Remove RxJava in PageHolder (#9103)

Inline readImageHeaderSubscription in PageHolder

Inline readImageHeaderSubscription in PagerPageHolder and
WebtoonPageHolder by converting setImage() into a suspend function.
The image processing runs in the loadPageAndProcessStatus
continuation.

Use suspendCancellableCoroutine as a substitute for doOnUnsubscribe
in WebtoonPageHolder.
Closing openStream after the frame.setImage but before the PageHolder
is recycled causes the page display to fail for reasons that are not
currently understood.

Remove subscription handling from WebtoonViewer/WebtoonBaseHolder as
it is no longer used.

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

@@ -20,11 +20,9 @@ import kotlinx.coroutines.MainScope
 import kotlinx.coroutines.flow.collectLatest
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.supervisorScope
-import rx.Observable
-import rx.Subscription
-import rx.android.schedulers.AndroidSchedulers
-import rx.schedulers.Schedulers
 import tachiyomi.core.util.lang.launchIO
+import tachiyomi.core.util.lang.withIOContext
+import tachiyomi.core.util.lang.withUIContext
 import java.io.BufferedInputStream
 import java.io.ByteArrayInputStream
 import java.io.InputStream
@@ -66,12 +64,6 @@ class PagerPageHolder(
      */
     private var loadJob: Job? = null
 
-    /**
-     * Subscription used to read the header of the image. This is needed in order to instantiate
-     * the appropiate image view depending if the image is animated (GIF).
-     */
-    private var readImageHeaderSubscription: Subscription? = null
-
     init {
         addView(progressIndicator)
         loadJob = scope.launch { loadPageAndProcessStatus() }
@@ -85,7 +77,6 @@ class PagerPageHolder(
         super.onDetachedFromWindow()
         loadJob?.cancel()
         loadJob = null
-        unsubscribeReadImageHeader()
     }
 
     /**
@@ -119,14 +110,6 @@ class PagerPageHolder(
         }
     }
 
-    /**
-     * Unsubscribes from the read image header subscription.
-     */
-    private fun unsubscribeReadImageHeader() {
-        readImageHeaderSubscription?.unsubscribe()
-        readImageHeaderSubscription = null
-    }
-
     /**
      * Called when the page is queued.
      */
@@ -154,19 +137,16 @@ class PagerPageHolder(
     /**
      * Called when the page is ready.
      */
-    private fun setImage() {
+    private suspend fun setImage() {
         progressIndicator.setProgress(0)
         errorLayout?.root?.isVisible = false
 
-        unsubscribeReadImageHeader()
         val streamFn = page.stream ?: return
 
-        readImageHeaderSubscription = Observable
-            .fromCallable {
-                val stream = streamFn().buffered(16)
-                val itemStream = process(item, stream)
+        val (bais, isAnimated, background) = withIOContext {
+            streamFn().buffered(16).use { stream ->
+                process(item, stream).use { itemStream ->
                     val bais = ByteArrayInputStream(itemStream.readBytes())
-                try {
                     val isAnimated = ImageUtil.isAnimatedAndSupported(bais)
                     bais.reset()
                     val background = if (!isAnimated && viewer.config.automaticBackground) {
@@ -176,14 +156,10 @@ class PagerPageHolder(
                     }
                     bais.reset()
                     Triple(bais, isAnimated, background)
-                } finally {
-                    stream.close()
-                    itemStream.close()
                 }
             }
-            .subscribeOn(Schedulers.io())
-            .observeOn(AndroidSchedulers.mainThread())
-            .doOnNext { (bais, isAnimated, background) ->
+        }
+        withUIContext {
             bais.use {
                 setImage(
                     it,
@@ -201,7 +177,6 @@ class PagerPageHolder(
                 }
             }
         }
-            .subscribe({}, {})
     }
 
     private fun process(page: ReaderPage, imageStream: BufferedInputStream): InputStream {

app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/webtoon/WebtoonBaseHolder.kt

@@ -4,7 +4,6 @@ import android.content.Context
 import android.view.View
 import android.view.ViewGroup.LayoutParams
 import androidx.recyclerview.widget.RecyclerView
-import rx.Subscription
 
 abstract class WebtoonBaseHolder(
     view: View,
@@ -21,21 +20,6 @@ abstract class WebtoonBaseHolder(
      */
     open fun recycle() {}
 
-    /**
-     * Adds a subscription to a list of subscriptions that will automatically unsubscribe when the
-     * activity or the reader is destroyed.
-     */
-    protected fun addSubscription(subscription: Subscription?) {
-        viewer.subscriptions.add(subscription)
-    }
-
-    /**
-     * Removes a subscription from the list of subscriptions.
-     */
-    protected fun removeSubscription(subscription: Subscription?) {
-        subscription?.let { viewer.subscriptions.remove(it) }
-    }
-
     /**
      * Extension method to set layout params to wrap content on this view.
      */

app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/webtoon/WebtoonPageHolder.kt

@@ -25,11 +25,10 @@ import kotlinx.coroutines.MainScope
 import kotlinx.coroutines.flow.collectLatest
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.supervisorScope
-import rx.Observable
-import rx.Subscription
-import rx.android.schedulers.AndroidSchedulers
-import rx.schedulers.Schedulers
+import kotlinx.coroutines.suspendCancellableCoroutine
 import tachiyomi.core.util.lang.launchIO
+import tachiyomi.core.util.lang.withIOContext
+import tachiyomi.core.util.lang.withUIContext
 import java.io.BufferedInputStream
 import java.io.InputStream
 
@@ -79,12 +78,6 @@ class WebtoonPageHolder(
      */
     private var loadJob: Job? = null
 
-    /**
-     * Subscription used to read the header of the image. This is needed in order to instantiate
-     * the appropriate image view depending if the image is animated (GIF).
-     */
-    private var readImageHeaderSubscription: Subscription? = null
-
     init {
         refreshLayoutParams()
 
@@ -121,7 +114,6 @@ class WebtoonPageHolder(
     override fun recycle() {
         loadJob?.cancel()
         loadJob = null
-        unsubscribeReadImageHeader()
 
         removeErrorLayout()
         frame.recycle()
@@ -159,14 +151,6 @@ class WebtoonPageHolder(
         }
     }
 
-    /**
-     * Unsubscribes from the read image header subscription.
-     */
-    private fun unsubscribeReadImageHeader() {
-        removeSubscription(readImageHeaderSubscription)
-        readImageHeaderSubscription = null
-    }
-
     /**
      * Called when the page is queued.
      */
@@ -197,26 +181,22 @@ class WebtoonPageHolder(
     /**
      * Called when the page is ready.
      */
-    private fun setImage() {
+    private suspend fun setImage() {
         progressIndicator.setProgress(0)
         removeErrorLayout()
 
-        unsubscribeReadImageHeader()
         val streamFn = page?.stream ?: return
 
-        var openStream: InputStream? = null
-        readImageHeaderSubscription = Observable
-            .fromCallable {
+        val (openStream, isAnimated) = withIOContext {
             val stream = streamFn().buffered(16)
-                openStream = process(stream)
+            val openStream = process(stream)
 
-                ImageUtil.isAnimatedAndSupported(stream)
+            val isAnimated = ImageUtil.isAnimatedAndSupported(stream)
+            Pair(openStream, isAnimated)
         }
-            .subscribeOn(Schedulers.io())
-            .observeOn(AndroidSchedulers.mainThread())
-            .doOnNext { isAnimated ->
+        withUIContext {
             frame.setImage(
-                    openStream!!,
+                openStream,
                 isAnimated,
                 ReaderPageImageView.Config(
                     zoomDuration = viewer.config.doubleTapAnimDuration,
@@ -225,12 +205,10 @@ class WebtoonPageHolder(
                 ),
             )
         }
-            // Keep the Rx stream alive to close the input stream only when unsubscribed
-            .flatMap { Observable.never<Unit>() }
-            .doOnUnsubscribe { openStream?.close() }
-            .subscribe({}, {})
-
-        addSubscription(readImageHeaderSubscription)
+        // Suspend the coroutine to close the input stream only when the WebtoonPageHolder is recycled
+        suspendCancellableCoroutine<Nothing> { continuation ->
+            continuation.invokeOnCancellation { openStream.close() }
+        }
     }
 
     private fun process(imageStream: BufferedInputStream): InputStream {

app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/webtoon/WebtoonViewer.kt

@@ -22,7 +22,6 @@ import eu.kanade.tachiyomi.ui.reader.viewer.BaseViewer
 import eu.kanade.tachiyomi.ui.reader.viewer.ViewerNavigation.NavigationRegion
 import kotlinx.coroutines.MainScope
 import kotlinx.coroutines.cancel
-import rx.subscriptions.CompositeSubscription
 import tachiyomi.core.util.system.logcat
 import uy.kohesive.injekt.Injekt
 import uy.kohesive.injekt.api.get
@@ -74,11 +73,6 @@ class WebtoonViewer(val activity: ReaderActivity, val isContinuous: Boolean = tr
      */
     private var currentPage: Any? = null
 
-    /**
-     * Subscriptions to keep while this viewer is used.
-     */
-    val subscriptions = CompositeSubscription()
-
     private val threshold: Int =
         Injekt.get<ReaderPreferences>()
             .readerHideThreshold()
@@ -196,7 +190,6 @@ class WebtoonViewer(val activity: ReaderActivity, val isContinuous: Boolean = tr
     override fun destroy() {
         super.destroy()
         scope.cancel()
-        subscriptions.unsubscribe()
     }
 
     /**