Avoid unnecessary child layout in webtoon recycler

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

@@ -2,6 +2,7 @@ package org.koitharu.kotatsu.reader.ui.pager.webtoon
 
 import android.content.Context
 import android.util.AttributeSet
+import android.view.View
 import androidx.core.view.ViewCompat.TYPE_TOUCH
 import androidx.core.view.forEach
 import androidx.recyclerview.widget.RecyclerView
@@ -13,12 +14,16 @@ class WebtoonRecyclerView @JvmOverloads constructor(
 ) : RecyclerView(context, attrs, defStyleAttr) {
 
 	private var onPageScrollListeners: MutableList<OnPageScrollListener>? = null
+	private val detachedViews = ArrayList<View>()
 
-	override fun onMeasure(widthSpec: Int, heightSpec: Int) {
-		super.onMeasure(widthSpec, heightSpec)
-		forEach { child ->
-			(child as WebtoonFrameLayout).target.requestLayout()
-		}
+	override fun onChildDetachedFromWindow(child: View) {
+		super.onChildDetachedFromWindow(child)
+		detachedViews.add(child)
+	}
+
+	override fun onChildAttachedToWindow(child: View) {
+		super.onChildAttachedToWindow(child)
+		detachedViews.remove(child)
 	}
 
 	override fun startNestedScroll(axes: Int) = startNestedScroll(axes, TYPE_TOUCH)
@@ -106,6 +111,15 @@ class WebtoonRecyclerView @JvmOverloads constructor(
 		listeners.forEach { it.dispatchScroll(this, dy, centerPosition) }
 	}
 
+	fun relayoutChildren() {
+		forEach { child ->
+			(child as WebtoonFrameLayout).target.requestLayout()
+		}
+		detachedViews.forEach {child ->
+			(child as WebtoonFrameLayout).target.requestLayout()
+		}
+	}
+
 	abstract class OnPageScrollListener {
 
 		private var lastPosition = NO_POSITION

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

@@ -23,7 +23,7 @@ class WebtoonScalingFrame @JvmOverloads constructor(
 	defStyles: Int = 0,
 ) : FrameLayout(context, attrs, defStyles), ScaleGestureDetector.OnScaleGestureListener {
 
-	private val targetChild by lazy(LazyThreadSafetyMode.NONE) { getChildAt(0) }
+	private val targetChild by lazy(LazyThreadSafetyMode.NONE) { getChildAt(0) as WebtoonRecyclerView }
 
 	private val scaleDetector = ScaleGestureDetector(context, this)
 	private val gestureDetector = GestureDetectorCompat(context, GestureListener())
@@ -96,6 +96,7 @@ class WebtoonScalingFrame @JvmOverloads constructor(
 		if (newHeight != targetChild.height) {
 			targetChild.layoutParams.height = newHeight
 			targetChild.requestLayout()
+			targetChild.relayoutChildren()
 		}
 
 		if (scale < 1) {