Double reader integration

app/src/main/kotlin/org/koitharu/kotatsu/core/prefs/ReaderMode.kt

@@ -6,6 +6,7 @@ enum class ReaderMode(val id: Int) {
 	REVERSED(3),
 	VERTICAL(4),
 	WEBTOON(2),
+	DOUBLE(5),
 	;
 
 	companion object {

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

@@ -6,7 +6,7 @@ import androidx.fragment.app.commit
 import org.koitharu.kotatsu.R
 import org.koitharu.kotatsu.core.prefs.ReaderMode
 import org.koitharu.kotatsu.reader.ui.pager.BaseReaderFragment
-import org.koitharu.kotatsu.reader.ui.pager.doublepage.DoublePageReaderFragment
+import org.koitharu.kotatsu.reader.ui.pager.doublepage.DoubleReaderFragment
 import org.koitharu.kotatsu.reader.ui.pager.reversed.ReversedReaderFragment
 import org.koitharu.kotatsu.reader.ui.pager.standard.PagerReaderFragment
 import org.koitharu.kotatsu.reader.ui.pager.vertical.VerticalReaderFragment
@@ -23,7 +23,7 @@ class ReaderManager(
 	init {
 		val isTablet = container.resources.getBoolean(R.bool.is_tablet)
 		modeMap[ReaderMode.STANDARD] = if (isTablet) {
-			DoublePageReaderFragment::class.java
+			DoubleReaderFragment::class.java
 		} else {
 			PagerReaderFragment::class.java
 		}

app/src/main/kotlin/org/koitharu/kotatsu/reader/ui/config/ReaderConfigSheet.kt

@@ -80,6 +80,7 @@ class ReaderConfigSheet :
 		binding.buttonReversed.isChecked = mode == ReaderMode.REVERSED
 		binding.buttonWebtoon.isChecked = mode == ReaderMode.WEBTOON
 		binding.buttonVertical.isChecked = mode == ReaderMode.VERTICAL
+		binding.buttonDouble.isChecked = mode == ReaderMode.DOUBLE
 
 		binding.checkableGroup.addOnButtonCheckedListener(this)
 		binding.buttonSavePage.setOnClickListener(this)
@@ -155,6 +156,7 @@ class ReaderConfigSheet :
 			R.id.button_webtoon -> ReaderMode.WEBTOON
 			R.id.button_reversed -> ReaderMode.REVERSED
 			R.id.button_vertical -> ReaderMode.VERTICAL
+			R.id.button_double -> ReaderMode.DOUBLE
 			else -> return
 		}
 		if (newMode == mode) {

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

@@ -7,8 +7,8 @@ import androidx.recyclerview.widget.LinearLayoutManager
 import androidx.recyclerview.widget.RecyclerView
 import com.google.android.material.snackbar.Snackbar
 import dagger.hilt.android.AndroidEntryPoint
-import kotlinx.coroutines.async
 import kotlinx.coroutines.coroutineScope
+import kotlinx.coroutines.launch
 import kotlinx.coroutines.yield
 import org.koitharu.kotatsu.R
 import org.koitharu.kotatsu.core.os.NetworkState
@@ -17,14 +17,16 @@ import org.koitharu.kotatsu.databinding.FragmentReaderDoubleBinding
 import org.koitharu.kotatsu.parsers.util.toIntUp
 import org.koitharu.kotatsu.reader.domain.PageLoader
 import org.koitharu.kotatsu.reader.ui.ReaderState
+import org.koitharu.kotatsu.reader.ui.ReaderViewModel
 import org.koitharu.kotatsu.reader.ui.pager.BaseReaderAdapter
 import org.koitharu.kotatsu.reader.ui.pager.BaseReaderFragment
 import org.koitharu.kotatsu.reader.ui.pager.ReaderPage
+import org.koitharu.kotatsu.reader.ui.pager.standard.PageHolder
 import javax.inject.Inject
 import kotlin.math.absoluteValue
 
 @AndroidEntryPoint
-class DoublePageReaderFragment : BaseReaderFragment<FragmentReaderDoubleBinding>() {
+class DoubleReaderFragment : BaseReaderFragment<FragmentReaderDoubleBinding>() {
 
 	@Inject
 	lateinit var networkState: NetworkState
@@ -44,7 +46,7 @@ class DoublePageReaderFragment : BaseReaderFragment<FragmentReaderDoubleBinding>
 		super.onViewBindingCreated(binding, savedInstanceState)
 		with(binding.recyclerView) {
 			adapter = readerAdapter
-			addOnScrollListener(PageScrollListener())
+			addOnScrollListener(PageScrollListener(viewModel))
 			DoublePageSnapHelper().attachToRecyclerView(this)
 		}
 	}
@@ -54,28 +56,28 @@ class DoublePageReaderFragment : BaseReaderFragment<FragmentReaderDoubleBinding>
 		super.onDestroyView()
 	}
 
-	override suspend fun onPagesChanged(pages: List<ReaderPage>, pendingState: ReaderState?) =
+	override suspend fun onPagesChanged(pages: List<ReaderPage>, pendingState: ReaderState?) = coroutineScope {
-		coroutineScope {
+		val items = launch {
-			val items = async {
+			requireAdapter().setItems(pages)
-				requireAdapter().setItems(pages)
+			yield()
-				yield()
-			}
-			if (pendingState != null) {
-				val position = pages.indexOfFirst {
-					it.chapterId == pendingState.chapterId && it.index == pendingState.page
-				}
-				items.await()
-				if (position != -1) {
-					requireViewBinding().recyclerView.firstVisibleItemPosition = position or 1
-					notifyPageChanged(position)
-				} else {
-					Snackbar.make(requireView(), R.string.not_found_404, Snackbar.LENGTH_SHORT)
-						.show()
-				}
-			} else {
-				items.await()
-			}
 		}
+		if (pendingState != null) {
+			var position = pages.indexOfFirst {
+				it.chapterId == pendingState.chapterId && it.index == pendingState.page
+			}
+			items.join()
+			if (position != -1) {
+				position = position or 1
+				requireViewBinding().recyclerView.firstVisibleItemPosition = position
+				viewModel.onCurrentPageChanged(position, position + 1)
+			} else {
+				Snackbar.make(requireView(), R.string.not_found_404, Snackbar.LENGTH_SHORT)
+					.show()
+			}
+		} else {
+			items.join()
+		}
+	}
 
 	override fun onCreateAdapter() = DoublePagesAdapter(
 		lifecycleOwner = viewLifecycleOwner,
@@ -85,6 +87,16 @@ class DoublePageReaderFragment : BaseReaderFragment<FragmentReaderDoubleBinding>
 		exceptionResolver = exceptionResolver,
 	)
 
+	override fun onZoomIn() {
+		(viewBinding ?: return).recyclerView.pageHolders()
+			.forEach { it.onZoomIn() }
+	}
+
+	override fun onZoomOut() {
+		(viewBinding ?: return).recyclerView.pageHolders()
+			.forEach { it.onZoomOut() }
+	}
+
 	override fun switchPageBy(delta: Int) {
 		switchPageTo((requireViewBinding().recyclerView.currentItem() + delta) or 1, delta.absoluteValue > 1)
 	}
@@ -103,25 +115,38 @@ class DoublePageReaderFragment : BaseReaderFragment<FragmentReaderDoubleBinding>
 		)
 	}
 
-	private fun notifyPageChanged(page: Int) {
-		viewModel.onCurrentPageChanged(page)
-	}
-
 	private fun RecyclerView.currentItem(): Int {
 		val lm = layoutManager as LinearLayoutManager
 		return ((lm.findFirstVisibleItemPosition() + lm.findLastVisibleItemPosition()) / 2f).toIntUp()
 	}
 
-	private inner class PageScrollListener : RecyclerView.OnScrollListener() {
+	private fun RecyclerView.pageHolders(): Sequence<PageHolder> {
+		val lm = layoutManager as? LinearLayoutManager ?: return emptySequence()
+		return (lm.findFirstVisibleItemPosition()..lm.findLastVisibleItemPosition()).asSequence()
+			.mapNotNull { findViewHolderForAdapterPosition(it) as? PageHolder }
+	}
 
-		private var lastPage = RecyclerView.NO_POSITION
+	private class PageScrollListener(
+		private val viewModel: ReaderViewModel,
+	) : RecyclerView.OnScrollListener() {
+
+		private var firstPos = RecyclerView.NO_POSITION
+		private var lastPos = RecyclerView.NO_POSITION
 
 		override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
 			super.onScrolled(recyclerView, dx, dy)
-			val page = recyclerView.currentItem()
+			val lm = recyclerView.layoutManager as? LinearLayoutManager
-			if (page != lastPage) {
+			if (lm == null) {
-				lastPage = page
+				firstPos = RecyclerView.NO_POSITION
-				notifyPageChanged(page)
+				lastPos = RecyclerView.NO_POSITION
+				return
+			}
+			val newFirstPos = lm.findFirstVisibleItemPosition()
+			val newLastPos = lm.findLastVisibleItemPosition()
+			if (newFirstPos != firstPos || newLastPos != lastPos) {
+				firstPos = newFirstPos
+				lastPos = newLastPos
+				viewModel.onCurrentPageChanged(newFirstPos, newLastPos)
 			}
 		}
 	}

app/src/main/res/drawable/ic_pager_double_ltr.xml

@@ -0,0 +1,24 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+  <path
+      android:fillColor="#FF000000"
+      android:pathData="M4,4C2.89,4 2,4.89 2,6L2,18C2,19.11 2.89,20 4,20L9,20L9,18L8,18L6,18L4,18L4,6L6,6L8,6L9,6L9,4L4,4zM15,4L15,6L16,6L18,6L20,6L20,18L18,18L16,18L15,18L15,20L20,20C21.1,20 22,19.11 22,18L22,6C22,4.89 21.1,4 20,4L15,4z"/>
+  <path
+      android:fillColor="#FF000000"
+      android:pathData="m11,22.43v-3h2v3z"/>
+  <path
+      android:fillColor="#FF000000"
+      android:pathData="m13,1.57v3h-2v-3h2"/>
+  <path
+      android:fillColor="#FF000000"
+      android:pathData="m11,17.43v-3h2v3h-2"/>
+  <path
+      android:fillColor="#FF000000"
+      android:pathData="m11,9.57v-3h2v3h-2"/>
+  <path
+      android:fillColor="#FF000000"
+      android:pathData="m14.5,15v-2h-7v-2h7V9l4,3 -4,3"/>
+</vector>

app/src/main/res/layout/sheet_reader_config.xml

@@ -119,6 +119,15 @@
 					android:text="@string/webtoon"
 					app:icon="@drawable/ic_script" />
 
+				<com.google.android.material.button.MaterialButton
+					android:id="@+id/button_double"
+					style="@style/Widget.Kotatsu.ToggleButton.Vertical"
+					android:layout_width="0dp"
+					android:layout_height="wrap_content"
+					android:layout_weight="1"
+					android:text="@string/two_pages"
+					app:icon="@drawable/ic_pager_double_ltr" />
+
 			</com.google.android.material.button.MaterialButtonToggleGroup>
 
 			<TextView

app/src/main/res/values/strings.xml

@@ -567,4 +567,5 @@
 	<string name="incognito_mode_hint">Your reading progress will not be saved</string>
 	<string name="vertical">Vertical</string>
 	<string name="last_read">Last read</string>
+	<string name="two_pages">Two pages</string>
 </resources>