Default webtoon zoom out option

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

@@ -361,6 +361,10 @@ class AppSettings @Inject constructor(@ApplicationContext context: Context) {
 	val isWebtoonZoomEnable: Boolean
 		get() = prefs.getBoolean(KEY_WEBTOON_ZOOM, true)
 
+	@get:FloatRange(from = 0.0, to = 0.5)
+	val defaultWebtoonZoomOut: Float
+		get() = prefs.getInt(KEY_WEBTOON_ZOOM_OUT, 0).coerceIn(0, 50) / 100f
+
 	@get:FloatRange(from = 0.0, to = 1.0)
 	var readerAutoscrollSpeed: Float
 		get() = prefs.getFloat(KEY_READER_AUTOSCROLL_SPEED, 0f)
@@ -538,6 +542,7 @@ class AppSettings @Inject constructor(@ApplicationContext context: Context) {
 		const val KEY_HISTORY_ORDER = "history_order"
 		const val KEY_FAVORITES_ORDER = "fav_order"
 		const val KEY_WEBTOON_ZOOM = "webtoon_zoom"
+		const val KEY_WEBTOON_ZOOM_OUT = "webtoon_zoom_out"
 		const val KEY_PREFETCH_CONTENT = "prefetch_content"
 		const val KEY_APP_LOCALE = "app_locale"
 		const val KEY_LOGGING_ENABLED = "logging"

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

@@ -21,6 +21,7 @@ import kotlinx.coroutines.flow.filterNotNull
 import kotlinx.coroutines.flow.first
 import kotlinx.coroutines.flow.flatMapLatest
 import kotlinx.coroutines.flow.flowOf
+import kotlinx.coroutines.flow.flowOn
 import kotlinx.coroutines.flow.launchIn
 import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.flow.onEach
@@ -128,6 +129,14 @@ class ReaderViewModel @Inject constructor(
 	val isWebtoonZooEnabled = observeIsWebtoonZoomEnabled()
 		.stateIn(viewModelScope + Dispatchers.Default, SharingStarted.Lazily, false)
 
+	val defaultWebtoonZoomOut = observeIsWebtoonZoomEnabled().flatMapLatest {
+		if (it) {
+			observeWebtoonZoomOut()
+		} else {
+			flowOf(0f)
+		}
+	}.flowOn(Dispatchers.Default)
+
 	val isZoomControlsEnabled = getObserveIsZoomControlEnabled().flatMapLatest { zoom ->
 		if (zoom) {
 			combine(readerMode, isWebtoonZooEnabled) { mode, ze -> ze || mode != ReaderMode.WEBTOON }
@@ -438,6 +447,11 @@ class ReaderViewModel @Inject constructor(
 		valueProducer = { isWebtoonZoomEnable },
 	)
 
+	private fun observeWebtoonZoomOut() = settings.observeAsFlow(
+		key = AppSettings.KEY_WEBTOON_ZOOM_OUT,
+		valueProducer = { defaultWebtoonZoomOut },
+	)
+
 	private fun getObserveIsZoomControlEnabled() = settings.observeAsFlow(
 		key = AppSettings.KEY_READER_ZOOM_BUTTONS,
 		valueProducer = { isReaderZoomButtonsEnabled },

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

@@ -7,6 +7,7 @@ import android.view.animation.DecelerateInterpolator
 import com.google.android.material.snackbar.Snackbar
 import dagger.hilt.android.AndroidEntryPoint
 import kotlinx.coroutines.coroutineScope
+import kotlinx.coroutines.flow.take
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.yield
 import org.koitharu.kotatsu.R
@@ -55,6 +56,9 @@ class WebtoonReaderFragment : BaseReaderFragment<FragmentReaderWebtoonBinding>()
 		viewModel.isWebtoonZooEnabled.observe(viewLifecycleOwner) {
 			binding.frame.isZoomEnable = it
 		}
+		viewModel.defaultWebtoonZoomOut.take(1).observe(viewLifecycleOwner) {
+			binding.frame.zoom = 1f - it
+		}
 	}
 
 	override fun onDestroyView() {

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

@@ -5,6 +5,7 @@ import android.util.AttributeSet
 import android.view.View
 import androidx.core.view.ViewCompat.TYPE_TOUCH
 import androidx.core.view.forEach
+import androidx.core.view.iterator
 import androidx.recyclerview.widget.LinearLayoutManager
 import androidx.recyclerview.widget.RecyclerView
 import java.util.Collections
@@ -18,6 +19,7 @@ class WebtoonRecyclerView @JvmOverloads constructor(
 	private var onPageScrollListeners = LinkedList<OnWebtoonScrollListener>()
 	private val scrollDispatcher = WebtoonScrollDispatcher()
 	private val detachedViews = Collections.newSetFromMap(WeakHashMap<View, Boolean>())
+	private var isFixingScroll = false
 
 	override fun onChildDetachedFromWindow(child: View) {
 		super.onChildDetachedFromWindow(child)
@@ -121,6 +123,36 @@ class WebtoonRecyclerView @JvmOverloads constructor(
 		}
 	}
 
+	 fun updateChildrenScroll() {
+		if (isFixingScroll) {
+			return
+		}
+		isFixingScroll = true
+		for (child in this) {
+			val ssiv = (child as WebtoonFrameLayout).target
+			if (adjustScroll(child, ssiv)) {
+				break
+			}
+		}
+		isFixingScroll = false
+	}
+
+	private fun adjustScroll(child: View, ssiv: WebtoonImageView): Boolean = when {
+		child.bottom < height && ssiv.getScroll() < ssiv.getScrollRange() -> {
+			val distance = minOf(height - child.bottom, ssiv.getScrollRange() - ssiv.getScroll())
+			ssiv.scrollBy(distance)
+			true
+		}
+
+		child.top > 0 && ssiv.getScroll() > 0 -> {
+			val distance = minOf(child.top, ssiv.getScroll())
+			ssiv.scrollBy(-distance)
+			true
+		}
+
+		else -> false
+	}
+
 	private class WebtoonScrollDispatcher {
 
 		private var firstPos = NO_POSITION

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

@@ -16,6 +16,7 @@ import android.view.animation.AccelerateDecelerateInterpolator
 import android.view.animation.DecelerateInterpolator
 import android.widget.FrameLayout
 import android.widget.OverScroller
+import androidx.core.animation.doOnEnd
 import androidx.core.view.GestureDetectorCompat
 import androidx.core.view.ViewConfigurationCompat
 import org.koitharu.kotatsu.core.ui.widgets.ZoomControl
@@ -32,8 +33,6 @@ class WebtoonScalingFrame @JvmOverloads constructor(
 	ScaleGestureDetector.OnScaleGestureListener,
 	ZoomControl.ZoomControlListener {
 
-	private val targetChild by lazy(LazyThreadSafetyMode.NONE) { getChildAt(0) as WebtoonRecyclerView }
-
 	private val scaleDetector = ScaleGestureDetector(context, this)
 	private val gestureDetector = GestureDetectorCompat(context, GestureListener())
 	private val overScroller = OverScroller(context, AccelerateDecelerateInterpolator())
@@ -59,6 +58,15 @@ class WebtoonScalingFrame @JvmOverloads constructor(
 			}
 		}
 
+	var zoom: Float
+		get() = scale
+		set(value) {
+			if (value != scale) {
+				scaleChild(value, halfWidth, halfHeight)
+				onPostScale(invalidateLayout = true)
+			}
+		}
+
 	init {
 		syncMatrixValues()
 	}
@@ -163,6 +171,7 @@ class WebtoonScalingFrame @JvmOverloads constructor(
 	}
 
 	private fun invalidateTarget() {
+		val targetChild = findTargetChild()
 		adjustBounds()
 		targetChild.run {
 			scaleX = scale
@@ -239,7 +248,19 @@ class WebtoonScalingFrame @JvmOverloads constructor(
 		return true
 	}
 
-	override fun onScaleEnd(p0: ScaleGestureDetector) = Unit
+	override fun onScaleEnd(p0: ScaleGestureDetector) {
+		onPostScale(invalidateLayout = false)
+	}
+
+	private fun onPostScale(invalidateLayout: Boolean) {
+		val target = findTargetChild()
+		target.post {
+			target.updateChildrenScroll()
+			if (invalidateLayout) {
+				target.requestLayout()
+			}
+		}
+	}
 
 	private fun smoothScaleTo(target: Float) {
 		val newScale = target.coerceIn(MIN_SCALE, MAX_SCALE)
@@ -248,10 +269,13 @@ class WebtoonScalingFrame @JvmOverloads constructor(
 			setDuration(context.getAnimationDuration(android.R.integer.config_shortAnimTime))
 			interpolator = DecelerateInterpolator()
 			addUpdateListener { scaleChild(it.animatedValue as Float, halfWidth, halfHeight) }
+			doOnEnd { onPostScale(invalidateLayout = false) }
 			start()
 		}
 	}
 
+	private fun findTargetChild() = getChildAt(0) as WebtoonRecyclerView
+
 	private inner class GestureListener : GestureDetector.SimpleOnGestureListener(), Runnable {
 
 		override fun onScroll(

app/src/main/kotlin/org/koitharu/kotatsu/settings/AppearanceSettingsFragment.kt

@@ -25,6 +25,7 @@ import org.koitharu.kotatsu.core.util.ext.toList
 import org.koitharu.kotatsu.parsers.util.names
 import org.koitharu.kotatsu.parsers.util.toTitleCase
 import org.koitharu.kotatsu.settings.utils.ActivityListPreference
+import org.koitharu.kotatsu.settings.utils.PercentSummaryProvider
 import org.koitharu.kotatsu.settings.utils.SliderPreference
 import javax.inject.Inject
 
@@ -38,14 +39,7 @@ class AppearanceSettingsFragment :
 
 	override fun onCreatePreferences(savedInstanceState: Bundle?, rootKey: String?) {
 		addPreferencesFromResource(R.xml.pref_appearance)
-		findPreference<SliderPreference>(AppSettings.KEY_GRID_SIZE)?.run {
-			val pattern = context.getString(R.string.percent_string_pattern)
-			summary = pattern.format(value.toString())
-			setOnPreferenceChangeListener { preference, newValue ->
-				preference.summary = pattern.format(newValue.toString())
-				true
-			}
-		}
+		findPreference<SliderPreference>(AppSettings.KEY_GRID_SIZE)?.summaryProvider = PercentSummaryProvider()
 		findPreference<ListPreference>(AppSettings.KEY_LIST_MODE)?.run {
 			entryValues = ListMode.entries.names()
 			setDefaultValueCompat(ListMode.GRID.name)

app/src/main/kotlin/org/koitharu/kotatsu/settings/ReaderSettingsFragment.kt

@@ -17,6 +17,8 @@ import org.koitharu.kotatsu.core.ui.BasePreferenceFragment
 import org.koitharu.kotatsu.core.util.ext.setDefaultValueCompat
 import org.koitharu.kotatsu.parsers.util.names
 import org.koitharu.kotatsu.settings.reader.ReaderTapGridConfigActivity
+import org.koitharu.kotatsu.settings.utils.PercentSummaryProvider
+import org.koitharu.kotatsu.settings.utils.SliderPreference
 
 @AndroidEntryPoint
 class ReaderSettingsFragment :
@@ -46,6 +48,7 @@ class ReaderSettingsFragment :
 			entryValues = ZoomMode.entries.names()
 			setDefaultValueCompat(ZoomMode.FIT_CENTER.name)
 		}
+		findPreference<SliderPreference>(AppSettings.KEY_WEBTOON_ZOOM_OUT)?.summaryProvider = PercentSummaryProvider()
 		updateReaderModeDependency()
 	}
 

app/src/main/kotlin/org/koitharu/kotatsu/settings/utils/PercentSummaryProvider.kt

@@ -0,0 +1,16 @@
+package org.koitharu.kotatsu.settings.utils
+
+import androidx.preference.Preference
+import org.koitharu.kotatsu.R
+
+class PercentSummaryProvider : Preference.SummaryProvider<SliderPreference> {
+
+	private var percentPattern: String? = null
+
+	override fun provideSummary(preference: SliderPreference): CharSequence? {
+		val pattern = percentPattern ?: preference.context.getString(R.string.percent_string_pattern).also {
+			percentPattern = it
+		}
+		return pattern.format(preference.value.toString())
+	}
+}

app/src/main/kotlin/org/koitharu/kotatsu/settings/utils/SliderPreference.kt

@@ -24,6 +24,7 @@ class SliderPreference @JvmOverloads constructor(
 	private var valueTo: Int = 100
 	private var stepSize: Int = 1
 	private var currentValue: Int = 0
+	private var isTickVisible: Boolean = false
 
 	var value: Int
 		get() = currentValue
@@ -46,10 +47,9 @@ class SliderPreference @JvmOverloads constructor(
 				R.styleable.SliderPreference_android_valueFrom,
 				valueFrom.toFloat(),
 			).toInt()
-			valueTo =
-				getFloat(R.styleable.SliderPreference_android_valueTo, valueTo.toFloat()).toInt()
-			stepSize =
-				getFloat(R.styleable.SliderPreference_android_stepSize, stepSize.toFloat()).toInt()
+			valueTo = getFloat(R.styleable.SliderPreference_android_valueTo, valueTo.toFloat()).toInt()
+			stepSize = getFloat(R.styleable.SliderPreference_android_stepSize, stepSize.toFloat()).toInt()
+			isTickVisible = getBoolean(R.styleable.SliderPreference_tickVisible, isTickVisible)
 		}
 	}
 
@@ -61,6 +61,7 @@ class SliderPreference @JvmOverloads constructor(
 		slider.valueFrom = valueFrom.toFloat()
 		slider.valueTo = valueTo.toFloat()
 		slider.stepSize = stepSize.toFloat()
+		slider.isTickVisible = isTickVisible
 		slider.setValueRounded(currentValue.toFloat())
 		slider.isEnabled = isEnabled
 	}
@@ -112,7 +113,7 @@ class SliderPreference @JvmOverloads constructor(
 	private fun syncValueInternal(sliderValue: Int) {
 		if (sliderValue != currentValue) {
 			if (callChangeListener(sliderValue)) {
-				setValueInternal(sliderValue, notifyChanged = false)
+				setValueInternal(sliderValue, notifyChanged = true)
 			}
 		}
 	}

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

@@ -23,6 +23,7 @@
 		<attr name="android:valueFrom" />
 		<attr name="android:valueTo" />
 		<attr name="android:stepSize" />
+		<attr name="tickVisible" />
 	</declare-styleable>
 
 	<declare-styleable name="ListItemTextView">

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

@@ -585,4 +585,5 @@
     <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="default_webtoon_zoom_out">Default webtoon zoom out</string>
 </resources>

app/src/main/res/xml/pref_reader.xml

@@ -28,6 +28,16 @@
 		android:summary="@string/webtoon_zoom_summary"
 		android:title="@string/webtoon_zoom" />
 
+	<org.koitharu.kotatsu.settings.utils.SliderPreference
+		android:dependency="webtoon_zoom"
+		android:key="webtoon_zoom_out"
+		android:stepSize="10"
+		android:title="@string/default_webtoon_zoom_out"
+		android:valueFrom="0"
+		android:valueTo="50"
+		app:defaultValue="0"
+		app:tickVisible="true" />
+
 	<SwitchPreferenceCompat
 		android:defaultValue="false"
 		android:key="reader_zoom_buttons"