Implement invert double pages

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

@@ -1256,7 +1256,8 @@ class ReaderActivity : BaseRxActivity<ReaderActivityBinding, ReaderPresenter>()
         val pages = page.chapter.pages ?: return
 
         val currentPage = if (hasExtraPage) {
-            if (resources.isLTR) "${page.number}-${page.number + 1}" else "${page.number + 1}-${page.number}"
+            val invertDoublePage = (viewer as? PagerViewer)?.config?.invertDoublePages ?: false
+            if (resources.isLTR xor invertDoublePage) "${page.number}-${page.number + 1}" else "${page.number + 1}-${page.number}"
         } else {
             "${page.number}"
         }

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

@@ -88,6 +88,7 @@ class ReaderReadingModeSettings @JvmOverloads constructor(context: Context, attr
         // SY -->
         binding.pagerPrefsGroup.pageTransitionsPager.bindToPreference(preferences.pageTransitionsPager())
         binding.pagerPrefsGroup.pageLayout.bindToPreference(preferences.pageLayout())
+        binding.pagerPrefsGroup.invertDoublePages.bindToPreference(preferences.invertDoublePages())
         // SY <--
     }
 

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

@@ -137,6 +137,8 @@ class PagerConfig(
                 }
             )
 
+        preferences.invertDoublePages()
+            .register({ invertDoublePages = it && dualPageSplit == false }, { imagePropertyChangedListener?.invoke() })
         // SY <--
     }
 

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

@@ -23,9 +23,6 @@ import eu.kanade.tachiyomi.util.system.ImageUtil
 import eu.kanade.tachiyomi.util.system.dpToPx
 import eu.kanade.tachiyomi.util.system.logcat
 import eu.kanade.tachiyomi.widget.ViewPagerAdapter
-import kotlinx.coroutines.CoroutineScope
-import kotlinx.coroutines.Dispatchers
-import kotlinx.coroutines.Job
 import kotlinx.coroutines.delay
 import logcat.LogPriority
 import rx.Observable
@@ -104,12 +101,10 @@ class PagerPageHolder(
     var extraStatus: Int = 0
     var progress: Int = 0
     var extraProgress: Int = 0
-    var scope: CoroutineScope? = null
     // SY <--
 
     init {
         addView(progressIndicator)
-        scope = CoroutineScope(Job() + Dispatchers.Default)
         observeStatus()
     }
 
@@ -393,7 +388,7 @@ class PagerPageHolder(
             logcat(LogPriority.ERROR, e) { "Cannot combine pages" }
             return imageBytes.inputStream()
         }
-        scope?.launchUI { progressIndicator.setProgress(96) }
+        viewer.scope.launchUI { progressIndicator.setProgress(96) }
         val height = imageBitmap.height
         val width = imageBitmap.width
 
@@ -417,7 +412,7 @@ class PagerPageHolder(
             logcat(LogPriority.ERROR, e) { "Cannot combine pages" }
             return imageBytes.inputStream()
         }
-        scope?.launchUI { progressIndicator.setProgress(97) }
+        viewer.scope.launchUI { progressIndicator.setProgress(97) }
         val height2 = imageBitmap2.height
         val width2 = imageBitmap2.width
 
@@ -429,12 +424,12 @@ class PagerPageHolder(
             splitDoublePages()
             return imageBytes.inputStream()
         }
-        val isLTR = (viewer !is R2LPagerViewer).xor(viewer.config.invertDoublePages)
+        val isLTR = (viewer !is R2LPagerViewer) xor viewer.config.invertDoublePages
 
         imageStream.close()
         imageStream2.close()
         return ImageUtil.mergeBitmaps(imageBitmap, imageBitmap2, isLTR, viewer.config.pageCanvasColor) {
-            scope?.launchUI {
+            viewer.scope.launchUI {
                 if (it == 100) {
                     progressIndicator.hide()
                 } else {
@@ -445,7 +440,7 @@ class PagerPageHolder(
     }
 
     private fun splitDoublePages() {
-        scope?.launchUI {
+        viewer.scope.launchUI {
             delay(100)
             viewer.splitDoublePages(page)
             if (extraPage?.fullPage == true || page.fullPage) {

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

@@ -88,6 +88,15 @@
         android:textColor="?android:attr/textColorSecondary"
         android:text="@string/pref_page_transitions" />
 
+    <com.google.android.material.switchmaterial.SwitchMaterial
+        android:id="@+id/invert_double_pages"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:paddingStart="16dp"
+        android:paddingEnd="16dp"
+        android:textColor="?android:attr/textColorSecondary"
+        android:text="@string/invert_double_pages" />
+
     <androidx.constraintlayout.widget.Group
         android:id="@+id/tapping_prefs_group"
         android:layout_width="wrap_content"