Improve webtoon zoom fling

app/src/main/kotlin/org/koitharu/kotatsu/reader/ui/pager/webtoon/WebtoonScalingFrame.kt

@@ -3,6 +3,7 @@ package org.koitharu.kotatsu.reader.ui.pager.webtoon
 import android.animation.ValueAnimator
 import android.content.Context
 import android.graphics.Matrix
+import android.graphics.Point
 import android.graphics.Rect
 import android.graphics.RectF
 import android.util.AttributeSet
@@ -19,12 +20,16 @@ import android.widget.OverScroller
 import androidx.core.animation.doOnEnd
 import androidx.core.view.GestureDetectorCompat
 import androidx.core.view.ViewConfigurationCompat
+import org.koitharu.kotatsu.R
 import org.koitharu.kotatsu.core.ui.widgets.ZoomControl
 import org.koitharu.kotatsu.core.util.ext.getAnimationDuration
+import kotlin.math.roundToInt
 
 private const val MAX_SCALE = 2.5f
 private const val MIN_SCALE = 0.5f
 
+private const val FLING_RANGE = 20_000
+
 class WebtoonScalingFrame @JvmOverloads constructor(
 	context: Context,
 	attrs: AttributeSet? = null,
@@ -36,6 +41,7 @@ class WebtoonScalingFrame @JvmOverloads constructor(
 	private val scaleDetector = ScaleGestureDetector(context, this)
 	private val gestureDetector = GestureDetectorCompat(context, GestureListener())
 	private val overScroller = OverScroller(context, AccelerateDecelerateInterpolator())
+
 	private val transformMatrix = Matrix()
 	private val matrixValues = FloatArray(9)
 	private val scale
@@ -49,6 +55,7 @@ class WebtoonScalingFrame @JvmOverloads constructor(
 	private val translateBounds = RectF()
 	private val targetHitRect = Rect()
 	private var animator: ValueAnimator? = null
+	private var pendingScroll = 0
 
 	var isZoomEnable = false
 		set(value) {
@@ -80,7 +87,7 @@ class WebtoonScalingFrame @JvmOverloads constructor(
 			overScroller.forceFinished(true)
 		}
 
-		gestureDetector.onTouchEvent(ev)
+		val consumed = gestureDetector.onTouchEvent(ev)
 		scaleDetector.onTouchEvent(ev)
 
 		// Offset event to inside the child view
@@ -88,11 +95,7 @@ class WebtoonScalingFrame @JvmOverloads constructor(
 			ev.offsetLocation(halfWidth - ev.x + targetHitRect.width() / 3, 0f)
 		}
 
-		// Send action cancel to avoid recycler jump when scale end
-		if (scaleDetector.isInProgress) {
-			ev.action = MotionEvent.ACTION_CANCEL
-		}
-		return super.dispatchTouchEvent(ev)
+		return consumed || scaleDetector.isInProgress || super.dispatchTouchEvent(ev)
 	}
 
 	override fun onGenericMotionEvent(event: MotionEvent): Boolean {
@@ -178,6 +181,10 @@ class WebtoonScalingFrame @JvmOverloads constructor(
 			scaleY = scale
 			translationX = transX
 			translationY = transY
+			if (pendingScroll != 0) {
+				nestedScrollBy(0, pendingScroll)
+				pendingScroll = 0
+			}
 		}
 
 		val newHeight = if (scale < 1f) (height / scale).toInt() else height
@@ -210,6 +217,7 @@ class WebtoonScalingFrame @JvmOverloads constructor(
 			else -> 0f
 		}
 
+		pendingScroll = if (scale > 1) (dy / scale).roundToInt() else 0
 		transformMatrix.postTranslate(dx, dy)
 		syncMatrixValues()
 	}
@@ -277,6 +285,7 @@ class WebtoonScalingFrame @JvmOverloads constructor(
 	private fun findTargetChild() = getChildAt(0) as WebtoonRecyclerView
 
 	private inner class GestureListener : GestureDetector.SimpleOnGestureListener(), Runnable {
+		private val prevPos = Point()
 
 		override fun onScroll(
 			e1: MotionEvent?,
@@ -294,7 +303,7 @@ class WebtoonScalingFrame @JvmOverloads constructor(
 			val newScale = if (scale != 1f) 1f else MAX_SCALE * 0.8f
 			ValueAnimator.ofFloat(scale, newScale).run {
 				interpolator = AccelerateDecelerateInterpolator()
-				duration = 300
+				duration = context.getAnimationDuration(R.integer.config_defaultAnimTime)
 				addUpdateListener {
 					scaleChild(it.animatedValue as Float, e.x, e.y)
 				}
@@ -311,15 +320,16 @@ class WebtoonScalingFrame @JvmOverloads constructor(
 		): Boolean {
 			if (scale <= 1) return false
 
+			prevPos.set(transX.toInt(), transY.toInt())
 			overScroller.fling(
-				transX.toInt(),
-				transY.toInt(),
+				prevPos.x,
+				prevPos.y,
 				velocityX.toInt(),
 				velocityY.toInt(),
 				translateBounds.left.toInt(),
 				translateBounds.right.toInt(),
-				translateBounds.top.toInt(),
-				translateBounds.bottom.toInt(),
+				translateBounds.top.toInt() - FLING_RANGE,
+				translateBounds.bottom.toInt() + FLING_RANGE,
 			)
 			postOnAnimation(this)
 			return true
@@ -328,9 +338,10 @@ class WebtoonScalingFrame @JvmOverloads constructor(
 		override fun run() {
 			if (overScroller.computeScrollOffset()) {
 				transformMatrix.postTranslate(
-					overScroller.currX - transX,
-					overScroller.currY - transY,
+					overScroller.currX.toFloat() - prevPos.x,
+					overScroller.currY.toFloat() - prevPos.y
 				)
+				prevPos.set(overScroller.currX, overScroller.currY)
 				invalidateTarget()
 				postOnAnimation(this)
 			}