Make base GestureHandler on Android non generic (#3491)

## Description

Depends on
#3489

On Android, `GestureHandler` was a generic class specialized by the
concrete type of the handler. The only place it was used was `applySelf`
method, which allowed for inherited methods to return the concrete
handler:

```
tapHandler.setEnabled(true) // returns TapGestureHandler instead of GestureHandler
```

...but we don't use this pattern anywhere. It made much more sense in
Java, than it does in Kotlin, where we can simply use `apply`, `let`,
etc. when there's a need to do multiple operations on the same object.
Now, it simply makes the logic dealing with gesture handlers more
complicated as it also needs to keep track of the generic type, which in
most cases is `*` so it doesn't give us more type safety.

This PR makes it so that the base `GestureHandler` class is no longer
generic, which should make life easier when dealing with non-concrete
gesture handlers in the future.

## Test plan

Build example apps

Author: j-piasecki

packages/react-native-gesture-handler/android/src/main/java/com/swmansion/gesturehandler/core/FlingGestureHandler.kt

@@ -8,7 +8,7 @@ import android.view.VelocityTracker
 import com.facebook.react.bridge.ReadableMap
 import com.swmansion.gesturehandler.react.eventbuilders.FlingGestureHandlerEventDataBuilder
 
-class FlingGestureHandler : GestureHandler<FlingGestureHandler>() {
+class FlingGestureHandler : GestureHandler() {
   var numberOfPointersRequired = DEFAULT_NUMBER_OF_TOUCHES_REQUIRED
   var direction = DEFAULT_DIRECTION
 

packages/react-native-gesture-handler/android/src/main/java/com/swmansion/gesturehandler/core/GestureHandler.kt

@@ -23,7 +23,7 @@ import com.swmansion.gesturehandler.react.eventbuilders.GestureHandlerEventDataB
 import java.lang.IllegalStateException
 import java.util.*
 
-open class GestureHandler<ConcreteGestureHandlerT : GestureHandler<ConcreteGestureHandlerT>> {
+open class GestureHandler {
   private val trackedPointerIDs = IntArray(MAX_POINTERS_COUNT)
   private var trackedPointersIDsCount = 0
   private val windowOffset = IntArray(2) { 0 }
@@ -79,37 +79,30 @@ open class GestureHandler<ConcreteGestureHandlerT : GestureHandler<ConcreteGestu
     protected set
   protected var shouldCancelWhenOutside = false
   protected var orchestrator: GestureHandlerOrchestrator? = null
-  private var onTouchEventListener: OnTouchEventListener? = null
+  var onTouchEventListener: OnTouchEventListener? = null
   private var interactionController: GestureHandlerInteractionController? = null
   var pointerType: Int = POINTER_TYPE_OTHER
     private set
 
   protected var mouseButton = 0
 
-  @Suppress("UNCHECKED_CAST")
-  protected fun self(): ConcreteGestureHandlerT = this as ConcreteGestureHandlerT
-
-  protected inline fun applySelf(block: ConcreteGestureHandlerT.() -> Unit): ConcreteGestureHandlerT = self().apply {
-    block()
-  }
-
   // properties set and accessed only by the orchestrator
   var activationIndex = 0
   var isActive = false
   var isAwaiting = false
   var shouldResetProgress = false
 
   open fun dispatchStateChange(newState: Int, prevState: Int) {
-    onTouchEventListener?.onStateChange(self(), newState, prevState)
+    onTouchEventListener?.onStateChange(this, newState, prevState)
   }
 
   open fun dispatchHandlerUpdate(event: MotionEvent) {
-    onTouchEventListener?.onHandlerUpdate(self(), event)
+    onTouchEventListener?.onHandlerUpdate(this, event)
   }
 
   open fun dispatchTouchEvent() {
     if (changedTouchesPayload != null) {
-      onTouchEventListener?.onTouchEvent(self())
+      onTouchEventListener?.onTouchEvent(this)
     }
   }
 
@@ -122,7 +115,7 @@ open class GestureHandler<ConcreteGestureHandlerT : GestureHandler<ConcreteGestu
     mouseButton = DEFAULT_MOUSE_BUTTON
   }
 
-  fun hasCommonPointers(other: GestureHandler<*>): Boolean {
+  fun hasCommonPointers(other: GestureHandler): Boolean {
     for (i in trackedPointerIDs.indices) {
       if (trackedPointerIDs[i] != -1 && other.trackedPointerIDs[i] != -1) {
         return true
@@ -131,14 +124,7 @@ open class GestureHandler<ConcreteGestureHandlerT : GestureHandler<ConcreteGestu
     return false
   }
 
-  fun setHitSlop(
-    leftPad: Float,
-    topPad: Float,
-    rightPad: Float,
-    bottomPad: Float,
-    width: Float,
-    height: Float,
-  ): ConcreteGestureHandlerT = applySelf {
+  fun setHitSlop(leftPad: Float, topPad: Float, rightPad: Float, bottomPad: Float, width: Float, height: Float) {
     if (hitSlop == null) {
       hitSlop = FloatArray(6)
     }
@@ -162,10 +148,9 @@ open class GestureHandler<ConcreteGestureHandlerT : GestureHandler<ConcreteGestu
     }
   }
 
-  fun setHitSlop(padding: Float): ConcreteGestureHandlerT =
-    setHitSlop(padding, padding, padding, padding, HIT_SLOP_NONE, HIT_SLOP_NONE)
+  fun setHitSlop(padding: Float) = setHitSlop(padding, padding, padding, padding, HIT_SLOP_NONE, HIT_SLOP_NONE)
 
-  fun setInteractionController(controller: GestureHandlerInteractionController?): ConcreteGestureHandlerT = applySelf {
+  fun setInteractionController(controller: GestureHandlerInteractionController?) {
     interactionController = controller
   }
 
@@ -331,7 +316,7 @@ open class GestureHandler<ConcreteGestureHandlerT : GestureHandler<ConcreteGestu
   }
 
   // exception to help debug https://github.com/software-mansion/react-native-gesture-handler/issues/1188
-  class AdaptEventException(handler: GestureHandler<*>, event: MotionEvent, e: IllegalArgumentException) :
+  class AdaptEventException(handler: GestureHandler, event: MotionEvent, e: IllegalArgumentException) :
     Exception(
       """
     handler: ${handler::class.simpleName}
@@ -594,31 +579,31 @@ open class GestureHandler<ConcreteGestureHandlerT : GestureHandler<ConcreteGestu
     state != STATE_END &&
     trackedPointersIDsCount > 0
 
-  open fun shouldRequireToWaitForFailure(handler: GestureHandler<*>): Boolean {
+  open fun shouldRequireToWaitForFailure(handler: GestureHandler): Boolean {
     if (handler === this) {
       return false
     }
 
     return interactionController?.shouldRequireHandlerToWaitForFailure(this, handler) ?: false
   }
 
-  fun shouldWaitForHandlerFailure(handler: GestureHandler<*>): Boolean {
+  fun shouldWaitForHandlerFailure(handler: GestureHandler): Boolean {
     if (handler === this) {
       return false
     }
 
     return interactionController?.shouldWaitForHandlerFailure(this, handler) ?: false
   }
 
-  open fun shouldRecognizeSimultaneously(handler: GestureHandler<*>): Boolean {
+  open fun shouldRecognizeSimultaneously(handler: GestureHandler): Boolean {
     if (handler === this) {
       return true
     }
 
     return interactionController?.shouldRecognizeSimultaneously(this, handler) ?: false
   }
 
-  open fun shouldBeCancelledBy(handler: GestureHandler<*>): Boolean {
+  open fun shouldBeCancelledBy(handler: GestureHandler): Boolean {
     if (handler === this) {
       return false
     }
@@ -714,7 +699,7 @@ open class GestureHandler<ConcreteGestureHandlerT : GestureHandler<ConcreteGestu
    * Returns true if the view this handler is attached to is a descendant of the view the other handler
    * is attached to and false otherwise.
    */
-  fun isDescendantOf(of: GestureHandler<*>): Boolean {
+  fun isDescendantOf(of: GestureHandler): Boolean {
     var view = this.view?.parent as? View
     while (view != null) {
       if (view == of.view) {
@@ -831,11 +816,6 @@ open class GestureHandler<ConcreteGestureHandlerT : GestureHandler<ConcreteGestu
     }
   }
 
-  fun setOnTouchEventListener(listener: OnTouchEventListener?): GestureHandler<*> {
-    onTouchEventListener = listener
-    return this
-  }
-
   override fun toString(): String {
     val viewString = if (view == null) null else view!!.javaClass.simpleName
     return this.javaClass.simpleName + "@[" + tag + "]:" + viewString
@@ -851,7 +831,7 @@ open class GestureHandler<ConcreteGestureHandlerT : GestureHandler<ConcreteGestu
   val lastPositionInWindowY: Float
     get() = lastAbsolutePositionY + lastEventOffsetY - windowOffset[1]
 
-  abstract class Factory<T : GestureHandler<T>> {
+  abstract class Factory<T : GestureHandler> {
     abstract val type: Class<T>
     abstract val name: String
 
@@ -899,7 +879,7 @@ open class GestureHandler<ConcreteGestureHandlerT : GestureHandler<ConcreteGestu
       private const val KEY_HIT_SLOP_WIDTH = "width"
       private const val KEY_HIT_SLOP_HEIGHT = "height"
 
-      private fun handleHitSlopProperty(handler: GestureHandler<*>, config: ReadableMap) {
+      private fun handleHitSlopProperty(handler: GestureHandler, config: ReadableMap) {
         if (config.getType(KEY_HIT_SLOP) == ReadableType.Number) {
           val hitSlop = PixelUtil.toPixelFromDIP(config.getDouble(KEY_HIT_SLOP))
           handler.setHitSlop(

packages/react-native-gesture-handler/android/src/main/java/com/swmansion/gesturehandler/core/GestureHandlerInteractionController.kt

@@ -1,8 +1,8 @@
 package com.swmansion.gesturehandler.core
 
 interface GestureHandlerInteractionController {
-  fun shouldWaitForHandlerFailure(handler: GestureHandler<*>, otherHandler: GestureHandler<*>): Boolean
-  fun shouldRequireHandlerToWaitForFailure(handler: GestureHandler<*>, otherHandler: GestureHandler<*>): Boolean
-  fun shouldRecognizeSimultaneously(handler: GestureHandler<*>, otherHandler: GestureHandler<*>): Boolean
-  fun shouldHandlerBeCancelledBy(handler: GestureHandler<*>, otherHandler: GestureHandler<*>): Boolean
+  fun shouldWaitForHandlerFailure(handler: GestureHandler, otherHandler: GestureHandler): Boolean
+  fun shouldRequireHandlerToWaitForFailure(handler: GestureHandler, otherHandler: GestureHandler): Boolean
+  fun shouldRecognizeSimultaneously(handler: GestureHandler, otherHandler: GestureHandler): Boolean
+  fun shouldHandlerBeCancelledBy(handler: GestureHandler, otherHandler: GestureHandler): Boolean
 }

packages/react-native-gesture-handler/android/src/main/java/com/swmansion/gesturehandler/core/GestureHandlerOrchestrator.kt

@@ -20,9 +20,9 @@ class GestureHandlerOrchestrator(
    * traversing view hierarchy and looking for gesture handlers.
    */
   var minimumAlphaForTraversal = DEFAULT_MIN_ALPHA_FOR_TRAVERSAL
-  private val gestureHandlers = arrayListOf<GestureHandler<*>>()
-  private val awaitingHandlers = arrayListOf<GestureHandler<*>>()
-  private val preparedHandlers = arrayListOf<GestureHandler<*>>()
+  private val gestureHandlers = arrayListOf<GestureHandler>()
+  private val awaitingHandlers = arrayListOf<GestureHandler>()
+  private val preparedHandlers = arrayListOf<GestureHandler>()
 
   // In `onHandlerStateChange` method we iterate through `awaitingHandlers`, but calling `tryActivate` may modify this list.
   // To avoid `ConcurrentModificationException` we iterate through copy. There is one more problem though - if handler was
@@ -85,22 +85,20 @@ class GestureHandlerOrchestrator(
     finishedHandlersCleanupScheduled = false
   }
 
-  private fun hasOtherHandlerToWaitFor(handler: GestureHandler<*>) = gestureHandlers.any {
-    !isFinished(it.state) && shouldHandlerWaitForOther(handler, it)
-  }
+  private fun hasOtherHandlerToWaitFor(handler: GestureHandler) =
+    gestureHandlers.any { !isFinished(it.state) && shouldHandlerWaitForOther(handler, it) }
 
-  private fun shouldBeCancelledByFinishedHandler(handler: GestureHandler<*>) = gestureHandlers.any {
-    shouldHandlerWaitForOther(handler, it) && it.state == GestureHandler.STATE_END
-  }
+  private fun shouldBeCancelledByFinishedHandler(handler: GestureHandler) =
+    gestureHandlers.any { shouldHandlerWaitForOther(handler, it) && it.state == GestureHandler.STATE_END }
 
-  private fun shouldBeCancelledByActiveHandler(handler: GestureHandler<*>) = gestureHandlers.any {
+  private fun shouldBeCancelledByActiveHandler(handler: GestureHandler) = gestureHandlers.any {
     handler.hasCommonPointers(it) &&
       it.state == GestureHandler.STATE_ACTIVE &&
       !canRunSimultaneously(handler, it) &&
       handler.isDescendantOf(it)
   }
 
-  private fun tryActivate(handler: GestureHandler<*>) {
+  private fun tryActivate(handler: GestureHandler) {
     // If we are waiting for a gesture that has successfully finished, we should cancel handler
     if (shouldBeCancelledByFinishedHandler(handler) || shouldBeCancelledByActiveHandler(handler)) {
       handler.cancel()
@@ -129,7 +127,7 @@ class GestureHandlerOrchestrator(
   }
 
   /*package*/
-  fun onHandlerStateChange(handler: GestureHandler<*>, newState: Int, prevState: Int) {
+  fun onHandlerStateChange(handler: GestureHandler, newState: Int, prevState: Int) {
     handlingChangeSemaphore += 1
     if (isFinished(newState)) {
       // We have to loop through copy in order to avoid modifying collection
@@ -193,7 +191,7 @@ class GestureHandlerOrchestrator(
     scheduleFinishedHandlersCleanup()
   }
 
-  private fun makeActive(handler: GestureHandler<*>) {
+  private fun makeActive(handler: GestureHandler) {
     val currentState = handler.state
     with(handler) {
       isAwaiting = false
@@ -270,7 +268,7 @@ class GestureHandlerOrchestrator(
     }
   }
 
-  private fun deliverEventToGestureHandler(handler: GestureHandler<*>, sourceEvent: MotionEvent) {
+  private fun deliverEventToGestureHandler(handler: GestureHandler, sourceEvent: MotionEvent) {
     if (!isViewAttachedUnderWrapper(handler.view)) {
       handler.cancel()
       return
@@ -424,7 +422,7 @@ class GestureHandlerOrchestrator(
     return point
   }
 
-  private fun addAwaitingHandler(handler: GestureHandler<*>) {
+  private fun addAwaitingHandler(handler: GestureHandler) {
     if (awaitingHandlers.contains(handler)) {
       return
     }
@@ -438,7 +436,7 @@ class GestureHandlerOrchestrator(
     }
   }
 
-  private fun recordHandlerIfNotPresent(handler: GestureHandler<*>, view: View) {
+  private fun recordHandlerIfNotPresent(handler: GestureHandler, view: View) {
     if (gestureHandlers.contains(handler)) {
       return
     }
@@ -497,7 +495,7 @@ class GestureHandlerOrchestrator(
   // There's only one exception - RootViewGestureHandler. TalkBack uses hover events,
   // so we need to pass them into RootViewGestureHandler, otherwise press and hold
   // gesture stops working correctly (see https://github.com/software-mansion/react-native-gesture-handler/issues/3407)
-  private fun shouldHandlerSkipHoverEvents(handler: GestureHandler<*>, action: Int): Boolean {
+  private fun shouldHandlerSkipHoverEvents(handler: GestureHandler, action: Int): Boolean {
     val shouldSkipHoverEvents =
       handler !is HoverGestureHandler &&
         handler !is RNGestureHandlerRootHelper.RootViewGestureHandler
@@ -672,7 +670,7 @@ class GestureHandlerOrchestrator(
     private val matrixTransformCoords = FloatArray(2)
     private val inverseMatrix = Matrix()
     private val tempCoords = FloatArray(2)
-    private val handlersComparator = Comparator<GestureHandler<*>> { a, b ->
+    private val handlersComparator = Comparator<GestureHandler> { a, b ->
       return@Comparator if (a.isActive && b.isActive || a.isAwaiting && b.isAwaiting) {
         // both A and B are either active or awaiting activation, in which case we prefer one that
         // has activated (or turned into "awaiting" state) earlier
@@ -726,17 +724,16 @@ class GestureHandlerOrchestrator(
     private fun isTransformedTouchPointInView(x: Float, y: Float, child: View) =
       x in 0f..child.width.toFloat() && y in 0f..child.height.toFloat()
 
-    private fun shouldHandlerWaitForOther(handler: GestureHandler<*>, other: GestureHandler<*>): Boolean =
-      handler !== other &&
-        (
-          handler.shouldWaitForHandlerFailure(other) ||
-            other.shouldRequireToWaitForFailure(handler)
-          )
+    private fun shouldHandlerWaitForOther(handler: GestureHandler, other: GestureHandler): Boolean =
+      handler !== other && (
+        handler.shouldWaitForHandlerFailure(other) ||
+          other.shouldRequireToWaitForFailure(handler)
+        )
 
-    private fun canRunSimultaneously(a: GestureHandler<*>, b: GestureHandler<*>) =
+    private fun canRunSimultaneously(a: GestureHandler, b: GestureHandler) =
       a === b || a.shouldRecognizeSimultaneously(b) || b.shouldRecognizeSimultaneously(a)
 
-    private fun shouldHandlerBeCancelledBy(handler: GestureHandler<*>, other: GestureHandler<*>): Boolean {
+    private fun shouldHandlerBeCancelledBy(handler: GestureHandler, other: GestureHandler): Boolean {
       if (!handler.hasCommonPointers(other)) {
         // if two handlers share no common pointer one can never trigger cancel for the other
         return false

packages/react-native-gesture-handler/android/src/main/java/com/swmansion/gesturehandler/core/GestureHandlerRegistry.kt

@@ -4,5 +4,5 @@ import android.view.View
 import java.util.*
 
 interface GestureHandlerRegistry {
-  fun getHandlersForView(view: View): ArrayList<GestureHandler<*>>?
+  fun getHandlersForView(view: View): ArrayList<GestureHandler>?
 }

packages/react-native-gesture-handler/android/src/main/java/com/swmansion/gesturehandler/core/HoverGestureHandler.kt

@@ -10,13 +10,13 @@ import com.swmansion.gesturehandler.react.RNGestureHandlerRootHelper
 import com.swmansion.gesturehandler.react.RNViewConfigurationHelper
 import com.swmansion.gesturehandler.react.eventbuilders.HoverGestureHandlerEventDataBuilder
 
-class HoverGestureHandler : GestureHandler<HoverGestureHandler>() {
+class HoverGestureHandler : GestureHandler() {
   private var handler: Handler? = null
   private var finishRunnable = Runnable { finish() }
   var stylusData: StylusData = StylusData()
     private set
 
-  private infix fun isAncestorOf(other: GestureHandler<*>): Boolean {
+  private infix fun isAncestorOf(other: GestureHandler): Boolean {
     var current: View? = other.view
 
     while (current != null) {
@@ -50,15 +50,15 @@ class HoverGestureHandler : GestureHandler<HoverGestureHandler>() {
     return null
   }
 
-  override fun shouldBeCancelledBy(handler: GestureHandler<*>): Boolean {
+  override fun shouldBeCancelledBy(handler: GestureHandler): Boolean {
     if (handler is HoverGestureHandler && !(handler isAncestorOf this)) {
       return isViewDisplayedOverAnother(handler.view!!, this.view!!)!!
     }
 
     return super.shouldBeCancelledBy(handler)
   }
 
-  override fun shouldRequireToWaitForFailure(handler: GestureHandler<*>): Boolean {
+  override fun shouldRequireToWaitForFailure(handler: GestureHandler): Boolean {
     if (handler is HoverGestureHandler) {
       if (!(this isAncestorOf handler) && !(handler isAncestorOf this)) {
         isViewDisplayedOverAnother(this.view!!, handler.view!!)?.let {
@@ -70,10 +70,8 @@ class HoverGestureHandler : GestureHandler<HoverGestureHandler>() {
     return super.shouldRequireToWaitForFailure(handler)
   }
 
-  override fun shouldRecognizeSimultaneously(handler: GestureHandler<*>): Boolean {
-    if (handler is HoverGestureHandler &&
-      (this isAncestorOf handler || handler isAncestorOf this)
-    ) {
+  override fun shouldRecognizeSimultaneously(handler: GestureHandler): Boolean {
+    if (handler is HoverGestureHandler && (this isAncestorOf handler || handler isAncestorOf this)) {
       return true
     }
 

packages/react-native-gesture-handler/android/src/main/java/com/swmansion/gesturehandler/core/LongPressGestureHandler.kt

@@ -9,7 +9,7 @@ import com.facebook.react.bridge.ReadableMap
 import com.facebook.react.uimanager.PixelUtil
 import com.swmansion.gesturehandler.react.eventbuilders.LongPressGestureHandlerEventDataBuilder
 
-class LongPressGestureHandler(context: Context) : GestureHandler<LongPressGestureHandler>() {
+class LongPressGestureHandler(context: Context) : GestureHandler() {
   var minDurationMs = DEFAULT_MIN_DURATION_MS
   val duration: Int
     get() = (previousTime - startTime).toInt()

packages/react-native-gesture-handler/android/src/main/java/com/swmansion/gesturehandler/core/ManualGestureHandler.kt

@@ -4,7 +4,7 @@ import android.content.Context
 import android.view.MotionEvent
 import com.swmansion.gesturehandler.react.eventbuilders.ManualGestureHandlerEventDataBuilder
 
-class ManualGestureHandler : GestureHandler<ManualGestureHandler>() {
+class ManualGestureHandler : GestureHandler() {
   override fun onHandle(event: MotionEvent, sourceEvent: MotionEvent) {
     if (state == STATE_UNDETERMINED) {
       begin()