Add select all menu option for library category

Based on https://github.com/Jays2Kings/tachiyomiJ2K/commit/ae5ad2a9a6fa3a4f2139712564a0b561ed00b37a

app/src/main/java/eu/kanade/tachiyomi/ui/library/LibraryCategoryView.kt

@@ -124,6 +124,15 @@ class LibraryCategoryView @JvmOverloads constructor(context: Context, attrs: Att
 
         subscriptions += controller.selectionRelay
                 .subscribe { onSelectionChanged(it) }
+
+        subscriptions += controller.selectAllRelay
+                .filter { it == category.id }
+                .subscribe {
+                    adapter.currentItems.forEach { item ->
+                        controller.setSelection(item.manga, true)
+                    }
+                    controller.invalidateActionMode()
+                }
     }
 
     fun onRecycle() {

app/src/main/java/eu/kanade/tachiyomi/ui/library/LibraryController.kt

@@ -94,6 +94,11 @@ class LibraryController(
      */
     val libraryMangaRelay: BehaviorRelay<LibraryMangaEvent> = BehaviorRelay.create()
 
+    /**
+     * Relay to notify the library's viewpager to select all manga
+     */
+    val selectAllRelay: PublishRelay<Int> = PublishRelay.create()
+
     /**
      * Number of manga per row in grid mode.
      */
@@ -409,6 +414,7 @@ class LibraryController(
             }
             R.id.action_move_to_category -> showChangeMangaCategoriesDialog()
             R.id.action_delete -> showDeleteMangaDialog()
+            R.id.action_select_all -> selectAllCategoryManga()
             else -> return false
         }
         return true
@@ -496,6 +502,12 @@ class LibraryController(
         }
     }
 
+    private fun selectAllCategoryManga() {
+        adapter?.categories?.getOrNull(library_pager.currentItem)?.id?.let {
+            selectAllRelay.call(it)
+        }
+    }
+
     override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
         if (requestCode == REQUEST_IMAGE_OPEN) {
             if (data == null || resultCode != Activity.RESULT_OK) return

app/src/main/res/menu/library_selection.xml

@@ -18,4 +18,9 @@
           android:icon="@drawable/ic_delete_white_24dp"
           app:showAsAction="ifRoom"/>
 
-</menu>
+    <item android:id="@+id/action_select_all"
+        android:title="@string/action_select_all"
+        android:icon="@drawable/ic_select_all_white_24dp"
+        app:showAsAction="ifRoom"/>
+
+</menu>