Fix: Multitouch stability during rapid system changes (#113)

* Fix: Multitouch stability during rapid system changes

* Update MiddleDrag/Managers/DeviceMonitor.swift

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Signed-off-by: Karan Mohindroo <96403086+NullPointerDepressiveDisorder@users.noreply.github.com>

* Update MiddleDrag/MiddleDragTests/MultitouchManagerTests.swift

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Signed-off-by: Karan Mohindroo <96403086+NullPointerDepressiveDisorder@users.noreply.github.com>

---------

Signed-off-by: Karan Mohindroo <96403086+NullPointerDepressiveDisorder@users.noreply.github.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: NullPointerDepressiveDisorder

MiddleDrag/Managers/DeviceMonitor.swift

@@ -54,6 +54,13 @@ import os
     }
     unsafe os_unfair_lock_unlock(&gCallbackLock)
 
+    // Additional safety check: Verify the monitor instance is still valid and running.
+    unsafe monitor.stateLock.lock()
+    let monitorIsRunning = unsafe monitor.isRunning
+    unsafe monitor.stateLock.unlock()
+    
+    guard monitorIsRunning else { return 0 }
+    
     #if DEBUG
         unsafe touchCount += 1
         // Log sparingly to avoid performance impact
@@ -90,11 +97,7 @@ class DeviceMonitor: TouchDeviceProviding {
     /// Delay between unregistering callbacks and stopping devices.
     /// This allows the MultitouchSupport framework's internal thread (mt_ThreadedMTEntry)
     /// to complete any in-flight callback processing before we stop devices.
-    /// Value determined empirically: 500ms is sufficient to avoid CFRelease(NULL) crashes
-    /// and EXC_BREAKPOINT exceptions during rapid connectivity changes (wifi ↔ none).
-    /// Increased from 100ms to handle rapid connectivity toggling that triggers multiple
-    /// restart cycles in quick succession.
-    static let frameworkCleanupDelay: TimeInterval = 0.5
+    static let frameworkCleanupDelay: TimeInterval = 1.0
 
     // MARK: - Properties
 
@@ -103,10 +106,10 @@ class DeviceMonitor: TouchDeviceProviding {
 
     nonisolated(unsafe) private var device: MTDeviceRef?
     nonisolated(unsafe) private var registeredDevices: Set<UnsafeMutableRawPointer> = unsafe []
-    private var isRunning = false
+    fileprivate var isRunning = false
 
     /// Lock to protect concurrent access to device state during stop/start operations
-    private let stateLock = NSLock()
+    fileprivate let stateLock = NSLock()
 
     /// Tracks whether this instance owns the global callback reference
     private var ownsGlobalReference = false

MiddleDrag/Managers/MultitouchManager.swift

@@ -11,18 +11,14 @@ public final class MultitouchManager: @unchecked Sendable {
     /// Delay after stopping before restarting devices during wake-from-sleep.
     /// This allows the MultitouchSupport framework's internal thread (mt_ThreadedMTEntry)
     /// to fully complete cleanup before we start new devices.
-    /// Value determined empirically: 500ms is sufficient to avoid CFRelease(NULL) crashes
-    /// and EXC_BREAKPOINT exceptions during rapid connectivity changes (wifi ↔ none).
-    /// Increased from 250ms to handle rapid connectivity toggling that triggers multiple
-    /// restart cycles in quick succession.
-    static let restartCleanupDelay: TimeInterval = 0.5
+    static let restartCleanupDelay: TimeInterval = 1.0
 
     /// Minimum delay between restart operations to prevent race conditions.
     /// When multiple restart triggers occur in rapid succession (e.g., rapid connectivity
     /// changes wifi ↔ none), we debounce them by waiting at least this long after the
     /// last restart completed. This prevents overlapping restart attempts that can expose
     /// race conditions in the MultitouchSupport framework's internal thread.
-    static let minimumRestartInterval: TimeInterval = 0.6
+    static let minimumRestartInterval: TimeInterval = 2.5
 
     /// Initial interval between polling attempts when no multitouch device is found at launch.
     /// This handles Bluetooth trackpads that connect after login (common during boot).

MiddleDrag/MiddleDragTests/DeviceMonitorTests.swift

@@ -267,7 +267,7 @@ import XCTest
             DeviceMonitor.frameworkCleanupDelay, 0,
             "frameworkCleanupDelay should be positive")
         unsafe XCTAssertLessThanOrEqual(
-            DeviceMonitor.frameworkCleanupDelay, 0.5,
+            DeviceMonitor.frameworkCleanupDelay, 1.0,
             "frameworkCleanupDelay should not be excessive")
     }
 

MiddleDrag/MiddleDragTests/MultitouchManagerTests.swift

@@ -212,7 +212,7 @@ final class MultitouchManagerTests: XCTestCase {
         ) {
             expectation.fulfill()
         }
-        wait(for: [expectation], timeout: 1.0)
+        wait(for: [expectation], timeout: 2.0)
 
         XCTAssertFalse(manager.isMonitoring)
         XCTAssertFalse(manager.isEnabled)
@@ -303,7 +303,7 @@ final class MultitouchManagerTests: XCTestCase {
         ) {
             expectation.fulfill()
         }
-        wait(for: [expectation], timeout: 1.0)
+        wait(for: [expectation], timeout: 3.0)
 
         // We expect:
         // 1 initial creation
@@ -339,7 +339,7 @@ final class MultitouchManagerTests: XCTestCase {
         ) {
             expectation.fulfill()
         }
-        wait(for: [expectation], timeout: 1.0)
+        wait(for: [expectation], timeout: 3.0)
 
         // Verify manager is still stopped
         XCTAssertFalse(manager.isMonitoring, "Manager should remain stopped")
@@ -1688,7 +1688,7 @@ final class MultitouchManagerTests: XCTestCase {
         ) {
             expectation.fulfill()
         }
-        wait(for: [expectation], timeout: 1.0)
+        wait(for: [expectation], timeout: 3.0)
 
         // After restart, monitoring should still be active
         XCTAssertTrue(manager.isMonitoring)
@@ -1722,7 +1722,7 @@ final class MultitouchManagerTests: XCTestCase {
         ) {
             expectation.fulfill()
         }
-        wait(for: [expectation], timeout: 1.0)
+        wait(for: [expectation], timeout: 3.0)
 
         XCTAssertFalse(manager.isEnabled)
         XCTAssertTrue(manager.isMonitoring)
@@ -1767,7 +1767,7 @@ final class MultitouchManagerTests: XCTestCase {
         ) {
             restartExpectation.fulfill()
         }
-        wait(for: [restartExpectation], timeout: 1.0)
+        wait(for: [restartExpectation], timeout: 3.0)
 
         XCTAssertTrue(manager.isMonitoring)
 
@@ -1806,7 +1806,7 @@ final class MultitouchManagerTests: XCTestCase {
         ) {
             expectation.fulfill()
         }
-        wait(for: [expectation], timeout: 1.0)
+        wait(for: [expectation], timeout: 3.0)
 
         unsafe XCTAssertEqual(mockDevice.startCallCount, 2)  // Now restarted
 
@@ -1819,7 +1819,7 @@ final class MultitouchManagerTests: XCTestCase {
             MultitouchManager.restartCleanupDelay, 0,
             "restartCleanupDelay should be positive")
         XCTAssertLessThanOrEqual(
-            MultitouchManager.restartCleanupDelay, 0.5,
+            MultitouchManager.restartCleanupDelay, 1.0,
             "restartCleanupDelay should not be excessive")
     }
 
@@ -1829,7 +1829,7 @@ final class MultitouchManagerTests: XCTestCase {
             MultitouchManager.minimumRestartInterval, 0,
             "minimumRestartInterval should be positive")
         XCTAssertLessThanOrEqual(
-            MultitouchManager.minimumRestartInterval, 1.0,
+            MultitouchManager.minimumRestartInterval, 2.5,
             "minimumRestartInterval should not be excessive")
     }
 
@@ -1863,7 +1863,7 @@ final class MultitouchManagerTests: XCTestCase {
         ) {
             expectation.fulfill()
         }
-        wait(for: [expectation], timeout: 2.0)
+        wait(for: [expectation], timeout: 5.0)
 
         // We expect far fewer than 10 device creations due to:
         // 1. The first restart being in progress blocks subsequent ones
@@ -1903,7 +1903,7 @@ final class MultitouchManagerTests: XCTestCase {
         ) {
             expectation.fulfill()
         }
-        wait(for: [expectation], timeout: 1.0)
+        wait(for: [expectation], timeout: 3.0)
 
         // Only 2 device creations: initial start + one restart
         // The duplicate restart calls while in progress should have been skipped
@@ -1933,7 +1933,7 @@ final class MultitouchManagerTests: XCTestCase {
         ) {
             expectation.fulfill()
         }
-        wait(for: [expectation], timeout: 3.0)
+        wait(for: [expectation], timeout: 5.0)
 
         // Should still be monitoring after all restarts
         XCTAssertTrue(manager.isMonitoring)
@@ -1980,7 +1980,7 @@ final class MultitouchManagerTests: XCTestCase {
         ) {
             restartExpectation.fulfill()
         }
-        wait(for: [restartExpectation], timeout: 1.0)
+        wait(for: [restartExpectation], timeout: 3.0)
 
         XCTAssertTrue(manager.isMonitoring)