Added dual page split setting (#4252)

* Add DualPageSplit option

* remove extra line

* Split double-page into two pages

* Remove !isAnimated check and add (ALPHA) to the label

* Fix missing insert pages

* Pager cleanup

* Add dual split to Webtoon and fix Vertical

* Fix L2R/R2L

* Add comments and refactor code in ImageUtil

* Use a simpler split solution in webtoon mode

Co-authored-by: weng <>
Co-authored-by: Andreas E <andreas.everos@gmail.com>

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

@@ -151,6 +151,14 @@
         android:textColor="?android:attr/textColorSecondary"
         app:layout_constraintTop_toBottomOf="@id/show_page_number" />
 
+    <com.google.android.material.switchmaterial.SwitchMaterial
+        android:id="@+id/dual_page_split"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:text="@string/pref_dual_page_split"
+        android:textColor="?android:attr/textColorSecondary"
+        app:layout_constraintTop_toBottomOf="@id/fullscreen" />
+
     <com.google.android.material.switchmaterial.SwitchMaterial
         android:id="@+id/cutout_short"
         android:layout_width="match_parent"
@@ -158,7 +166,7 @@
         android:text="@string/pref_cutout_short"
         android:textColor="?android:attr/textColorSecondary"
         android:visibility="gone"
-        app:layout_constraintTop_toBottomOf="@id/fullscreen"
+        app:layout_constraintTop_toBottomOf="@id/dual_page_split"
         tools:visibility="visible" />
 
     <com.google.android.material.switchmaterial.SwitchMaterial

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

@@ -250,6 +250,7 @@
 
       <!-- Reader section -->
     <string name="pref_fullscreen">Fullscreen</string>
+    <string name="pref_dual_page_split">Dual page split (ALPHA)</string>
     <string name="pref_cutout_short">Show content in cutout area</string>
     <string name="pref_lock_orientation">Lock orientation</string>
     <string name="pref_page_transitions">Animate page transitions</string>