Dismiss file-drop hints when the drag interaction ends

Sources/FileDropHintPresentation.swift

@@ -0,0 +1,118 @@
+import AppKit
+import CmuxFoundation
+
+/// Owns only drag feedback. Dismissing a hint must not cancel WebKit's drop delivery.
+@MainActor
+final class FileDropHintPresentation: NSObject {
+    private enum Phase: Equatable {
+        case idle
+        case tracking(Int)
+        case dismissed(Int)
+    }
+
+    let badge = FileDropHintBadgeView(frame: .zero)
+    private weak var hostWindow: NSWindow?
+    private var phase = Phase.idle
+    private var eventMonitor: Any?
+    private let displayDuration: Duration
+    private var deadline: MainActorCoalescingDeadlineTimer<FileDropHintPresentation>?
+
+    init(displayDuration: Duration = .seconds(8)) {
+        self.displayDuration = displayDuration
+        super.init()
+    }
+
+    deinit {
+        if let eventMonitor { NSEvent.removeMonitor(eventMonitor) }
+        NotificationCenter.default.removeObserver(self)
+    }
+
+    func setHostWindow(_ window: NSWindow?) {
+        guard hostWindow !== window else { return }
+        dismiss()
+        let center = NotificationCenter.default
+        center.removeObserver(self)
+        hostWindow = window
+        guard let window else { return }
+
+        // AppKit delivers these lifecycle notifications synchronously on the main thread.
+        for name in [NSWindow.didResignKeyNotification, NSWindow.willCloseNotification] {
+            center.addObserver(self, selector: #selector(environmentDidChange(_:)), name: name, object: window)
+        }
+        for name in [NSWindow.didBecomeKeyNotification, NSApplication.didResignActiveNotification] {
+            center.addObserver(self, selector: #selector(environmentDidChange(_:)), name: name, object: nil)
+        }
+    }
+
+    func begin(sequenceNumber: Int) {
+        if phase == .tracking(sequenceNumber) || phase == .dismissed(sequenceNumber) {
+            // AppKit may re-enter a destination after focus changes during the same drag.
+            // Its feedback stays dismissed until a genuinely new native session arrives.
+            return
+        }
+        dismiss()
+        phase = .tracking(sequenceNumber)
+    }
+
+    func show(sequenceNumber: Int, text: String, centeredIn target: CGRect, clippedTo bounds: CGRect) {
+        guard case .tracking(let current) = phase, current == sequenceNumber, hostWindow != nil else { return }
+        badge.show(text: text, centeredIn: target, clippedTo: bounds)
+        if deadline == nil {
+            // A genuine display deadline driven by synchronous AppKit callbacks, not a retry.
+            deadline = MainActorCoalescingDeadlineTimer(owner: self) { $0.dismiss() }
+        }
+        if deadline?.isScheduled == false {
+            deadline?.schedule(after: displayDuration)
+        }
+        installEventMonitorIfNeeded()
+    }
+
+    func hideBadge() {
+        badge.hideImmediately()
+    }
+
+    func dismiss() {
+        if case .tracking(let sequenceNumber) = phase {
+            phase = .dismissed(sequenceNumber)
+        }
+        deadline?.cancel()
+        badge.hideImmediately()
+        if let eventMonitor {
+            NSEvent.removeMonitor(eventMonitor)
+            self.eventMonitor = nil
+        }
+    }
+
+    /// Preserve the native end/cancel event so AppKit can also remove the source drag image.
+    func handleEvent(_ event: NSEvent) -> NSEvent {
+        switch event.type {
+        case .leftMouseUp, .rightMouseUp, .otherMouseUp,
+             .leftMouseDown, .rightMouseDown, .otherMouseDown, .mouseMoved, .keyDown:
+            dismiss()
+        case .flagsChanged:
+            hideBadge()
+        default:
+            break
+        }
+        return event
+    }
+
+    private func installEventMonitorIfNeeded() {
+        guard eventMonitor == nil else { return }
+        eventMonitor = NSEvent.addLocalMonitorForEvents(
+            matching: [.leftMouseUp, .rightMouseUp, .otherMouseUp,
+                       .leftMouseDown, .rightMouseDown, .otherMouseDown,
+                       .mouseMoved, .keyDown, .flagsChanged]
+        ) { [weak self] event in
+            self?.handleEvent(event) ?? event
+        }
+    }
+
+    @objc private func environmentDidChange(_ notification: Notification) {
+        if notification.name == NSWindow.didBecomeKeyNotification,
+           notification.object as? NSWindow === hostWindow {
+            return
+        }
+        dismiss()
+    }
+}

Sources/FileDropOverlayView.swift

@@ -3,34 +3,6 @@ import Bonsplit
 import Foundation
 import WebKit
 
-@MainActor
-protocol FileDropPaneTarget: AnyObject {
-    func fileDropDraggingEntered(_ sender: any NSDraggingInfo) -> NSDragOperation
-    func fileDropDraggingUpdated(_ sender: any NSDraggingInfo) -> NSDragOperation
-    func fileDropDraggingExited(_ sender: (any NSDraggingInfo)?)
-    func fileDropPrepareForDragOperation(_ sender: any NSDraggingInfo) -> Bool
-    func fileDropPerformDragOperation(_ sender: any NSDraggingInfo) -> Bool
-    func fileDropConcludeDragOperation(_ sender: (any NSDraggingInfo)?)
-}
-
-extension PaneDropTargetView: FileDropPaneTarget {
-    func fileDropDraggingEntered(_ sender: any NSDraggingInfo) -> NSDragOperation { draggingEntered(sender) }
-    func fileDropDraggingUpdated(_ sender: any NSDraggingInfo) -> NSDragOperation { draggingUpdated(sender) }
-    func fileDropDraggingExited(_ sender: (any NSDraggingInfo)?) { draggingExited(sender) }
-    func fileDropPrepareForDragOperation(_ sender: any NSDraggingInfo) -> Bool { prepareForDragOperation(sender) }
-    func fileDropPerformDragOperation(_ sender: any NSDraggingInfo) -> Bool { performDragOperation(sender) }
-    func fileDropConcludeDragOperation(_ sender: (any NSDraggingInfo)?) { concludeDragOperation(sender) }
-}
-
-extension BrowserPaneDropTargetView: FileDropPaneTarget {
-    func fileDropDraggingEntered(_ sender: any NSDraggingInfo) -> NSDragOperation { draggingEntered(sender) }
-    func fileDropDraggingUpdated(_ sender: any NSDraggingInfo) -> NSDragOperation { draggingUpdated(sender) }
-    func fileDropDraggingExited(_ sender: (any NSDraggingInfo)?) { draggingExited(sender) }
-    func fileDropPrepareForDragOperation(_ sender: any NSDraggingInfo) -> Bool { prepareForDragOperation(sender) }
-    func fileDropPerformDragOperation(_ sender: any NSDraggingInfo) -> Bool { performDragOperation(sender) }
-    func fileDropConcludeDragOperation(_ sender: (any NSDraggingInfo)?) { concludeDragOperation(sender) }
-}
-
 /// Transparent NSView installed on the window's theme frame (above the NSHostingView) to
 /// handle file/URL drags from Finder. Nested NSHostingController layers (created by bonsplit's
 /// SinglePaneWrapper) prevent AppKit's NSDraggingDestination routing from reaching deeply
@@ -61,7 +33,8 @@ final class FileDropOverlayView: NSView {
     var didPerformDragAsText = false
     weak var performedTextDragWebView: WKWebView?
     weak var performedTextPaneDropTarget: (any FileDropPaneTarget)?
-    let hintBadgeView = FileDropHintBadgeView(frame: .zero)
+    let hintPresentation = FileDropHintPresentation()
+    var hintBadgeView: FileDropHintBadgeView { hintPresentation.badge }
     var lastHitTestLogSignature: String?
     var lastDragRouteLogSignatureByPhase: [String: String] = [:]
     weak var hitTestReferenceView: NSView?
@@ -275,6 +248,7 @@ final class FileDropOverlayView: NSView {
 
     override func viewDidMoveToWindow() {
         super.viewDidMoveToWindow()
+        hintPresentation.setHostWindow(window)
         if window == nil {
             clearForwardedMouseDragState(reason: "overlayDetached")
         }
@@ -299,6 +273,7 @@ final class FileDropOverlayView: NSView {
     // HTML5 drag events (dragenter, dragleave, drop) fire correctly.
 
     override func draggingEntered(_ sender: any NSDraggingInfo) -> NSDragOperation {
+        hintPresentation.begin(sequenceNumber: sender.draggingSequenceNumber)
         return updateDragTarget(sender, phase: "entered")
     }
 
@@ -307,7 +282,7 @@ final class FileDropOverlayView: NSView {
     }
 
     override func draggingExited(_ sender: (any NSDraggingInfo)?) {
-        hintBadgeView.hide()
+        hintPresentation.dismiss()
         preparedDragWebView = nil
         preparedPaneDropTarget = nil
         didPerformDragAsText = false
@@ -316,6 +291,10 @@ final class FileDropOverlayView: NSView {
         exitActiveDragTargets(sender)
     }
 
+    override func draggingEnded(_ sender: any NSDraggingInfo) {
+        draggingExited(sender)
+    }
+
     private func exitActiveDragTargets(_ sender: (any NSDraggingInfo)?) {
         if let prev = activeDragWebView {
             prev.draggingExited(sender)
@@ -352,6 +331,7 @@ final class FileDropOverlayView: NSView {
     }
 
     override func prepareForDragOperation(_ sender: any NSDraggingInfo) -> Bool {
+        hintPresentation.dismiss()
         let hasLocalDraggingSource = sender.draggingSource != nil
         let types = sender.draggingPasteboard.types
         let shouldCapture = DragOverlayRoutingPolicy.shouldCaptureFileDropDestination(
@@ -414,14 +394,14 @@ final class FileDropOverlayView: NSView {
     }
 
     override func performDragOperation(_ sender: any NSDraggingInfo) -> Bool {
+        hintPresentation.dismiss()
         let hasLocalDraggingSource = sender.draggingSource != nil
         let types = sender.draggingPasteboard.types
         let shouldCapture = DragOverlayRoutingPolicy.shouldCaptureFileDropDestination(
             pasteboardTypes: types,
             hasLocalDraggingSource: hasLocalDraggingSource
         )
         if shouldRouteFileDropToTextDestination(sender) {
-            hintBadgeView.hide()
             didPerformDragAsText = false
             performedTextDragWebView = nil
             performedTextPaneDropTarget = nil
@@ -515,7 +495,7 @@ final class FileDropOverlayView: NSView {
 
     override func concludeDragOperation(_ sender: (any NSDraggingInfo)?) {
         defer {
-            hintBadgeView.hide()
+            hintPresentation.dismiss()
             preparedDragWebView = nil
             activeDragWebView = nil
             preparedPaneDropTarget = nil

Sources/FileDropOverlayViewHitTesting.swift

@@ -131,10 +131,15 @@ extension FileDropOverlayView {
                   !DragOverlayRoutingPolicy.currentModifierFlags.contains(.shift),
                   let hintText = FileDropTextDestinationKind.editor.hintText(for: .preview),
                   let targetBounds = hintBadgeTargetBoundsUnderPoint(windowPoint) else {
-                hintBadgeView.hide()
+                hintPresentation.hideBadge()
                 return
             }
-            hintBadgeView.show(text: hintText, centeredIn: targetBounds, clippedTo: bounds)
+            hintPresentation.show(
+                sequenceNumber: sender.draggingSequenceNumber,
+                text: hintText,
+                centeredIn: targetBounds,
+                clippedTo: bounds
+            )
             return
         }
 
@@ -146,10 +151,15 @@ extension FileDropOverlayView {
         ), let kind,
            let hintText = kind.hintText(for: alternateBehavior),
            let targetBounds = hintBadgeTargetBoundsUnderPoint(windowPoint) else {
-            hintBadgeView.hide()
+            hintPresentation.hideBadge()
             return
         }
-        hintBadgeView.show(text: hintText, centeredIn: targetBounds, clippedTo: bounds)
+        hintPresentation.show(
+            sequenceNumber: sender.draggingSequenceNumber,
+            text: hintText,
+            centeredIn: targetBounds,
+            clippedTo: bounds
+        )
     }
 
     func textDropDestinationKindUnderPoint(_ windowPoint: NSPoint) -> FileDropTextDestinationKind? {

Sources/FileDropPaneTarget.swift

@@ -0,0 +1,29 @@
+import AppKit
+
+@MainActor
+protocol FileDropPaneTarget: AnyObject {
+    func fileDropDraggingEntered(_ sender: any NSDraggingInfo) -> NSDragOperation
+    func fileDropDraggingUpdated(_ sender: any NSDraggingInfo) -> NSDragOperation
+    func fileDropDraggingExited(_ sender: (any NSDraggingInfo)?)
+    func fileDropPrepareForDragOperation(_ sender: any NSDraggingInfo) -> Bool
+    func fileDropPerformDragOperation(_ sender: any NSDraggingInfo) -> Bool
+    func fileDropConcludeDragOperation(_ sender: (any NSDraggingInfo)?)
+}
+
+extension PaneDropTargetView: FileDropPaneTarget {
+    func fileDropDraggingEntered(_ sender: any NSDraggingInfo) -> NSDragOperation { draggingEntered(sender) }
+    func fileDropDraggingUpdated(_ sender: any NSDraggingInfo) -> NSDragOperation { draggingUpdated(sender) }
+    func fileDropDraggingExited(_ sender: (any NSDraggingInfo)?) { draggingExited(sender) }
+    func fileDropPrepareForDragOperation(_ sender: any NSDraggingInfo) -> Bool { prepareForDragOperation(sender) }
+    func fileDropPerformDragOperation(_ sender: any NSDraggingInfo) -> Bool { performDragOperation(sender) }
+    func fileDropConcludeDragOperation(_ sender: (any NSDraggingInfo)?) { concludeDragOperation(sender) }
+}
+
+extension BrowserPaneDropTargetView: FileDropPaneTarget {
+    func fileDropDraggingEntered(_ sender: any NSDraggingInfo) -> NSDragOperation { draggingEntered(sender) }
+    func fileDropDraggingUpdated(_ sender: any NSDraggingInfo) -> NSDragOperation { draggingUpdated(sender) }
+    func fileDropDraggingExited(_ sender: (any NSDraggingInfo)?) { draggingExited(sender) }
+    func fileDropPrepareForDragOperation(_ sender: any NSDraggingInfo) -> Bool { prepareForDragOperation(sender) }
+    func fileDropPerformDragOperation(_ sender: any NSDraggingInfo) -> Bool { performDragOperation(sender) }
+    func fileDropConcludeDragOperation(_ sender: (any NSDraggingInfo)?) { concludeDragOperation(sender) }
+}