feat: improve accidental cursor movement

see https://github.com/lwouis/alt-tab-macos/issues/4278#issuecomment-3733280737

alt-tab-macos.xcodeproj/project.pbxproj

@@ -101,6 +101,7 @@
 		BF0C827C61136E83F43C6436 /* InfoPlist.strings in Resources */ = {isa = PBXBuildFile; fileRef = BF0C8913DCD0FE4C494055B6 /* InfoPlist.strings */; };
 		BF0C828D53D429C2B8B22391 /* Localizable.strings in Resources */ = {isa = PBXBuildFile; fileRef = BF0C883EBA8FDA9CB61C91FD /* Localizable.strings */; };
 		BF0C829583ED47E458528F3A /* accessibility@2x.png in Resources */ = {isa = PBXBuildFile; fileRef = BF0C889529FF19620EDAC295 /* accessibility@2x.png */; };
+		BF0C82E9AB495AAAA182764A /* CursorEvents.swift in Sources */ = {isa = PBXBuildFile; fileRef = BF0C81DD40D5AAD9B7C09028 /* CursorEvents.swift */; };
 		BF0C832C5BF4C8E9C95F7767 /* MissionControl.swift in Sources */ = {isa = PBXBuildFile; fileRef = BF0C82E4DE5A28800F1DA6E6 /* MissionControl.swift */; };
 		BF0C83578F7292F307E30751 /* PopupButtonLikeSystemSettings.swift in Sources */ = {isa = PBXBuildFile; fileRef = BF0C8A479D2B7FB80531F037 /* PopupButtonLikeSystemSettings.swift */; };
 		BF0C836CC0D9CEE5026B8EF4 /* InfoPlist.strings in Resources */ = {isa = PBXBuildFile; fileRef = BF0C83121AAE4437993B4FF3 /* InfoPlist.strings */; };
@@ -387,6 +388,7 @@
 		BF0C81BB57B297B2432C4824 /* test-release.xcconfig */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.xcconfig; path = "test-release.xcconfig"; sourceTree = "<group>"; };
 		BF0C81BF699036148BA17B7C /* jv */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.plist.strings; name = jv; path = Localizable.strings; sourceTree = "<group>"; };
 		BF0C81D602ED642A48D50B78 /* notarytool */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text; path = notarytool; sourceTree = "<group>"; };
+		BF0C81DD40D5AAD9B7C09028 /* CursorEvents.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = CursorEvents.swift; sourceTree = "<group>"; };
 		BF0C82009DCCA86287730F13 /* th */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.plist.strings; name = th; path = InfoPlist.strings; sourceTree = "<group>"; };
 		BF0C821029C1CBAC09232B0B /* nn */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.plist.strings; name = nn; path = InfoPlist.strings; sourceTree = "<group>"; };
 		BF0C822D3BEDAB1F1C9F775E /* ScreensEvents.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = ScreensEvents.swift; sourceTree = "<group>"; };
@@ -1898,6 +1900,7 @@
 				BF0C8643F524515224BF1618 /* KeyboardEventsTestable.swift */,
 				BF0C8C69316EAAF6DC9AE391 /* CliEvents.swift */,
 				BF0C8FAF34022E23582797F3 /* ScrollwheelEvents.swift */,
+				BF0C81DD40D5AAD9B7C09028 /* CursorEvents.swift */,
 			);
 			path = events;
 			sourceTree = "<group>";
@@ -2476,6 +2479,7 @@
 				BF0C8E5F4E4D5F7DAEE07C20 /* ThumbnailsPanelBackgroundView.swift in Sources */,
 				BF0C8AD478399D2E97AE3FB4 /* CustomRecorderControlTestable.swift in Sources */,
 				BF0C8A5FA46C5E74A071FF4C /* ScrollwheelEvents.swift in Sources */,
+				BF0C82E9AB495AAAA182764A /* CursorEvents.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};

src/api-wrappers/HelperExtensions.swift

@@ -381,3 +381,17 @@ extension String.StringInterpolation {
         }
     }
 }
+
+extension CGEvent {
+    func toNSEvent() -> NSEvent? {
+        if Thread.isMainThread {
+            return NSEvent(cgEvent: self)
+        }
+        // conversion has to happen on the main-thread, or appkit will crash
+        var nsEvent: NSEvent?
+        DispatchQueue.main.sync {
+            nsEvent = NSEvent(cgEvent: self)
+        }
+        return nsEvent
+    }
+}

src/logic/events/CursorEvents.swift

@@ -0,0 +1,69 @@
+import Cocoa
+import Carbon.HIToolbox.Events
+
+class CursorEvents {
+    private static var eventTap: CFMachPort!
+    private static var shouldBeEnabled: Bool!
+    static var deadZoneInitialPosition: CGPoint?
+    static var isAllowedToMouseHover = true
+
+    static func observe() {
+        observe_()
+    }
+
+    static func toggle(_ enabled: Bool) {
+        guard enabled != shouldBeEnabled else { return }
+        shouldBeEnabled = enabled
+        if !enabled {
+            deadZoneInitialPosition = nil
+        }
+        if let eventTap {
+            CGEvent.tapEnable(tap: eventTap, enable: enabled)
+        }
+    }
+
+    private static func observe_() {
+        let eventMask = [CGEventType.mouseMoved].reduce(CGEventMask(0), { $0 | (1 << $1.rawValue) })
+        // CGEvent.tapCreate returns nil if ensureAccessibilityCheckboxIsChecked() didn't pass
+        eventTap = CGEvent.tapCreate(
+            tap: .cgSessionEventTap,
+            place: .headInsertEventTap,
+            options: .defaultTap,
+            eventsOfInterest: eventMask,
+            callback: handleEvent,
+            userInfo: nil)
+        if let eventTap {
+            toggle(false)
+            let runLoopSource = CFMachPortCreateRunLoopSource(nil, eventTap, 0)
+            // we run on main-thread directly since all we do is check NSEvent data, which we must do on main-thread
+            CFRunLoopAddSource(CFRunLoopGetMain(), runLoopSource, .commonModes)
+        } else {
+            App.app.restart()
+        }
+    }
+
+    private static let handleEvent: CGEventTapCallBack = { _, type, cgEvent, _ in
+        if type == .mouseMoved {
+            updateDeadzoneSituation(cgEvent)
+        } else if (type == .tapDisabledByUserInput || type == .tapDisabledByTimeout) && shouldBeEnabled {
+            CGEvent.tapEnable(tap: eventTap!, enable: true)
+        }
+        return Unmanaged.passUnretained(cgEvent) // focused app will receive the event
+    }
+
+    /// 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) {
+        guard let event = cgEvent.toNSEvent() else { return }
+        guard let deadZoneInitialPosition else {
+            deadZoneInitialPosition = event.locationInWindow
+            isAllowedToMouseHover = false
+            return
+        }
+        let deltaX = event.locationInWindow.x - deadZoneInitialPosition.x
+        let deltaY = event.locationInWindow.y - deadZoneInitialPosition.y
+        let d = hypot(deltaX, deltaY)
+        Logger.error { d }
+        isAllowedToMouseHover = d > 25
+    }
+}

src/logic/events/MouseEvents.swift

@@ -28,7 +28,7 @@ class MouseEvents {
             callback: handleEvent,
             userInfo: nil)
         if let eventTap {
-            MouseEvents.toggle(false)
+            toggle(false)
             let runLoopSource = CFMachPortCreateRunLoopSource(nil, eventTap, 0)
             // we run on main-thread directly since all we do is check UI coordinates, which we must do on main-thread
             CFRunLoopAddSource(CFRunLoopGetMain(), runLoopSource, .commonModes)

src/logic/events/TrackpadEvents.swift

@@ -4,6 +4,7 @@ import Cocoa
 class TrackpadEvents {
     private static var eventTap: CFMachPort!
     private static var shouldBeEnabled: Bool!
+    private static var cursorMovedDistance = CGFloat(0.0)
 
     static func observe() {
         observe_()
@@ -48,15 +49,15 @@ class TrackpadEvents {
     }
 
     private static func touchEventHandler(_ cgEvent: CGEvent) -> Bool {
-        guard let nsEvent = convertEvent(cgEvent) else { return false } // don't absorb the touch event
+        guard let nsEvent = cgEvent.toNSEvent() else { return false } // don't absorb the touch event
         let touches = nsEvent.allTouches()
+        // Logger.error { (touches.count, touches.map { $0.phase.readable}) }
         // sometimes the os sends events with no touches; we ignore these as they could break our gesture logic
         if touches.count == 0 {
             return false
         }
         let activeTouches = touches.filter { !$0.isResting && ($0.phase == .began || $0.phase == .moved || $0.phase == .stationary) }
         let requiredFingers = Preferences.nextWindowGesture.isThreeFinger() ? 3 : 4
-        // Logger.error("---", "activeTouches:", activeTouches.count, "all:", touches.map { $0.phase.readable }, requiredFingers)
         if App.app.appIsBeingUsed {
             handleEventIfAppIsBeingUsed(activeTouches, requiredFingers)
             return true // absorb the touch event
@@ -74,6 +75,7 @@ class TrackpadEvents {
                 }
             }
         } else if activeTouches.count > 1 {
+            CursorEvents.deadZoneInitialPosition = nil
             NavigationSwipeDetector.hasDetected(activeTouches)
         } else {
             // if activeTouches.count == 1, ignore (finger is in pointer-mode)
@@ -232,12 +234,3 @@ fileprivate func performHapticFeedback() {
         NSHapticFeedbackManager.defaultPerformer.perform(.generic, performanceTime: .default)
     }
 }
-
-fileprivate func convertEvent(_ cgEvent: CGEvent) -> NSEvent? {
-    var nsEvent: NSEvent?
-    // conversion has to happen on the main-thread, or appkit will crash
-    DispatchQueue.main.sync {
-        nsEvent = NSEvent(cgEvent: cgEvent)
-    }
-    return nsEvent
-}

src/ui/App.swift

@@ -63,6 +63,7 @@ class App: AppCenterApplication {
         isFirstSummon = true
         forceDoNothingOnRelease = false
         MouseEvents.toggle(false)
+        CursorEvents.toggle(false)
         ScrollwheelEvents.toggle(false)
         hideThumbnailPanelWithoutChangingKeyWindow()
         if !keepPreview {
@@ -314,6 +315,7 @@ extension App: NSApplicationDelegate {
         self.feedbackWindow = FeedbackWindow()
         KeyboardEvents.addEventHandlers()
         MouseEvents.observe()
+        CursorEvents.observe()
         TrackpadEvents.observe()
         CliEvents.observe()
         // login item and plist updates can be done a bit later, to accelerate launch

src/ui/main-window/ThumbnailsPanel.swift

@@ -71,6 +71,7 @@ class ThumbnailsPanel: NSPanel {
         alphaValue = 1
         makeKeyAndOrderFront(nil)
         MouseEvents.toggle(true)
+        CursorEvents.toggle(true)
         thumbnailsView.scrollView.flashScrollers()
     }
 

src/ui/main-window/ThumbnailsView.swift

@@ -290,7 +290,7 @@ class ScrollView: NSScrollView {
     }
 
     override func mouseMoved(with event: NSEvent) {
-        guard let documentView, !isCurrentlyScrolling && !ScrollwheelEvents.shouldBeEnabled else { return }
+        guard let documentView, !isCurrentlyScrolling && CursorEvents.isAllowedToMouseHover else { return }
         let location = documentView.convert(App.app.thumbnailsPanel.mouseLocationOutsideOfEventStream, from: nil)
         let newTarget = findTarget(location)
         guard newTarget !== previousTarget else { return }