Wait for modifier keys to release before moving items

As a result of this change, we can remove the command key check in the layout bar.

This commit also simplifies other waiters belonging to the menu bar item manager.

Ice/MenuBar/MenuBarItems/MenuBarItemManager.swift

@@ -479,26 +479,33 @@ extension MenuBarItemManager {
 // MARK: - Async Waiters
 
 extension MenuBarItemManager {
+    /// Waits asynchronously for the given operation to complete.
+    /// 
+    /// - Parameters:
+    ///   - timeout: Amount of time to wait before throwing an error.
+    ///   - operation: The operation to perform.
+    private func waitWithTask(timeout: Duration?, operation: @escaping @Sendable () async throws -> Void) async throws {
+        let task = if let timeout {
+            Task(timeout: timeout, operation: operation)
+        } else {
+            Task(operation: operation)
+        }
+        try await task.value
+    }
+
     /// Waits asynchronously for all menu bar items to stop moving.
     ///
     /// - Parameter timeout: Amount of time to wait before throwing an error.
     func waitForItemsToStopMoving(timeout: Duration? = nil) async throws {
-        let taskBody: @Sendable () async throws -> Void = {
-            while await self.isMovingItem {
+        try await waitWithTask(timeout: timeout) { [weak self] in
+            guard let self else {
+                return
+            }
+            while await isMovingItem {
                 try Task.checkCancellation()
                 try await Task.sleep(for: .milliseconds(10))
             }
         }
-        let checkTask = if let timeout {
-            Task(timeout: timeout) {
-                try await taskBody()
-            }
-        } else {
-            Task {
-                try await taskBody()
-            }
-        }
-        try await checkTask.value
     }
 
     /// Waits asynchronously for the mouse to stop moving.
@@ -507,10 +514,13 @@ extension MenuBarItemManager {
     ///   - threshold: A threshold to use to determine whether the mouse has stopped moving.
     ///   - timeout: Amount of time to wait before throwing an error.
     func waitForMouseToStopMoving(threshold: TimeInterval = 0.1, timeout: Duration? = nil) async throws {
-        let taskBody: @Sendable () async throws -> Void = {
+        try await waitWithTask(timeout: timeout) { [weak self] in
+            guard let self else {
+                return
+            }
             while true {
                 try Task.checkCancellation()
-                guard let date = await self.lastMouseMoveStartDate else {
+                guard let date = await lastMouseMoveStartDate else {
                     break
                 }
                 if Date.now.timeIntervalSince(date) > threshold {
@@ -519,16 +529,34 @@ extension MenuBarItemManager {
                 try await Task.sleep(for: .milliseconds(10))
             }
         }
-        let checkTask = if let timeout {
-            Task(timeout: timeout) {
-                try await taskBody()
+    }
+
+    /// Waits asynchronously until no modifier keys are pressed.
+    ///
+    /// - Parameter timeout: Amount of time to wait before throwing an error.
+    func waitForNoModifiersPressed(timeout: Duration? = nil) async throws {
+        try await waitWithTask(timeout: timeout) {
+            // Return early if no flags are pressed.
+            if NSEvent.modifierFlags.isEmpty {
+                return
             }
-        } else {
-            Task {
-                try await taskBody()
+
+            var cancellable: AnyCancellable?
+
+            await withCheckedContinuation { continuation in
+                cancellable = Publishers.Merge(
+                    UniversalEventMonitor.publisher(for: .flagsChanged),
+                    RunLoopLocalEventMonitor.publisher(for: .flagsChanged, mode: .eventTracking)
+                )
+                .removeDuplicates()
+                .sink { _ in
+                    if NSEvent.modifierFlags.isEmpty {
+                        cancellable?.cancel()
+                        continuation.resume()
+                    }
+                }
             }
         }
-        try await checkTask.value
     }
 }
 
@@ -1051,6 +1079,9 @@ extension MenuBarItemManager {
         }
 
         do {
+            // Order of these waiters matters, as the modifiers could be released
+            // while the mouse is still moving.
+            try await waitForNoModifiersPressed()
             try await waitForMouseToStopMoving()
         } catch {
             throw EventError(code: .couldNotComplete, item: item)

Ice/UI/LayoutBar/LayoutBarItemView.swift

@@ -121,14 +121,6 @@ final class LayoutBarItemView: NSView {
         return alert
     }
 
-    /// Provides an alert to display when the user is pressing the Command key
-    /// while moving a menu bar item.
-    func provideAlertForCommandKeyDown() -> NSAlert {
-        let alert = NSAlert()
-        alert.messageText = "Do not hold the Command key while moving a menu bar item."
-        return alert
-    }
-
     override func draw(_ dirtyRect: NSRect) {
         if !isDraggingPlaceholder {
             image?.draw(
@@ -160,12 +152,6 @@ final class LayoutBarItemView: NSView {
     override func mouseDragged(with event: NSEvent) {
         super.mouseDragged(with: event)
 
-        guard !event.modifierFlags.contains(.command) else {
-            let alert = provideAlertForCommandKeyDown()
-            alert.runModal()
-            return
-        }
-
         guard isEnabled else {
             let alert = provideAlertForDisabledItem()
             alert.runModal()

Ice/UI/LayoutBar/LayoutBarPaddingView.swift

@@ -91,10 +91,7 @@ final class LayoutBarPaddingView: NSView {
             }
         }
 
-        guard
-            sender.draggingSourceOperationMask == .move,
-            let draggingSource = sender.draggingSource as? LayoutBarItemView
-        else {
+        guard let draggingSource = sender.draggingSource as? LayoutBarItemView else {
             return false
         }