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Add EdgeTapNavigation to trigger page turns on edge taps (#55)
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6 files changed

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‎CHANGELOG.md‎

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@@ -12,6 +12,18 @@ All notable changes to this project will be documented in this file. Take a look
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* The PDF navigator now honors the publication reading progression with support for right-to-left and horizontal scrolling.
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* The default (auto) reading progression for PDF is top-to-bottom, which is vertical scrolling.
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* A new convenience utility `EdgeTapNavigation` to trigger page turns while tapping the screen edges.
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* It takes into account the navigator reading progression to move into the right direction.
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* Call it from the `VisualNavigator.Listener.onTap()` callback as demonstrated below:
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```kotlin
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override fun onTap(point: PointF): Boolean {
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val navigated = edgeTapNavigation.onTap(point, requireView())
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if (!navigated) {
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// Fallback action, for example toggling the app bar.
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}
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return true
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}
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```
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### Fixed
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‎readium/navigator/src/main/java/org/readium/r2/navigator/util/EdgeTapNavigation.kt‎

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package org.readium.r2.navigator.util
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import android.graphics.PointF
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import android.view.View
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import org.readium.r2.navigator.VisualNavigator
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import org.readium.r2.shared.publication.ReadingProgression
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/**
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* Convenience utility to handle page turns when tapping the edge of the screen.
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*
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* Call [EdgeTapNavigation.onTap] from the [VisualNavigator.Listener.onTap] callback to turn pages
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* automatically.
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*
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* @param navigator Navigator used to turn pages.
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* @param minimumEdgeSize The minimum edge dimension triggering page turns, in pixels.
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* @param edgeThresholdPercent The percentage of the viewport dimension used to compute the edge
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* dimension. When null, minimumEdgeSize will be used instead.
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* @param animatedTransition Indicates whether the page turns should be animated.
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*/
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class EdgeTapNavigation(
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private val navigator: VisualNavigator,
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private val minimumEdgeSize: Double = 200.0,
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private val edgeThresholdPercent: Double? = 0.3,
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private val animatedTransition: Boolean = false,
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) {
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private enum class Transition {
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FORWARD, BACKWARD, NONE;
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fun reverse() = when (this) {
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FORWARD -> BACKWARD
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BACKWARD -> FORWARD
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NONE -> NONE
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}
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}
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/**
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* Handles a tap in the navigator viewport and returns whether it was successful.
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*
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* To be called from [VisualNavigator.Listener.onTap].
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*
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* @param view Navigator view from which the point is relative.
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*/
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fun onTap(point: PointF, view: View): Boolean {
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val horizontalEdgeSize by lazy {
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if (edgeThresholdPercent != null)
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(edgeThresholdPercent * view.width).coerceAtLeast(minimumEdgeSize)
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else minimumEdgeSize
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}
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val leftRange by lazy { 0.0..horizontalEdgeSize }
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val rightRange by lazy { (view.width - horizontalEdgeSize)..view.width.toDouble() }
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val verticalEdgeSize by lazy {
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if (edgeThresholdPercent != null)
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(edgeThresholdPercent * view.height).coerceAtLeast(minimumEdgeSize)
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else minimumEdgeSize
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}
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val topRange by lazy { 0.0..verticalEdgeSize }
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val bottomRange by lazy { (view.height - verticalEdgeSize)..view.height.toDouble() }
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val isHorizontal = navigator.readingProgression.isHorizontal ?: true
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val isReverse = when (navigator.readingProgression) {
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ReadingProgression.LTR, ReadingProgression.TTB, ReadingProgression.AUTO -> false
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ReadingProgression.RTL, ReadingProgression.BTT -> true
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}
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var transition: Transition =
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if (isHorizontal) {
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when {
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rightRange.contains(point.x) -> Transition.FORWARD
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leftRange.contains(point.x) -> Transition.BACKWARD
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else -> Transition.NONE
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}
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} else {
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when {
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bottomRange.contains(point.y) -> Transition.FORWARD
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topRange.contains(point.y) -> Transition.BACKWARD
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else -> Transition.NONE
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}
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}
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if (isReverse) {
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transition = transition.reverse()
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}
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return when (transition) {
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Transition.FORWARD -> navigator.goForward(animated = animatedTransition)
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Transition.BACKWARD -> navigator.goBackward(animated = animatedTransition)
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Transition.NONE -> false
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}
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}
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}

‎test-app/src/main/java/org/readium/r2/testapp/reader/EpubReaderFragment.kt‎

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}
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}
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override fun onTap(point: PointF): Boolean {
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requireActivity().toggleSystemUi()
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return true
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}
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private fun showSearchFragment() {
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childFragmentManager.commit {
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childFragmentManager.findFragmentByTag(SEARCH_FRAGMENT_TAG)?.let { remove(it) }

‎test-app/src/main/java/org/readium/r2/testapp/reader/ImageReaderFragment.kt‎

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package org.readium.r2.testapp.reader
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import android.graphics.PointF
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import android.os.Bundle
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import android.view.LayoutInflater
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import android.view.View
@@ -17,7 +16,6 @@ import org.readium.r2.navigator.Navigator
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import org.readium.r2.navigator.image.ImageNavigatorFragment
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import org.readium.r2.shared.publication.Publication
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import org.readium.r2.testapp.R
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import org.readium.r2.testapp.utils.toggleSystemUi
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class ImageReaderFragment : VisualReaderFragment(), ImageNavigatorFragment.Listener {
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return view
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}
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override fun onTap(point: PointF): Boolean {
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val viewWidth = requireView().width
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val leftRange = 0.0..(0.2 * viewWidth)
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when {
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leftRange.contains(point.x) -> navigator.goBackward(animated = true)
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leftRange.contains(viewWidth - point.x) -> navigator.goForward(animated = true)
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else -> requireActivity().toggleSystemUi()
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}
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return true
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}
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companion object {
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const val NAVIGATOR_FRAGMENT_TAG = "navigator"

‎test-app/src/main/java/org/readium/r2/testapp/reader/PdfReaderFragment.kt‎

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requireActivity().finish()
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}
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override fun onTap(point: PointF): Boolean {
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val viewWidth = requireView().width
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val leftRange = 0.0..(0.2 * viewWidth)
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when {
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leftRange.contains(point.x) -> navigator.goBackward()
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leftRange.contains(viewWidth - point.x) -> navigator.goForward()
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else -> requireActivity().toggleSystemUi()
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}
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return true
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}
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companion object {
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const val NAVIGATOR_FRAGMENT_TAG = "navigator"

‎test-app/src/main/java/org/readium/r2/testapp/reader/VisualReaderFragment.kt‎

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package org.readium.r2.testapp.reader
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import android.graphics.PointF
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import android.os.Bundle
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import android.view.LayoutInflater
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import android.view.View
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import androidx.fragment.app.Fragment
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import org.readium.r2.navigator.DecorableNavigator
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import org.readium.r2.navigator.ExperimentalDecorator
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import org.readium.r2.navigator.VisualNavigator
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import org.readium.r2.navigator.util.EdgeTapNavigation
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import org.readium.r2.testapp.R
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import org.readium.r2.testapp.databinding.FragmentReaderBinding
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import org.readium.r2.testapp.utils.clearPadding
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import org.readium.r2.testapp.utils.hideSystemUi
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import org.readium.r2.testapp.utils.padSystemUi
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import org.readium.r2.testapp.utils.showSystemUi
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import org.readium.r2.testapp.utils.*
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/*
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* Adds fullscreen support to the BaseReaderFragment
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*/
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abstract class VisualReaderFragment : BaseReaderFragment() {
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abstract class VisualReaderFragment : BaseReaderFragment(), VisualNavigator.Listener {
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private lateinit var navigatorFragment: Fragment
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container.clearPadding()
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}
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}
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// VisualNavigator.Listener
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override fun onTap(point: PointF): Boolean {
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val navigated = edgeTapNavigation.onTap(point, requireView())
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if (!navigated) {
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requireActivity().toggleSystemUi()
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}
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return true
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}
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private val edgeTapNavigation by lazy {
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EdgeTapNavigation(
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navigator = navigator as VisualNavigator
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)
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}
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}

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