Fix pages downsampling

app/src/main/kotlin/org/koitharu/kotatsu/core/ui/list/lifecycle/PagerLifecycleDispatcher.kt

@@ -1,5 +1,6 @@
 package org.koitharu.kotatsu.core.ui.list.lifecycle
 
+import android.view.View
 import androidx.core.view.children
 import androidx.viewpager2.widget.ViewPager2
 import org.koitharu.kotatsu.core.util.ext.recyclerView
@@ -8,16 +9,59 @@ class PagerLifecycleDispatcher(
 	private val pager: ViewPager2,
 ) : ViewPager2.OnPageChangeCallback() {
 
+	private var pendingUpdate: OneShotLayoutListener? = null
+
 	override fun onPageSelected(position: Int) {
-		super.onPageSelected(position)
-		val rv = pager.recyclerView ?: return
-		for (child in rv.children) {
-			val wh = rv.getChildViewHolder(child) ?: continue
-			(wh as? LifecycleAwareViewHolder)?.setIsCurrent(wh.absoluteAdapterPosition == position)
-		}
+		setResumedPage(position)
 	}
 
 	fun invalidate() {
-		onPageSelected(pager.currentItem)
+		setResumedPage(pager.currentItem)
+	}
+
+	private fun setResumedPage(position: Int) {
+		pendingUpdate?.cancel()
+		pendingUpdate = null
+		var hasResumedItem = false
+		val rv = pager.recyclerView ?: return
+		if (rv.childCount == 0) {
+			return
+		}
+		for (child in rv.children) {
+			val wh = rv.getChildViewHolder(child) ?: continue
+			val isCurrent = wh.absoluteAdapterPosition == position
+			(wh as? LifecycleAwareViewHolder)?.setIsCurrent(isCurrent)
+			if (isCurrent) {
+				hasResumedItem = true
+			}
+		}
+		if (!hasResumedItem) {
+			rv.addOnLayoutChangeListener(OneShotLayoutListener(rv, position).also { pendingUpdate = it })
+		}
+	}
+
+	private inner class OneShotLayoutListener(
+		private val view: View,
+		private val targetPosition: Int,
+	) : View.OnLayoutChangeListener {
+
+		override fun onLayoutChange(
+			v: View?,
+			left: Int,
+			top: Int,
+			right: Int,
+			bottom: Int,
+			oldLeft: Int,
+			oldTop: Int,
+			oldRight: Int,
+			oldBottom: Int
+		) {
+			view.removeOnLayoutChangeListener(this)
+			setResumedPage(targetPosition)
+		}
+
+		fun cancel() {
+			view.removeOnLayoutChangeListener(this)
+		}
 	}
 }

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

@@ -5,6 +5,7 @@ import androidx.annotation.CallSuper
 import androidx.lifecycle.LifecycleOwner
 import androidx.viewbinding.ViewBinding
 import com.davemorrissey.labs.subscaleview.SubsamplingScaleImageView
+import org.koitharu.kotatsu.BuildConfig
 import org.koitharu.kotatsu.core.exceptions.resolve.ExceptionResolver
 import org.koitharu.kotatsu.core.os.NetworkState
 import org.koitharu.kotatsu.core.ui.list.lifecycle.LifecycleAwareViewHolder
@@ -81,6 +82,7 @@ abstract class BasePageHolder<B : ViewBinding>(
 	protected fun SubsamplingScaleImageView.applyDownSampling(isForeground: Boolean) {
 		downSampling = when {
 			isForeground || !settings.isReaderOptimizationEnabled -> 1
+			BuildConfig.DEBUG -> 32
 			context.isLowRamDevice() -> 8
 			else -> 4
 		}