Add Reader Page Preload option

Based on jobobby04@68bfba4

Closes #544

Co-Authored-By: jobobby04 <17078382+jobobby04@users.noreply.github.com>

app/src/main/java/eu/kanade/tachiyomi/data/cache/ChapterCache.kt

@@ -6,9 +6,15 @@ import com.github.salomonbrys.kotson.fromJson
 import com.google.gson.Gson
 import com.jakewharton.disklrucache.DiskLruCache
 import eu.kanade.tachiyomi.data.database.models.Chapter
+import eu.kanade.tachiyomi.data.preference.PreferencesHelper
 import eu.kanade.tachiyomi.source.model.Page
 import eu.kanade.tachiyomi.util.storage.DiskUtil
 import eu.kanade.tachiyomi.util.storage.saveTo
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.flow.launchIn
+import kotlinx.coroutines.flow.onEach
 import okhttp3.Response
 import okio.buffer
 import okio.sink
@@ -16,6 +22,8 @@ import rx.Observable
 import uy.kohesive.injekt.injectLazy
 import java.io.File
 import java.io.IOException
+import kotlin.math.pow
+import kotlin.math.roundToLong
 
 /**
  * Class used to create chapter cache
@@ -39,19 +47,18 @@ class ChapterCache(private val context: Context) {
         const val PARAMETER_VALUE_COUNT = 1
 
         /** The maximum number of bytes this cache should use to store.  */
-        const val PARAMETER_CACHE_SIZE = 75L * 1024 * 1024
+        const val PARAMETER_CACHE_SIZE = 50L * 1024 * 1024
     }
 
     /** Google Json class used for parsing JSON files.  */
     private val gson: Gson by injectLazy()
 
+    private val preferences: PreferencesHelper by injectLazy()
+
+    private val scope = CoroutineScope(Job() + Dispatchers.IO)
+
     /** Cache class used for cache management.  */
-    private val diskCache = DiskLruCache.open(
+    private var diskCache = setupDiskCache(preferences.preloadSize().get())
-        File(context.cacheDir, PARAMETER_CACHE_DIRECTORY),
-        PARAMETER_APP_VERSION,
-        PARAMETER_VALUE_COUNT,
-        PARAMETER_CACHE_SIZE
-    )
 
     /**
      * Returns directory of cache.
@@ -71,6 +78,27 @@ class ChapterCache(private val context: Context) {
     val readableSize: String
         get() = Formatter.formatFileSize(context, realSize)
 
+    init {
+        preferences.preloadSize().asFlow()
+            .onEach {
+                // Save old cache for destruction later
+                val oldCache = diskCache
+                diskCache = setupDiskCache(it)
+                oldCache.close()
+            }
+            .launchIn(scope)
+    }
+
+    private fun setupDiskCache(cacheSize: Int): DiskLruCache {
+        return DiskLruCache.open(
+            File(context.cacheDir, PARAMETER_CACHE_DIRECTORY),
+            PARAMETER_APP_VERSION,
+            PARAMETER_VALUE_COUNT,
+            // 4 pages = 115MB, 6 = ~150MB, 10 = ~200MB, 20 = ~300MB
+            (PARAMETER_CACHE_SIZE * cacheSize.toFloat().pow(0.6f)).roundToLong()
+        )
+    }
+
     /**
      * Remove file from cache.
      *

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

@@ -70,6 +70,8 @@ object PreferenceKeys {
     const val showNavigationOverlayNewUser = "reader_navigation_overlay_new_user"
     const val showNavigationOverlayNewUserWebtoon = "reader_navigation_overlay_new_user_webtoon"
 
+    const val preloadSize = "preload_size"
+
     const val webtoonSidePadding = "webtoon_side_padding"
 
     const val webtoonEnableZoomOut = "webtoon_enable_zoom_out"

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

@@ -151,6 +151,8 @@ class PreferencesHelper(val context: Context) {
 
     fun showNavigationOverlayNewUserWebtoon() = flowPrefs.getBoolean(Keys.showNavigationOverlayNewUserWebtoon, true)
 
+    fun preloadSize() = flowPrefs.getInt(Keys.preloadSize, 6)
+
     fun updateOnlyNonCompleted() = prefs.getBoolean(Keys.updateOnlyNonCompleted, false)
 
     fun autoUpdateTrack() = prefs.getBoolean(Keys.autoUpdateTrack, true)

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

@@ -10,6 +10,12 @@ import eu.kanade.tachiyomi.ui.reader.model.ReaderPage
 import eu.kanade.tachiyomi.ui.reader.viewer.pager.PagerPageHolder
 import eu.kanade.tachiyomi.util.lang.plusAssign
 import eu.kanade.tachiyomi.util.system.ImageUtil
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.cancel
+import kotlinx.coroutines.flow.launchIn
+import kotlinx.coroutines.flow.onEach
 import rx.Completable
 import rx.Observable
 import rx.schedulers.Schedulers
@@ -41,9 +47,16 @@ class HttpPageLoader(
     private val subscriptions = CompositeSubscription()
 
     private val preferences by injectLazy<PreferencesHelper>()
-    private val preloadSize = 4
+    private var preloadSize = preferences.preloadSize().get()
 
+    private val scope = CoroutineScope(Job() + Dispatchers.IO)
     init {
+        // Adding flow since we can reach reader settings after this is created
+        preferences.preloadSize().asFlow()
+            .onEach {
+                preloadSize = it
+            }
+            .launchIn(scope)
         subscriptions += Observable.defer { Observable.just(queue.take().page) }
             .filter { it.status == Page.QUEUE }
             .concatMap { source.fetchImageFromCacheThenNet(it) }
@@ -65,6 +78,7 @@ class HttpPageLoader(
      */
     override fun recycle() {
         super.recycle()
+        scope.cancel()
         subscriptions.unsubscribe()
         queue.clear()
 

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

@@ -57,6 +57,14 @@ class SettingsReaderController : SettingsController() {
                     defaultValue = false
                 }
             }
+            intListPreference(activity) {
+                key = Keys.preloadSize
+                titleRes = R.string.page_preload_amount
+                entryValues = listOf(4, 6, 8, 10, 12, 14, 16, 20)
+                entries = entryValues.map { context.resources.getQuantityString(R.plurals.pages_plural, it, it) }
+                defaultValue = 6
+                summaryRes = R.string.amount_of_pages_to_preload
+            }
         }
 
         preferenceCategory {

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

@@ -330,6 +330,8 @@
     <string name="double_tap_anim_speed">Double tap animation speed</string>
     <string name="show_page_number">Show page number</string>
     <string name="true_32bit_color">32-bit color</string>
+    <string name="page_preload_amount">Page preload amount</string>
+    <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="crop_borders">Crop borders</string>
@@ -406,6 +408,11 @@
     <string name="page_layout">Page layout</string>
     <string name="automatic_can_still_switch">While using automatic page layout, you can still switch between layouts while reading without overriding this setting</string>
     <string name="automatic_orientation">Automatic (based on orientation)</string>
+    <plurals name="pages_plural">
+        <item quantity="one">%1$d page</item>
+        <item quantity="other">%1$d pages</item>
+    </plurals>
+
 
     <!-- Manga details -->
     <string name="about_this_">About this %1$s</string>