Fix webtoon under scale

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

@@ -12,7 +12,7 @@ class WebtoonFrameLayout @JvmOverloads constructor(
 	@AttrRes defStyleAttr: Int = 0,
 ) : FrameLayout(context, attrs, defStyleAttr) {
 
-	private val target by lazy(LazyThreadSafetyMode.NONE) {
+	val target by lazy(LazyThreadSafetyMode.NONE) {
 		findViewById<WebtoonImageView>(R.id.ssiv)
 	}
 
@@ -24,4 +24,4 @@ class WebtoonFrameLayout @JvmOverloads constructor(
 		target.scrollBy(dy)
 		return target.getScroll() - oldScroll
 	}
-}
+}

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

@@ -88,6 +88,18 @@ class WebtoonImageView @JvmOverloads constructor(
 		setMeasuredDimension(width, height)
 	}
 
+	override fun onSizeChanged(w: Int, h: Int, oldw: Int, oldh: Int) {
+		super.onSizeChanged(w, h, oldw, oldh)
+		if (oldh == h || oldw == 0 || oldh == 0 || scrollRange == SCROLL_UNKNOWN) return
+
+		computeScrollRange()
+		val container = parents.firstNotNullOfOrNull { it as? WebtoonFrameLayout } ?: return
+		val parentHeight = parentHeight()
+		if (scrollPos != 0 && container.bottom < parentHeight) {
+			scrollTo(scrollRange)
+		}
+	}
+
 	private fun scrollToInternal(pos: Int) {
 		scrollPos = pos
 		ct.set(sWidth / 2f, (height / 2f + pos.toFloat()) / minScale)

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

@@ -3,6 +3,7 @@ package org.koitharu.kotatsu.reader.ui.pager.webtoon
 import android.content.Context
 import android.util.AttributeSet
 import androidx.core.view.ViewCompat.TYPE_TOUCH
+import androidx.core.view.forEach
 import androidx.recyclerview.widget.RecyclerView
 import org.koitharu.kotatsu.core.util.ext.findCenterViewPosition
 import java.util.LinkedList
@@ -13,6 +14,13 @@ class WebtoonRecyclerView @JvmOverloads constructor(
 
 	private var onPageScrollListeners: MutableList<OnPageScrollListener>? = null
 
+	override fun onMeasure(widthSpec: Int, heightSpec: Int) {
+		super.onMeasure(widthSpec, heightSpec)
+		forEach { child ->
+			(child as WebtoonFrameLayout).target.requestLayout()
+		}
+	}
+
 	override fun startNestedScroll(axes: Int) = startNestedScroll(axes, TYPE_TOUCH)
 
 	override fun startNestedScroll(axes: Int, type: Int): Boolean = true

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

@@ -1,6 +1,6 @@
 package org.koitharu.kotatsu.reader.ui.pager.webtoon
 
-import android.animation.ObjectAnimator
+import android.animation.ValueAnimator
 import android.content.Context
 import android.graphics.Matrix
 import android.graphics.Rect
@@ -15,7 +15,7 @@ import android.widget.OverScroller
 import androidx.core.view.GestureDetectorCompat
 
 private const val MAX_SCALE = 2.5f
-private const val MIN_SCALE = 1f // under-scaling disabled due to buggy nested scroll
+private const val MIN_SCALE = 0.5f
 
 class WebtoonScalingFrame @JvmOverloads constructor(
 	context: Context,
@@ -40,7 +40,6 @@ class WebtoonScalingFrame @JvmOverloads constructor(
 	private var halfHeight = 0f
 	private val translateBounds = RectF()
 	private val targetHitRect = Rect()
-	private var pendingScroll = 0
 
 	var isZoomEnable = true
 		set(value) {
@@ -101,8 +100,6 @@ class WebtoonScalingFrame @JvmOverloads constructor(
 
 		if (scale < 1) {
 			targetChild.getHitRect(targetHitRect)
-			targetChild.scrollBy(0, pendingScroll)
-			pendingScroll = 0
 		}
 	}
 
@@ -124,7 +121,6 @@ class WebtoonScalingFrame @JvmOverloads constructor(
 			else -> 0f
 		}
 
-		pendingScroll = dy.toInt()
 		transformMatrix.postTranslate(dx, dy)
 		syncMatrixValues()
 	}
@@ -159,9 +155,7 @@ class WebtoonScalingFrame @JvmOverloads constructor(
 
 	override fun onScaleBegin(detector: ScaleGestureDetector): Boolean = true
 
-	override fun onScaleEnd(p0: ScaleGestureDetector) {
-		pendingScroll = 0
-	}
+	override fun onScaleEnd(p0: ScaleGestureDetector) = Unit
 
 
 	private inner class GestureListener : GestureDetector.SimpleOnGestureListener(), Runnable {
@@ -175,7 +169,7 @@ class WebtoonScalingFrame @JvmOverloads constructor(
 
 		override fun onDoubleTap(e: MotionEvent): Boolean {
 			val newScale = if (scale != 1f) 1f else MAX_SCALE * 0.8f
-			ObjectAnimator.ofFloat(scale, newScale).run {
+			ValueAnimator.ofFloat(scale, newScale).run {
 				interpolator = AccelerateDecelerateInterpolator()
 				duration = 300
 				addUpdateListener {