all NSControl subviews as needsDisplay during makeKeyAndOrderFront