Option to invert double pages

Closes #725

app/src/main/java/eu/kanade/tachiyomi/data/preference/PreferenceKeys.kt

@@ -71,6 +71,8 @@ object PreferenceKeys {
 
     const val pageLayout = "page_layout"
 
+    const val invertDoublePages = "invert_double_pages"
+
     const val showNavigationOverlayNewUser = "reader_navigation_overlay_new_user"
     const val showNavigationOverlayNewUserWebtoon = "reader_navigation_overlay_new_user_webtoon"
 

app/src/main/java/eu/kanade/tachiyomi/data/preference/PreferencesHelper.kt

@@ -154,6 +154,8 @@ class PreferencesHelper(val context: Context) {
 
     fun pageLayout() = flowPrefs.getInt(Keys.pageLayout, PageLayout.AUTOMATIC)
 
+    fun invertDoublePages() = flowPrefs.getBoolean(Keys.invertDoublePages, false)
+
     fun showNavigationOverlayNewUser() = flowPrefs.getBoolean(Keys.showNavigationOverlayNewUser, true)
 
     fun showNavigationOverlayNewUserWebtoon() = flowPrefs.getBoolean(Keys.showNavigationOverlayNewUserWebtoon, true)

app/src/main/java/eu/kanade/tachiyomi/ui/reader/settings/ReaderPagedView.kt

@@ -3,10 +3,12 @@ package eu.kanade.tachiyomi.ui.reader.settings
 import android.app.Activity
 import android.content.Context
 import android.util.AttributeSet
+import androidx.core.view.isVisible
 import com.davemorrissey.labs.subscaleview.SubsamplingScaleImageView
 import eu.kanade.tachiyomi.R
 import eu.kanade.tachiyomi.databinding.ReaderPagedLayoutBinding
 import eu.kanade.tachiyomi.ui.reader.ReaderActivity
+import eu.kanade.tachiyomi.ui.reader.viewer.pager.PageLayout
 import eu.kanade.tachiyomi.util.bindToPreference
 import eu.kanade.tachiyomi.util.lang.addBetaTag
 import eu.kanade.tachiyomi.util.view.visibleIf
@@ -17,34 +19,44 @@ class ReaderPagedView @JvmOverloads constructor(context: Context, attrs: Attribu
 
     override fun inflateBinding() = ReaderPagedLayoutBinding.bind(this)
     override fun initGeneralPreferences() {
-        binding.scaleType.bindToPreference(preferences.imageScaleType(), 1) {
+        with(binding) {
+            scaleType.bindToPreference(preferences.imageScaleType(), 1) {
+                val mangaViewer = (context as? ReaderActivity)?.presenter?.getMangaViewer() ?: 0
+                val isWebtoonView =
+                    mangaViewer == ReaderActivity.WEBTOON || mangaViewer == ReaderActivity.VERTICAL_PLUS
+                updatePagedGroup(!isWebtoonView)
+            }
+            zoomStart.bindToPreference(preferences.zoomStart(), 1)
+            cropBorders.bindToPreference(preferences.cropBorders())
+            pageTransitions.bindToPreference(preferences.pageTransitions())
+            pagerNav.bindToPreference(preferences.navigationModePager())
+            pagerInvert.bindToPreference(preferences.pagerNavInverted())
+            extendPastCutout.bindToPreference(preferences.pagerCutoutBehavior())
+            pageLayout.bindToPreference(preferences.pageLayout()) {
+                val mangaViewer = (context as? ReaderActivity)?.presenter?.getMangaViewer() ?: 0
+                val isWebtoonView =
+                    mangaViewer == ReaderActivity.WEBTOON || mangaViewer == ReaderActivity.VERTICAL_PLUS
+                updatePagedGroup(!isWebtoonView)
+            }
+            invertDoublePages.bindToPreference(preferences.invertDoublePages())
+
+            pageLayout.title = pageLayout.title.toString().addBetaTag(context)
+
             val mangaViewer = (context as? ReaderActivity)?.presenter?.getMangaViewer() ?: 0
-            val isWebtoonView = mangaViewer == ReaderActivity.WEBTOON || mangaViewer == ReaderActivity.VERTICAL_PLUS
+            val isWebtoonView =
+                mangaViewer == ReaderActivity.WEBTOON || mangaViewer == ReaderActivity.VERTICAL_PLUS
+            val hasMargins = mangaViewer == ReaderActivity.VERTICAL_PLUS
+            cropBordersWebtoon.bindToPreference(if (hasMargins) preferences.cropBorders() else preferences.cropBordersWebtoon())
+            webtoonSidePadding.bindToIntPreference(
+                preferences.webtoonSidePadding(),
+                R.array.webtoon_side_padding_values
+            )
+            webtoonEnableZoomOut.bindToPreference(preferences.webtoonEnableZoomOut())
+            webtoonNav.bindToPreference(preferences.navigationModeWebtoon())
+            webtoonInvert.bindToPreference(preferences.webtoonNavInverted())
+
             updatePagedGroup(!isWebtoonView)
         }
-        binding.zoomStart.bindToPreference(preferences.zoomStart(), 1)
-        binding.cropBorders.bindToPreference(preferences.cropBorders())
-        binding.pageTransitions.bindToPreference(preferences.pageTransitions())
-        binding.pagerNav.bindToPreference(preferences.navigationModePager())
-        binding.pagerInvert.bindToPreference(preferences.pagerNavInverted())
-        binding.extendPastCutout.bindToPreference(preferences.pagerCutoutBehavior())
-        binding.pageLayout.bindToPreference(preferences.pageLayout())
-
-        binding.pageLayout.title = binding.pageLayout.title.toString().addBetaTag(context)
-
-        val mangaViewer = (context as? ReaderActivity)?.presenter?.getMangaViewer() ?: 0
-        val isWebtoonView = mangaViewer == ReaderActivity.WEBTOON || mangaViewer == ReaderActivity.VERTICAL_PLUS
-        val hasMargins = mangaViewer == ReaderActivity.VERTICAL_PLUS
-        binding.cropBordersWebtoon.bindToPreference(if (hasMargins) preferences.cropBorders() else preferences.cropBordersWebtoon())
-        binding.webtoonSidePadding.bindToIntPreference(
-            preferences.webtoonSidePadding(),
-            R.array.webtoon_side_padding_values
-        )
-        binding.webtoonEnableZoomOut.bindToPreference(preferences.webtoonEnableZoomOut())
-        binding.webtoonNav.bindToPreference(preferences.navigationModeWebtoon())
-        binding.webtoonInvert.bindToPreference(preferences.webtoonNavInverted())
-
-        updatePagedGroup(!isWebtoonView)
     }
 
     fun updatePrefs() {
@@ -84,6 +96,7 @@ class ReaderPagedView @JvmOverloads constructor(context: Context, attrs: Attribu
         } else {
             false
         }
-        binding.extendPastCutout.visibleIf(show && isFullFit && hasCutout)
+        binding.extendPastCutout.isVisible = show && isFullFit && hasCutout
+        binding.invertDoublePages.isVisible = show && preferences.pageLayout().get() != PageLayout.SINGLE_PAGE
     }
 }

app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/pager/PagerConfig.kt

@@ -48,6 +48,8 @@ class PagerConfig(private val viewer: PagerViewer, preferences: PreferencesHelpe
             }
         }
 
+    var invertDoublePages = false
+
     var autoDoublePages = preferences.pageLayout().get() == PageLayout.AUTOMATIC
 
     init {
@@ -87,6 +89,9 @@ class PagerConfig(private val viewer: PagerViewer, preferences: PreferencesHelpe
         preferences.readerTheme()
             .register({ readerTheme = it }, { imagePropertyChangedListener?.invoke() })
 
+        preferences.invertDoublePages()
+            .register({ invertDoublePages = it }, { imagePropertyChangedListener?.invoke() })
+
         preferences.pageLayout()
             .asFlow()
             .drop(1)

app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/pager/PagerPageHolder.kt

@@ -689,7 +689,7 @@ class PagerPageHolder(
         val result = Bitmap.createBitmap(width + width2, max(height, height2), Bitmap.Config.ARGB_8888)
         val canvas = Canvas(result)
         canvas.drawColor(if (viewer.config.readerTheme >= 2 || viewer.config.readerTheme == 0) Color.WHITE else Color.BLACK)
-        val isLTR = viewer !is R2LPagerViewer
+        val isLTR = (viewer !is R2LPagerViewer).xor(viewer.config.invertDoublePages)
         val upperPart = Rect(
             if (isLTR) 0 else width2,
             (maxHeight - imageBitmap.height) / 2,

app/src/main/java/eu/kanade/tachiyomi/ui/setting/SettingsReaderController.kt

@@ -244,6 +244,11 @@ class SettingsReaderController : SettingsController() {
             infoPreference(R.string.automatic_can_still_switch).apply {
                 preferences.pageLayout().asImmediateFlow { isVisible = it == PageLayout.AUTOMATIC }.launchIn(viewScope)
             }
+            switchPreference {
+                key = Keys.invertDoublePages
+                titleRes = R.string.invert_double_pages
+                defaultValue = false
+            }
         }
         preferenceCategory {
             titleRes = R.string.webtoon

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

@@ -64,6 +64,14 @@
             app:title="@string/zoom_start_position"
             android:entries="@array/zoom_start" />
 
+        <com.google.android.material.switchmaterial.SwitchMaterial
+            android:id="@+id/invert_double_pages"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:layout_marginTop="4dp"
+            android:text="@string/invert_double_pages"
+            android:textColor="?android:attr/textColorPrimary" />
+
         <com.google.android.material.switchmaterial.SwitchMaterial
             android:id="@+id/crop_borders"
             android:layout_width="match_parent"

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

@@ -322,6 +322,7 @@
     <string name="amount_of_pages_to_preload">The amount of pages to preload when reading. Higher values will result in a smoother reading experience, at the cost of higher cache and network usage.</string>
     <string name="reduces_banding_impacts_performance">Reduces banding, but impacts
         performance</string>
+    <string name="invert_double_pages">Invert double pages</string>
     <string name="crop_borders">Crop borders</string>
     <string name="use_custom_brightness">Use custom brightness</string>
     <string name="use_custom_color_filter">Use custom color filter</string>