From 3205ed46c53cf6bd6fcf4ef0962da148917e573f Mon Sep 17 00:00:00 2001
From: Jakub Piasecki <jakub.piasecki@swmansion.com>
Date: Tue, 18 Oct 2022 16:28:52 +0200
Subject: [PATCH 1/3] Add gesture initialization

---
 .../gesturehandler/GestureHandler.kt          | 61 +++++++++++++------
 .../GestureHandlerOrchestrator.kt             | 19 +-----
 .../gesturehandler/LongPressGestureHandler.kt | 12 ++--
 .../gesturehandler/PanGestureHandler.kt       | 16 +++--
 .../gesturehandler/PinchGestureHandler.kt     | 14 +++--
 .../gesturehandler/RotationGestureHandler.kt  |  8 ++-
 .../gesturehandler/TapGestureHandler.kt       | 12 ++--
 .../react/RNGestureHandlerModule.kt           |  5 +-
 8 files changed, 89 insertions(+), 58 deletions(-)

diff --git a/android/lib/src/main/java/com/swmansion/gesturehandler/GestureHandler.kt b/android/lib/src/main/java/com/swmansion/gesturehandler/GestureHandler.kt
index f690e42efb..2719aff954 100644
--- a/android/lib/src/main/java/com/swmansion/gesturehandler/GestureHandler.kt
+++ b/android/lib/src/main/java/com/swmansion/gesturehandler/GestureHandler.kt
@@ -57,6 +57,7 @@ open class GestureHandler<ConcreteGestureHandlerT : GestureHandler<ConcreteGestu
   var lastAbsolutePositionY = 0f
     private set
 
+  private var isInitialized = false
   private var manualActivation = false
 
   private var lastEventOffsetX = 0f
@@ -68,6 +69,8 @@ open class GestureHandler<ConcreteGestureHandlerT : GestureHandler<ConcreteGestu
   private var onTouchEventListener: OnTouchEventListener? = null
   private var interactionController: GestureHandlerInteractionController? = null
 
+  private var eventTriggeringStateChangeInTouchEventHandler: MotionEvent? = null
+
   @Suppress("UNCHECKED_CAST")
   protected fun self(): ConcreteGestureHandlerT = this as ConcreteGestureHandlerT
 
@@ -88,8 +91,8 @@ open class GestureHandler<ConcreteGestureHandlerT : GestureHandler<ConcreteGestu
     onTouchEventListener?.onHandlerUpdate(self(), event)
   }
 
-  open fun dispatchTouchEvent() {
-    if (changedTouchesPayload != null) {
+  open fun tryDispatchingTouchEvent() {
+    if (needsPointerData && changedTouchesPayload != null) {
       onTouchEventListener?.onTouchEvent(self())
     }
   }
@@ -372,7 +375,7 @@ open class GestureHandler<ConcreteGestureHandlerT : GestureHandler<ConcreteGestu
     }
   }
 
-  private fun dispatchTouchDownEvent(event: MotionEvent) {
+  private fun handleTouchDownEvent(event: MotionEvent) {
     changedTouchesPayload = null
     touchEventType = RNGestureHandlerTouchEvent.EVENT_TOUCH_DOWN
     val pointerId = event.getPointerId(event.actionIndex)
@@ -390,10 +393,10 @@ open class GestureHandler<ConcreteGestureHandlerT : GestureHandler<ConcreteGestu
     addChangedPointer(trackedPointers[pointerId]!!)
     extractAllPointersData()
 
-    dispatchTouchEvent()
+    tryDispatchingTouchEvent()
   }
 
-  private fun dispatchTouchUpEvent(event: MotionEvent) {
+  private fun handleTouchUpEvent(event: MotionEvent) {
     extractAllPointersData()
     changedTouchesPayload = null
     touchEventType = RNGestureHandlerTouchEvent.EVENT_TOUCH_UP
@@ -412,10 +415,10 @@ open class GestureHandler<ConcreteGestureHandlerT : GestureHandler<ConcreteGestu
     trackedPointers[pointerId] = null
     trackedPointersCount--
 
-    dispatchTouchEvent()
+    tryDispatchingTouchEvent()
   }
 
-  private fun dispatchTouchMoveEvent(event: MotionEvent) {
+  private fun handleTouchMoveEvent(event: MotionEvent) {
     changedTouchesPayload = null
     touchEventType = RNGestureHandlerTouchEvent.EVENT_TOUCH_MOVE
     val offsetX = event.rawX - event.x
@@ -442,20 +445,28 @@ open class GestureHandler<ConcreteGestureHandlerT : GestureHandler<ConcreteGestu
     // only info about one pointer)
     if (pointersAdded > 0) {
       extractAllPointersData()
-      dispatchTouchEvent()
+      tryDispatchingTouchEvent()
     }
   }
 
-  fun updatePointerData(event: MotionEvent) {
-    if (event.actionMasked == MotionEvent.ACTION_DOWN || event.actionMasked == MotionEvent.ACTION_POINTER_DOWN) {
-      dispatchTouchDownEvent(event)
-      dispatchTouchMoveEvent(event)
-    } else if (event.actionMasked == MotionEvent.ACTION_UP || event.actionMasked == MotionEvent.ACTION_POINTER_UP) {
-      dispatchTouchMoveEvent(event)
-      dispatchTouchUpEvent(event)
-    } else if (event.actionMasked == MotionEvent.ACTION_MOVE) {
-      dispatchTouchMoveEvent(event)
+  fun updatePointerData(event: MotionEvent, sourceEvent: MotionEvent) {
+    eventTriggeringStateChangeInTouchEventHandler = sourceEvent
+
+    when (event.actionMasked) {
+        MotionEvent.ACTION_DOWN, MotionEvent.ACTION_POINTER_DOWN -> {
+          handleTouchDownEvent(event)
+          handleTouchMoveEvent(event)
+        }
+        MotionEvent.ACTION_UP, MotionEvent.ACTION_POINTER_UP -> {
+          handleTouchMoveEvent(event)
+          handleTouchUpEvent(event)
+        }
+        MotionEvent.ACTION_MOVE -> {
+          handleTouchMoveEvent(event)
+        }
     }
+
+    eventTriggeringStateChangeInTouchEventHandler = null
   }
 
   private fun extractAllPointersData() {
@@ -482,7 +493,7 @@ open class GestureHandler<ConcreteGestureHandlerT : GestureHandler<ConcreteGestu
     trackedPointersCount = 0
     trackedPointers.fill(null)
 
-    dispatchTouchEvent()
+    tryDispatchingTouchEvent()
   }
 
   private fun addChangedPointer(pointerData: PointerData) {
@@ -659,6 +670,17 @@ open class GestureHandler<ConcreteGestureHandlerT : GestureHandler<ConcreteGestu
     }
   }
 
+  fun initialize(withEvent: MotionEvent? = null) {
+    if (!isInitialized) {
+      val event = withEvent ?: eventTriggeringStateChangeInTouchEventHandler ?: throw IllegalStateException("No event to initialize handler")
+      onInitialize(event)
+    }
+
+    isInitialized = true
+  }
+
+  open fun onInitialize(event: MotionEvent) {}
+
   // responsible for resetting the state of handler upon activation (may be called more than once
   // if the handler is waiting for failure of other one)
   open fun resetProgress() {}
@@ -695,6 +717,7 @@ open class GestureHandler<ConcreteGestureHandlerT : GestureHandler<ConcreteGestu
     trackedPointersCount = 0
     trackedPointers.fill(null)
     touchEventType = RNGestureHandlerTouchEvent.EVENT_UNDETERMINED
+    isInitialized = false
     onReset()
   }
 
@@ -774,7 +797,7 @@ open class GestureHandler<ConcreteGestureHandlerT : GestureHandler<ConcreteGestu
     }
   }
 
-  private data class PointerData(
+  data class PointerData(
     val pointerId: Int,
     var x: Float,
     var y: Float,
diff --git a/android/lib/src/main/java/com/swmansion/gesturehandler/GestureHandlerOrchestrator.kt b/android/lib/src/main/java/com/swmansion/gesturehandler/GestureHandlerOrchestrator.kt
index d4380a2faa..2bb9f62637 100644
--- a/android/lib/src/main/java/com/swmansion/gesturehandler/GestureHandlerOrchestrator.kt
+++ b/android/lib/src/main/java/com/swmansion/gesturehandler/GestureHandlerOrchestrator.kt
@@ -253,21 +253,10 @@ class GestureHandlerOrchestrator(
 
     val action = sourceEvent.actionMasked
     val event = transformEventToViewCoords(handler.view, MotionEvent.obtain(sourceEvent))
-    
-    // Touch events are sent before the handler itself has a chance to process them,
-    // mainly because `onTouchesUp` shoul be send befor gesture finishes. This means that
-    // the first `onTouchesDown` event is sent before a gesture begins, activation in 
-    // callback for this event causes problems because the handler doesn't have a chance
-    // to initialize itself with starting values of pointer (in pan this causes translation
-    // to be equal to the coordinates of the pointer). The simplest solution is to send
-    // the first `onTouchesDown` event after the handler processes it and changes state
-    // to `BEGAN`.
-    if (handler.needsPointerData && handler.state != 0) {
-      handler.updatePointerData(event)
-    }
+
+    handler.updatePointerData(event, sourceEvent)
 
     if (!handler.isAwaiting || action != MotionEvent.ACTION_MOVE) {
-      val isFirstEvent = handler.state == 0
       handler.handle(event, sourceEvent)
       if (handler.isActive) {
         // After handler is done waiting for other one to fail its progress should be
@@ -284,10 +273,6 @@ class GestureHandlerOrchestrator(
         handler.dispatchHandlerUpdate(event)
       }
 
-      if (handler.needsPointerData && isFirstEvent) {
-        handler.updatePointerData(event)
-      }
-
       // if event was of type UP or POINTER_UP we request handler to stop tracking now that
       // the event has been dispatched
       if (action == MotionEvent.ACTION_UP || action == MotionEvent.ACTION_POINTER_UP) {
diff --git a/android/lib/src/main/java/com/swmansion/gesturehandler/LongPressGestureHandler.kt b/android/lib/src/main/java/com/swmansion/gesturehandler/LongPressGestureHandler.kt
index 47a5222c25..b8ec6ac92d 100644
--- a/android/lib/src/main/java/com/swmansion/gesturehandler/LongPressGestureHandler.kt
+++ b/android/lib/src/main/java/com/swmansion/gesturehandler/LongPressGestureHandler.kt
@@ -39,11 +39,8 @@ class LongPressGestureHandler(context: Context) : GestureHandler<LongPressGestur
 
   override fun onHandle(event: MotionEvent, sourceEvent: MotionEvent) {
     if (state == STATE_UNDETERMINED) {
-      previousTime = SystemClock.uptimeMillis()
-      startTime = previousTime
+      initialize(sourceEvent)
       begin()
-      startX = sourceEvent.rawX
-      startY = sourceEvent.rawY
       handler = Handler(Looper.getMainLooper())
       if (minDurationMs > 0) {
         handler!!.postDelayed({ activate() }, minDurationMs)
@@ -83,6 +80,13 @@ class LongPressGestureHandler(context: Context) : GestureHandler<LongPressGestur
     }
   }
 
+  override fun onInitialize(event: MotionEvent) {
+    previousTime = SystemClock.uptimeMillis()
+    startTime = previousTime
+    startX = event.rawX
+    startY = event.rawY
+  }
+
   override fun dispatchStateChange(newState: Int, prevState: Int) {
     previousTime = SystemClock.uptimeMillis()
     super.dispatchStateChange(newState, prevState)
diff --git a/android/lib/src/main/java/com/swmansion/gesturehandler/PanGestureHandler.kt b/android/lib/src/main/java/com/swmansion/gesturehandler/PanGestureHandler.kt
index 7caf07fa55..a41d799c59 100644
--- a/android/lib/src/main/java/com/swmansion/gesturehandler/PanGestureHandler.kt
+++ b/android/lib/src/main/java/com/swmansion/gesturehandler/PanGestureHandler.kt
@@ -223,12 +223,7 @@ class PanGestureHandler(context: Context?) : GestureHandler<PanGestureHandler>()
       lastY = getLastPointerY(sourceEvent, averageTouches)
     }
     if (state == STATE_UNDETERMINED && sourceEvent.pointerCount >= minPointers) {
-      resetProgress()
-      offsetX = 0f
-      offsetY = 0f
-      velocityX = 0f
-      velocityY = 0f
-      velocityTracker = VelocityTracker.obtain()
+      initialize(sourceEvent)
       addVelocityMovement(velocityTracker, sourceEvent)
       begin()
 
@@ -283,6 +278,15 @@ class PanGestureHandler(context: Context?) : GestureHandler<PanGestureHandler>()
     handler?.removeCallbacksAndMessages(null)
   }
 
+  override fun onInitialize(event: MotionEvent) {
+    resetProgress()
+    offsetX = 0f
+    offsetY = 0f
+    velocityX = 0f
+    velocityY = 0f
+    velocityTracker = VelocityTracker.obtain()
+  }
+
   override fun onReset() {
     handler?.removeCallbacksAndMessages(null)
     velocityTracker?.let {
diff --git a/android/lib/src/main/java/com/swmansion/gesturehandler/PinchGestureHandler.kt b/android/lib/src/main/java/com/swmansion/gesturehandler/PinchGestureHandler.kt
index 6f6afd7255..633bf3c468 100644
--- a/android/lib/src/main/java/com/swmansion/gesturehandler/PinchGestureHandler.kt
+++ b/android/lib/src/main/java/com/swmansion/gesturehandler/PinchGestureHandler.kt
@@ -50,11 +50,7 @@ class PinchGestureHandler : GestureHandler<PinchGestureHandler>() {
 
   override fun onHandle(event: MotionEvent, sourceEvent: MotionEvent) {
     if (state == STATE_UNDETERMINED) {
-      val context = view!!.context
-      resetProgress()
-      scaleGestureDetector = ScaleGestureDetector(context, gestureListener)
-      val configuration = ViewConfiguration.get(context)
-      spanSlop = configuration.scaledTouchSlop.toFloat()
+      initialize(sourceEvent)
       begin()
     }
     scaleGestureDetector?.onTouchEvent(sourceEvent)
@@ -89,6 +85,14 @@ class PinchGestureHandler : GestureHandler<PinchGestureHandler>() {
     resetProgress()
   }
 
+  override fun onInitialize(event: MotionEvent) {
+    resetProgress()
+    val context = view!!.context
+    val configuration = ViewConfiguration.get(context)
+    scaleGestureDetector = ScaleGestureDetector(context, gestureListener)
+    spanSlop = configuration.scaledTouchSlop.toFloat()
+  }
+
   override fun resetProgress() {
     velocity = 0.0
     scale = 1.0
diff --git a/android/lib/src/main/java/com/swmansion/gesturehandler/RotationGestureHandler.kt b/android/lib/src/main/java/com/swmansion/gesturehandler/RotationGestureHandler.kt
index e86c7447c1..6c67614020 100644
--- a/android/lib/src/main/java/com/swmansion/gesturehandler/RotationGestureHandler.kt
+++ b/android/lib/src/main/java/com/swmansion/gesturehandler/RotationGestureHandler.kt
@@ -43,8 +43,7 @@ class RotationGestureHandler : GestureHandler<RotationGestureHandler>() {
 
   override fun onHandle(event: MotionEvent, sourceEvent: MotionEvent) {
     if (state == STATE_UNDETERMINED) {
-      resetProgress()
-      rotationGestureDetector = RotationGestureDetector(gestureListener)
+      initialize(sourceEvent)
       begin()
     }
     rotationGestureDetector?.onTouchEvent(sourceEvent)
@@ -70,6 +69,11 @@ class RotationGestureHandler : GestureHandler<RotationGestureHandler>() {
     super.activate(force)
   }
 
+  override fun onInitialize(event: MotionEvent) {
+    resetProgress()
+    rotationGestureDetector = RotationGestureDetector(gestureListener)
+  }
+
   override fun onReset() {
     rotationGestureDetector = null
     anchorX = Float.NaN
diff --git a/android/lib/src/main/java/com/swmansion/gesturehandler/TapGestureHandler.kt b/android/lib/src/main/java/com/swmansion/gesturehandler/TapGestureHandler.kt
index 048abd7b11..73b6cc25d6 100644
--- a/android/lib/src/main/java/com/swmansion/gesturehandler/TapGestureHandler.kt
+++ b/android/lib/src/main/java/com/swmansion/gesturehandler/TapGestureHandler.kt
@@ -108,10 +108,7 @@ class TapGestureHandler : GestureHandler<TapGestureHandler>() {
     val state = state
     val action = sourceEvent.actionMasked
     if (state == STATE_UNDETERMINED) {
-      offsetX = 0f
-      offsetY = 0f
-      startX = getLastPointerX(sourceEvent, true)
-      startY = getLastPointerY(sourceEvent, true)
+      initialize(sourceEvent)
     }
     if (action == MotionEvent.ACTION_POINTER_UP || action == MotionEvent.ACTION_POINTER_DOWN) {
       offsetX += lastX - startX
@@ -148,6 +145,13 @@ class TapGestureHandler : GestureHandler<TapGestureHandler>() {
     end()
   }
 
+  override fun onInitialize(event: MotionEvent) {
+    offsetX = 0f
+    offsetY = 0f
+    startX = getLastPointerX(event, true)
+    startY = getLastPointerY(event, true)
+  }
+
   override fun onCancel() {
     handler?.removeCallbacksAndMessages(null)
   }
diff --git a/android/src/main/java/com/swmansion/gesturehandler/react/RNGestureHandlerModule.kt b/android/src/main/java/com/swmansion/gesturehandler/react/RNGestureHandlerModule.kt
index 86b0fa7c4a..544e9d53bf 100644
--- a/android/src/main/java/com/swmansion/gesturehandler/react/RNGestureHandlerModule.kt
+++ b/android/src/main/java/com/swmansion/gesturehandler/react/RNGestureHandlerModule.kt
@@ -433,9 +433,12 @@ class RNGestureHandlerModule(reactContext: ReactApplicationContext?) :
 
   override fun setGestureHandlerState(handlerTag: Int, newState: Int) {
     registry.getHandler(handlerTag)?.let { handler ->
+      handler.initialize()
+      handler.begin()
+
       when (newState) {
         GestureHandler.STATE_ACTIVE -> handler.activate(force = true)
-        GestureHandler.STATE_BEGAN -> handler.begin()
+        GestureHandler.STATE_BEGAN -> {}
         GestureHandler.STATE_END -> handler.end()
         GestureHandler.STATE_FAILED -> handler.fail()
         GestureHandler.STATE_CANCELLED -> handler.cancel()

From 4d94d159537fea346a37c1ec9294e7d2a2d99cd1 Mon Sep 17 00:00:00 2001
From: Jakub Piasecki <jakub.piasecki@swmansion.com>
Date: Wed, 19 Oct 2022 16:11:31 +0200
Subject: [PATCH 2/3] Make `PointerData` private again Add comments

---
 .../main/java/com/swmansion/gesturehandler/GestureHandler.kt   | 2 +-
 .../swmansion/gesturehandler/react/RNGestureHandlerModule.kt   | 3 +++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/android/lib/src/main/java/com/swmansion/gesturehandler/GestureHandler.kt b/android/lib/src/main/java/com/swmansion/gesturehandler/GestureHandler.kt
index 2719aff954..dd2dd50363 100644
--- a/android/lib/src/main/java/com/swmansion/gesturehandler/GestureHandler.kt
+++ b/android/lib/src/main/java/com/swmansion/gesturehandler/GestureHandler.kt
@@ -797,7 +797,7 @@ open class GestureHandler<ConcreteGestureHandlerT : GestureHandler<ConcreteGestu
     }
   }
 
-  data class PointerData(
+  private data class PointerData(
     val pointerId: Int,
     var x: Float,
     var y: Float,
diff --git a/android/src/main/java/com/swmansion/gesturehandler/react/RNGestureHandlerModule.kt b/android/src/main/java/com/swmansion/gesturehandler/react/RNGestureHandlerModule.kt
index 544e9d53bf..98199b94c6 100644
--- a/android/src/main/java/com/swmansion/gesturehandler/react/RNGestureHandlerModule.kt
+++ b/android/src/main/java/com/swmansion/gesturehandler/react/RNGestureHandlerModule.kt
@@ -433,7 +433,10 @@ class RNGestureHandlerModule(reactContext: ReactApplicationContext?) :
 
   override fun setGestureHandlerState(handlerTag: Int, newState: Int) {
     registry.getHandler(handlerTag)?.let { handler ->
+      // Try to initialize the handler in case it was not yet initialized
       handler.initialize()
+      // Try to transition to the BEGIN state (possible only from UNDETERMINED)
+      // to force the correct event flow
       handler.begin()
 
       when (newState) {

From 785664676e7533e9d0ed06ca4d97c53302e1e198 Mon Sep 17 00:00:00 2001
From: Jakub Piasecki <jakub.piasecki@swmansion.com>
Date: Wed, 19 Oct 2022 16:23:31 +0200
Subject: [PATCH 3/3] Add comment

---
 .../gesturehandler/core/GestureHandler.kt     | 24 ++++++++++---------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/android/src/main/java/com/swmansion/gesturehandler/core/GestureHandler.kt b/android/src/main/java/com/swmansion/gesturehandler/core/GestureHandler.kt
index bc020c1ebe..973dd23cb2 100644
--- a/android/src/main/java/com/swmansion/gesturehandler/core/GestureHandler.kt
+++ b/android/src/main/java/com/swmansion/gesturehandler/core/GestureHandler.kt
@@ -69,6 +69,8 @@ open class GestureHandler<ConcreteGestureHandlerT : GestureHandler<ConcreteGestu
   private var onTouchEventListener: OnTouchEventListener? = null
   private var interactionController: GestureHandlerInteractionController? = null
 
+  // a field to store a motion event that caused the touch event to be dispatched, in case the state
+  // change is triggered in the callback, this event will be used to initialize the gesture
   private var eventTriggeringStateChangeInTouchEventHandler: MotionEvent? = null
 
   @Suppress("UNCHECKED_CAST")
@@ -461,17 +463,17 @@ open class GestureHandler<ConcreteGestureHandlerT : GestureHandler<ConcreteGestu
     eventTriggeringStateChangeInTouchEventHandler = sourceEvent
 
     when (event.actionMasked) {
-        MotionEvent.ACTION_DOWN, MotionEvent.ACTION_POINTER_DOWN -> {
-          handleTouchDownEvent(event)
-          handleTouchMoveEvent(event)
-        }
-        MotionEvent.ACTION_UP, MotionEvent.ACTION_POINTER_UP -> {
-          handleTouchMoveEvent(event)
-          handleTouchUpEvent(event)
-        }
-        MotionEvent.ACTION_MOVE -> {
-          handleTouchMoveEvent(event)
-        }
+      MotionEvent.ACTION_DOWN, MotionEvent.ACTION_POINTER_DOWN -> {
+        handleTouchDownEvent(event)
+        handleTouchMoveEvent(event)
+      }
+      MotionEvent.ACTION_UP, MotionEvent.ACTION_POINTER_UP -> {
+        handleTouchMoveEvent(event)
+        handleTouchUpEvent(event)
+      }
+      MotionEvent.ACTION_MOVE -> {
+        handleTouchMoveEvent(event)
+      }
     }
 
     eventTriggeringStateChangeInTouchEventHandler = null