fix: better handle palm/fingers resting on the trackpad (closes #5191)

src/logic/events/TrackpadEvents.swift

@@ -20,6 +20,14 @@ class TrackpadEvents {
         }
     }
 
+    static func reset() {
+        ScrollwheelEvents.toggle(false)
+        NavigationSwipeDetector.reset()
+        NonFreshGestureDetector.reset()
+        // no need to call TriggerSwipeDetector.reset; it does it itself when triggering
+        TriggerSwipeDetector.maxFingersDownDuringTrigger = 0
+    }
+
     private static func observe_() {
         // CGEvent.tapCreate returns null if ensureAccessibilityCheckboxIsChecked() didn't pass
         eventTap = CGEvent.tapCreate(
@@ -51,39 +59,40 @@ class TrackpadEvents {
     private static func touchEventHandler(_ cgEvent: CGEvent) -> Bool {
         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) }
+        // Logger.error { (touches.count, touches.map { $0.phase.readable }) }
+        // macOS often sends faulty events with no touches between valid events; we ignore these as they would break our gesture logic
+        guard touches.count > 0 else  { return false }
+        // isResting seems to always return false. It's not doing its job to detect resting thumb/palm/finger
+        // on macOS, the finger contact surface is not exposed in NSTouch, so we can't detect big contact == palm, for example
+        // the closest thing we can do to detect resting inputs is remove touches which have .phase == .stationary
+        let activeTouches = touches.filter { !$0.isResting && ($0.phase == .began || $0.phase == .moved) }
+        let fingersDown = touches.count { $0.phase == .began || $0.phase == .moved || $0.phase == .stationary }
         let requiredFingers = Preferences.nextWindowGesture.isThreeFinger() ? 3 : 4
         if App.app.appIsBeingUsed {
-            handleEventIfAppIsBeingUsed(activeTouches, requiredFingers)
+            handleEventIfAppIsBeingUsed(fingersDown, activeTouches, requiredFingers)
             return true // absorb the touch event
         }
-        return handleEventIfAppIsNotBeingUsed(touches, activeTouches, requiredFingers) // absorb or not the touch event, depending on the situation
+        return handleEventIfAppIsNotBeingUsed(fingersDown, activeTouches, requiredFingers) // absorb or not the touch event, depending on the situation
     }
 
-    private static func handleEventIfAppIsBeingUsed(_ activeTouches: Set<NSTouch>, _ requiredFingers: Int) {
-        if activeTouches.count == 0 {
-            NavigationSwipeDetector.reset()
+    private static func handleEventIfAppIsBeingUsed(_ fingersDown: Int, _ activeTouches: Set<NSTouch>, _ requiredFingers: Int) {
+        if fingersDown <= TriggerSwipeDetector.maxFingersDownDuringTrigger - requiredFingers {
             if App.app.shortcutIndex == Preferences.gestureIndex && !App.app.forceDoNothingOnRelease && Preferences.shortcutStyle[App.app.shortcutIndex] == .focusOnRelease {
                 DispatchQueue.main.async {
-                    ScrollwheelEvents.toggle(false)
                     App.app.focusTarget()
                 }
             }
-        } else if activeTouches.count > 1 {
+            return
+        }
+        if activeTouches.count > 1 {
             CursorEvents.deadZoneInitialPosition = nil
             NavigationSwipeDetector.hasDetected(activeTouches)
-        } else {
-            // if activeTouches.count == 1, ignore (finger is in pointer-mode)
         }
+        // if activeTouches.count == 1, ignore (finger is in pointer-mode)
     }
 
-    private static func handleEventIfAppIsNotBeingUsed(_ touches: Set<NSTouch>, _ activeTouches: Set<NSTouch>, _ requiredFingers: Int) -> Bool {
-        if touches.count <= 1 {
+    private static func handleEventIfAppIsNotBeingUsed(_ fingersDown: Int, _ activeTouches: Set<NSTouch>, _ requiredFingers: Int) -> Bool {
+        if fingersDown <= 1 {
             NonFreshGestureDetector.reset()
             return false // don't absorb the touch event
         }
@@ -94,7 +103,7 @@ class TrackpadEvents {
             TriggerSwipeDetector.reset()
             return false // don't absorb the touch event
         } else {
-            return TriggerSwipeDetector.hasDetected(activeTouches) // absorb or not the touch event, depending on the situation
+            return TriggerSwipeDetector.hasDetected(fingersDown, activeTouches) // absorb or not the touch event, depending on the situation
         }
     }
 }
@@ -127,12 +136,15 @@ class TriggerSwipeDetector {
     // when the native using 3-finger swipe to shift Space, macOS will prevent a swipe until the fingers are raised,
     // if the user moves too much in the vertical direction. We imitate this behavior
     static let MAX_SWIPE_DISTANCE_IN_WRONG_DIRECTION: Double = 0.1 // % of trackpad surface traveled
+    // if there are extra non-active fingers during the gesture trigger, we remember it so we can ignore those extra fingers to detect intent to focus on release
+    static var maxFingersDownDuringTrigger = 0
 
     private static var gestureTracker = GestureTracker()
     private static var swipeStillPossible = true
 
-    static func hasDetected(_ activeTouches: Set<NSTouch>) -> Bool {
+    static func hasDetected(_ fingersDown: Int, _ activeTouches: Set<NSTouch>) -> Bool {
         guard swipeStillPossible && !gestureTracker.isNewGesture(activeTouches) else { return false }
+        maxFingersDownDuringTrigger = max(maxFingersDownDuringTrigger, fingersDown)
         let distances = gestureTracker.computeDistance(activeTouches)
         for distance in distances {
             let (absX, absY) = (abs(distance.x), abs(distance.y))

src/ui/App.swift

@@ -64,7 +64,7 @@ class App: AppCenterApplication {
         forceDoNothingOnRelease = false
         MouseEvents.toggle(false)
         CursorEvents.toggle(false)
-        ScrollwheelEvents.toggle(false)
+        TrackpadEvents.reset()
         hideThumbnailPanelWithoutChangingKeyWindow()
         if !keepPreview {
             previewPanel.orderOut(nil)