Add foldable device support (auto two-page)

app/build.gradle

@@ -155,6 +155,9 @@ dependencies {
 	implementation libs.androidx.work.runtime
 	implementation libs.guava
 
+    // Foldable/Window layout
+    implementation libs.androidx.window
+
 	implementation libs.androidx.room.runtime
 	implementation libs.androidx.room.ktx
 	ksp libs.androidx.room.compiler

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

@@ -138,6 +138,10 @@ class AppSettings @Inject constructor(@ApplicationContext context: Context) {
 		get() = prefs.getBoolean(KEY_READER_DOUBLE_PAGES, false)
 		set(value) = prefs.edit { putBoolean(KEY_READER_DOUBLE_PAGES, value) }
 
+	var isReaderDoubleOnFoldable: Boolean
+		get() = prefs.getBoolean(KEY_READER_DOUBLE_FOLDABLE, false)
+		set(value) = prefs.edit { putBoolean(KEY_READER_DOUBLE_FOLDABLE, value) }
+
 	@get:FloatRange(0.0, 1.0)
 	var readerDoublePagesSensitivity: Float
 		get() = prefs.getFloat(KEY_READER_DOUBLE_PAGES_SENSITIVITY, 0.5f)
@@ -682,6 +686,7 @@ class AppSettings @Inject constructor(@ApplicationContext context: Context) {
 		const val KEY_LOCAL_STORAGE = "local_storage"
 		const val KEY_READER_DOUBLE_PAGES = "reader_double_pages"
 		const val KEY_READER_DOUBLE_PAGES_SENSITIVITY = "reader_double_pages_sensitivity"
+		const val KEY_READER_DOUBLE_FOLDABLE = "reader_double_foldable"
 		const val KEY_READER_ZOOM_BUTTONS = "reader_zoom_buttons"
 		const val KEY_READER_CONTROL_LTR = "reader_taps_ltr"
 		const val KEY_READER_NAVIGATION_INVERTED = "reader_navigation_inverted"

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

@@ -24,10 +24,15 @@ import androidx.transition.Fade
 import androidx.transition.Slide
 import androidx.transition.TransitionManager
 import androidx.transition.TransitionSet
+import androidx.window.layout.FoldingFeature
+import androidx.window.layout.WindowInfoTracker
+import android.content.res.Configuration
 import com.google.android.material.snackbar.Snackbar
 import dagger.hilt.android.AndroidEntryPoint
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.onEach
+import kotlinx.coroutines.flow.launchIn
 import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.flow.distinctUntilChanged
 import kotlinx.coroutines.flow.flowOn
@@ -109,6 +114,8 @@ class ReaderActivity :
 	private var gestureInsets: Insets = Insets.NONE
     private lateinit var readerManager: ReaderManager
     private val hideUiRunnable = Runnable { setUiIsVisible(false) }
+    // Tracks whether the foldable device is in an unfolded state (half-opened or flat)
+    private var isFoldUnfolded: Boolean = false
 
 	override fun onCreate(savedInstanceState: Bundle?) {
 		super.onCreate(savedInstanceState)
@@ -187,6 +194,25 @@ class ReaderActivity :
 			viewBinding.zoomControl.isVisible = it
 		}
         addMenuProvider(ReaderMenuProvider(viewModel))
+
+        // Observe foldable window layout to auto-enable double-page if configured
+        WindowInfoTracker.getOrCreate(this)
+            .windowLayoutInfo(this)
+            .onEach { info ->
+                val fold = info.displayFeatures.filterIsInstance<FoldingFeature>().firstOrNull()
+                val unfolded = when (fold?.state) {
+                    FoldingFeature.State.HALF_OPENED, FoldingFeature.State.FLAT -> true
+                    else -> false
+                }
+                if (unfolded != isFoldUnfolded) {
+                    isFoldUnfolded = unfolded
+                    applyDoubleModeAuto()
+                }
+            }
+            .launchIn(lifecycleScope)
+
+        // Apply initial double-mode considering foldable setting
+        applyDoubleModeAuto()
     }
 
 	override fun getParentActivityIntent(): Intent? {
@@ -341,7 +367,17 @@ class ReaderActivity :
 	}
 
     override fun onDoubleModeChanged(isEnabled: Boolean) {
-		readerManager.setDoubleReaderMode(isEnabled)
+        // Combine manual toggle with foldable auto setting
+        applyDoubleModeAuto(isEnabled)
+    }
+
+    private fun applyDoubleModeAuto(manualEnabled: Boolean? = null) {
+        val isLandscape = resources.configuration.orientation == Configuration.ORIENTATION_LANDSCAPE
+        // Auto double-page on foldable when device is unfolded (half-opened or flat)
+        val autoFoldable = settings.isReaderDoubleOnFoldable && isFoldUnfolded
+        val manualLandscape = (manualEnabled ?: settings.isReaderDoubleOnLandscape) && isLandscape
+        val autoEnabled = autoFoldable || manualLandscape
+        readerManager.setDoubleReaderMode(autoEnabled)
     }
 
 	private fun setKeepScreenOn(isKeep: Boolean) {

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

@@ -49,7 +49,7 @@ class ReaderManager(
 	fun setDoubleReaderMode(isEnabled: Boolean) {
 		val mode = currentMode
 		val prevReader = currentReader?.javaClass
-		invalidateTypesMap(isEnabled && isLandscape())
+		invalidateTypesMap(isEnabled)
 		val newReader = modeMap[mode]
 		if (mode != null && newReader != prevReader) {
 			replace(mode)

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

@@ -91,6 +91,8 @@ class ReaderConfigSheet :
 			binding.buttonVertical.isChecked = mode == ReaderMode.VERTICAL
 			binding.switchDoubleReader.isChecked = settings.isReaderDoubleOnLandscape
 			binding.switchDoubleReader.isEnabled = mode == ReaderMode.STANDARD || mode == ReaderMode.REVERSED
+			binding.switchDoubleFoldable.isChecked = settings.isReaderDoubleOnFoldable
+			binding.switchDoubleFoldable.isEnabled = binding.switchDoubleReader.isEnabled
 			binding.sliderDoubleSensitivity.setValueRounded(settings.readerDoublePagesSensitivity * 100f)
 			binding.sliderDoubleSensitivity.setLabelFormatter(IntPercentLabelFormatter(binding.root.context))
 			binding.adjustSensitivitySlider(withAnimation = false)
@@ -104,6 +106,7 @@ class ReaderConfigSheet :
 		binding.buttonScrollTimer.setOnClickListener(this)
 			binding.buttonBookmark.setOnClickListener(this)
 			binding.switchDoubleReader.setOnCheckedChangeListener(this)
+			binding.switchDoubleFoldable.setOnCheckedChangeListener(this)
 			binding.sliderDoubleSensitivity.addOnChangeListener(this)
 
 		viewModel.isBookmarkAdded.observe(viewLifecycleOwner) {
@@ -182,6 +185,12 @@ class ReaderConfigSheet :
 					viewBinding?.adjustSensitivitySlider(withAnimation = true)
 					findParentCallback(Callback::class.java)?.onDoubleModeChanged(isChecked)
 				}
+
+				R.id.switch_double_foldable -> {
+					settings.isReaderDoubleOnFoldable = isChecked
+					// Re-evaluate double-page considering foldable state and current manual toggle
+					findParentCallback(Callback::class.java)?.onDoubleModeChanged(settings.isReaderDoubleOnLandscape)
+				}
 			}
 		}
 
@@ -206,6 +215,7 @@ class ReaderConfigSheet :
 		}
 		viewBinding?.run {
 			switchDoubleReader.isEnabled = newMode == ReaderMode.STANDARD || newMode == ReaderMode.REVERSED
+			switchDoubleFoldable.isEnabled = switchDoubleReader.isEnabled
 			adjustSensitivitySlider(withAnimation = true)
 		}
 		if (newMode == mode) {
@@ -242,12 +252,18 @@ class ReaderConfigSheet :
 	}
 
     private fun SheetReaderConfigBinding.adjustSensitivitySlider(withAnimation: Boolean) {
-        val isSliderVisible = switchDoubleReader.isEnabled && switchDoubleReader.isChecked
+        val isSubOptionsVisible = switchDoubleReader.isEnabled && switchDoubleReader.isChecked
-        if (isSliderVisible != sliderDoubleSensitivity.isVisible && withAnimation) {
+        val needTransition = withAnimation && (
+            (isSubOptionsVisible != sliderDoubleSensitivity.isVisible) ||
+            (isSubOptionsVisible != textDoubleSensitivity.isVisible) ||
+            (isSubOptionsVisible != switchDoubleFoldable.isVisible)
+        )
+        if (needTransition) {
             TransitionManager.beginDelayedTransition(layoutMain)
         }
-        sliderDoubleSensitivity.isVisible = isSliderVisible
+        sliderDoubleSensitivity.isVisible = isSubOptionsVisible
-        textDoubleSensitivity.isVisible = isSliderVisible
+        textDoubleSensitivity.isVisible = isSubOptionsVisible
+        switchDoubleFoldable.isVisible = isSubOptionsVisible
     }
 
 	interface Callback {

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

@@ -130,6 +130,21 @@
                 android:textColor="?colorOnSurfaceVariant"
                 app:drawableStartCompat="@drawable/ic_split_horizontal" />
 
+            <com.google.android.material.materialswitch.MaterialSwitch
+                android:id="@+id/switch_double_foldable"
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:layout_marginTop="@dimen/margin_small"
+                android:drawablePadding="?android:listPreferredItemPaddingStart"
+                android:minHeight="?android:listPreferredItemHeightSmall"
+                android:paddingStart="?android:listPreferredItemPaddingStart"
+                android:paddingEnd="?android:listPreferredItemPaddingEnd"
+                android:text="@string/auto_double_foldable"
+                android:textAppearance="@style/TextAppearance.Kotatsu.GridTitle"
+                android:textColor="?colorOnSurfaceVariant"
+                android:visibility="gone"
+                tools:visibility="visible" />
+
             <TextView
                 android:id="@+id/text_double_sensitivity"
                 android:layout_width="match_parent"

app/src/main/res/values-zh-rCN/strings.xml

@@ -866,4 +866,5 @@
     <string name="pull_bottom_no_next">到底了</string>
     <string name="enable_pull_gesture_title">启用推拉手势</string>
     <string name="enable_pull_gesture_summary">条漫模式下使用推拉手势切换章节</string>
+    <string name="auto_double_foldable">折叠设备自动双页</string>
 </resources>

app/src/main/res/values-zh-rTW/strings.xml

@@ -661,4 +661,5 @@
     <string name="download_new_chapters">下載新的漫畫章節</string>
     <string name="enable_all_sources">啟用所有漫畫來源</string>
     <string name="all_sources_enabled">所有漫畫來源已啟用</string>
+    <string name="auto_double_foldable">摺疊設備自動雙頁</string>
 </resources>

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

@@ -579,6 +579,8 @@
     <string name="none">None</string>
     <string name="config_reset_confirm">Reset settings to default values? This action cannot be undone.</string>
     <string name="use_two_pages_landscape">Use two pages layout on landscape orientation (beta)</string>
+    <string name="auto_double_foldable">Auto Two-Page On Foldable</string>
+    <string name="auto_double_foldable_summary">Enable two-page layout when device has a separating hinge</string>
     <string name="two_page_scroll_sensitivity">Two-Page Scroll Sensitivity</string>
     <string name="default_webtoon_zoom_out">Default webtoon zoom out</string>
     <string name="fullscreen_mode">Fullscreen mode</string>

gradle/libs.versions.toml

@@ -49,6 +49,7 @@ viewpager2 = "1.1.0"
 webkit = "1.14.0"
 workRuntime = "2.10.5"
 workinspector = "1.2"
+window = "1.3.0"
 
 [libraries]
 acra-dialog = { module = "ch.acra:acra-dialog", version.ref = "acra" }
@@ -115,6 +116,7 @@ okhttp-tls = { module = "com.squareup.okhttp3:okhttp-tls", version.ref = "okhttp
 okio = { module = "com.squareup.okio:okio", version.ref = "okio" }
 ssiv = { module = "com.github.KotatsuApp:subsampling-scale-image-view", version.ref = "ssiv" }
 workinspector = { module = "com.github.Koitharu:WorkInspector", version.ref = "workinspector" }
+androidx-window = { module = "androidx.window:window", version.ref = "window" }
 
 [plugins]
 android-application = { id = "com.android.application", version.ref = "gradle" }