fix: avoid ANR during live text style updates

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

@@ -223,6 +223,16 @@ class ReaderActivity : BaseActivity() {
                     ReaderViewModel.Event.ReloadViewerChapters -> {
                         viewModel.state.value.viewerChapters?.let(::setChapters)
                     }
+                    ReaderViewModel.Event.RefreshCurrentTextPage -> {
+                        viewModel.state.value.viewer?.refreshCurrentPage()
+                    }
+                    ReaderViewModel.Event.ReloadTextViewerChapters -> {
+                        val state = viewModel.state.value
+                        val chapters = state.viewerChapters
+                        if (chapters != null) {
+                            state.viewer?.refreshTextChapters(chapters)
+                        }
+                    }
                     ReaderViewModel.Event.PageChanged -> {
                         displayRefreshHost.flash()
                     }
@@ -254,7 +264,8 @@ class ReaderActivity : BaseActivity() {
                 readerState = viewModel.state,
                 onChangeReadingMode = viewModel::setMangaReadingMode,
                 onChangeOrientation = viewModel::setMangaOrientationType,
-                onTextSettingsChanged = viewModel::reloadTextReaderStyle,
+                onTextSettingsPreview = viewModel::previewTextReaderStyle,
+                onTextSettingsCommit = viewModel::commitTextReaderStyle,
                 preferences = readerPreferences,
             )
         }

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

@@ -40,6 +40,7 @@ import eu.kanade.tachiyomi.source.model.Page
 import eu.kanade.tachiyomi.source.online.HttpSource
 import eu.kanade.tachiyomi.ui.reader.loader.ChapterLoader
 import eu.kanade.tachiyomi.ui.reader.loader.DownloadPageLoader
+import eu.kanade.tachiyomi.ui.reader.loader.TextReaderPage
 import eu.kanade.tachiyomi.ui.reader.model.InsertPage
 import eu.kanade.tachiyomi.ui.reader.model.ReaderChapter
 import eu.kanade.tachiyomi.ui.reader.model.ReaderPage
@@ -56,6 +57,7 @@ import eu.kanade.tachiyomi.util.storage.DiskUtil
 import eu.kanade.tachiyomi.util.storage.cacheImageDir
 import kotlinx.coroutines.CancellationException
 import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.delay
 import kotlinx.coroutines.channels.Channel
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.asStateFlow
@@ -90,7 +92,6 @@ import tachiyomi.domain.source.service.SourceManager
 import tachiyomi.source.local.image.LocalCoverManager
 import tachiyomi.source.local.isLocal
 import java.util.Date
-import java.util.concurrent.atomic.AtomicBoolean
 import kotlin.math.roundToInt
 import kotlin.time.Clock
 
@@ -824,41 +825,36 @@ class ReaderViewModel(
         mutableState.update { it.copy(dialog = null) }
     }
 
-    private val textReaderStyleReloading = AtomicBoolean(false)
-    private val textReaderStyleReloadPending = AtomicBoolean(false)
-
-    fun reloadTextReaderStyle() {
+    fun previewTextReaderStyle() {
         val chapter = state.value.currentChapter ?: return
         if (chapter.pageLoader?.usesTextReaderStyle != true) return
+        val style = readerPreferences.textReaderStyle()
+        val textPages = chapter.pages?.filterIsInstance<TextReaderPage>().orEmpty()
+        if (textPages.isEmpty()) return
+
+        textPages.forEach { it.updateStyle(style) }
+        eventChannel.trySend(Event.RefreshCurrentTextPage)
+    }
+
+    fun commitTextReaderStyle() {
+        val chapter = state.value.currentChapter ?: return
+        if (chapter.pageLoader?.usesTextReaderStyle != true) return
+        if (chapter.pages?.any { it is TextReaderPage } != true) return
         val chapterLoader = loader ?: return
-
-        if (!textReaderStyleReloading.compareAndSet(false, true)) {
-            textReaderStyleReloadPending.set(true)
-            return
-        }
-
         val requestedPage = (state.value.currentPage - 1).coerceAtLeast(0)
         val oldLastIndex = (chapter.pages?.lastIndex ?: 0).coerceAtLeast(0)
         val readingProgress = if (oldLastIndex == 0) 0f else requestedPage.toFloat() / oldLastIndex
 
         viewModelScope.launchIO {
             try {
-                chapter.pageLoader?.recycle()
-                chapter.pageLoader = null
-                chapter.state = ReaderChapter.State.Wait
-                chapter.requestedPage = requestedPage
-                chapterLoader.loadChapter(chapter)
-                val newLastIndex = (chapter.pages?.lastIndex ?: 0).coerceAtLeast(0)
-                chapter.requestedPage = (readingProgress * newLastIndex).roundToInt().coerceIn(0, newLastIndex)
-                eventChannel.send(Event.ReloadViewerChapters)
+                val oldLoader = chapterLoader.reloadTextChapter(chapter, readingProgress) ?: return@launchIO
+                eventChannel.send(Event.ReloadTextViewerChapters)
+                // Give old visible holders time to detach before closing resources such as EpubReader.
+                delay(2000)
+                oldLoader.recycle()
             } catch (e: Throwable) {
                 if (e is CancellationException) throw e
-                logcat(LogPriority.ERROR, e) { "Failed to reload text reader style" }
-            } finally {
-                textReaderStyleReloading.set(false)
-                if (textReaderStyleReloadPending.getAndSet(false)) {
-                    reloadTextReaderStyle()
-                }
+                logcat(LogPriority.ERROR, e) { "Failed to repaginate text reader style" }
             }
         }
     }
@@ -1052,6 +1048,8 @@ class ReaderViewModel(
 
     sealed interface Event {
         data object ReloadViewerChapters : Event
+        data object RefreshCurrentTextPage : Event
+        data object ReloadTextViewerChapters : Event
         data object PageChanged : Event
         data class SetOrientation(val orientation: Int) : Event
         data class SetCoverResult(val result: SetAsCoverResult) : Event

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

@@ -22,6 +22,7 @@ import tachiyomi.domain.source.model.StubSource
 import tachiyomi.i18n.MR
 import tachiyomi.source.local.LocalSource
 import tachiyomi.source.local.io.Format
+import kotlin.math.roundToInt
 
 /**
  * Loader used to retrieve the [PageLoader] for a given chapter.
@@ -73,6 +74,36 @@ class ChapterLoader(
         }
     }
 
+
+    suspend fun reloadTextChapter(chapter: ReaderChapter, readingProgress: Float): PageLoader? {
+        return withIOContext {
+            val newLoader = getPageLoader(chapter)
+            if (!newLoader.usesTextReaderStyle) {
+                newLoader.recycle()
+                return@withIOContext null
+            }
+
+            try {
+                val pages = newLoader.getPages()
+                    .onEach { it.chapter = chapter }
+                if (pages.isEmpty()) {
+                    throw Exception(context.stringResource(MR.strings.page_list_empty_error))
+                }
+
+                val oldLoader = chapter.pageLoader
+                chapter.pageLoader = newLoader
+                chapter.requestedPage = (readingProgress * pages.lastIndex)
+                    .roundToInt()
+                    .coerceIn(0, pages.lastIndex)
+                chapter.state = ReaderChapter.State.Loaded(pages)
+                oldLoader
+            } catch (e: Throwable) {
+                newLoader.recycle()
+                throw e
+            }
+        }
+    }
+
     /**
      * Checks [chapter] to be loaded based on present pages and loader in addition to state.
      */

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

@@ -26,10 +26,7 @@ internal class EpubPageLoader(
 
         if (textPages.isNotEmpty()) {
             return textPages.mapIndexed { index, text ->
-                ReaderPage(index).apply {
-                    stream = { TextPageRenderer.render(text, style) }
-                    status = Page.State.Ready
-                }
+                TextReaderPage(index, text, style)
             }
         }
 

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

@@ -1,7 +1,6 @@
 package eu.kanade.tachiyomi.ui.reader.loader
 
 import com.hippo.unifile.UniFile
-import eu.kanade.tachiyomi.source.model.Page
 import eu.kanade.tachiyomi.ui.reader.model.ReaderPage
 import eu.kanade.tachiyomi.ui.reader.setting.TextReaderStyle
 import java.nio.ByteBuffer
@@ -22,10 +21,7 @@ internal class TextPageLoader(
         val bytes = file.openInputStream().use { it.readBytes() }
         val text = decodeText(bytes)
         return TextPageRenderer.paginate(text, style).mapIndexed { index, pageText ->
-            ReaderPage(index).apply {
-                stream = { TextPageRenderer.render(pageText, style) }
-                status = Page.State.Ready
-            }
+            TextReaderPage(index, pageText, style)
         }
     }
 

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

@@ -0,0 +1,29 @@
+package eu.kanade.tachiyomi.ui.reader.loader
+
+import eu.kanade.tachiyomi.source.model.Page
+import eu.kanade.tachiyomi.ui.reader.model.ReaderPage
+import eu.kanade.tachiyomi.ui.reader.setting.TextReaderStyle
+
+/**
+ * A rendered text page whose style can be changed without rebuilding the chapter.
+ * Page boundaries remain stable during the live preview; a full repagination is done
+ * once when the settings dialog is dismissed.
+ */
+internal class TextReaderPage(
+    index: Int,
+    private val pageText: String,
+    initialStyle: TextReaderStyle,
+) : ReaderPage(index) {
+
+    @Volatile
+    private var style: TextReaderStyle = initialStyle
+
+    init {
+        stream = { TextPageRenderer.render(pageText, style) }
+        status = Page.State.Ready
+    }
+
+    fun updateStyle(newStyle: TextReaderStyle) {
+        style = newStyle
+    }
+}

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

@@ -16,7 +16,8 @@ class ReaderSettingsViewModel(
     readerState: StateFlow<ReaderViewModel.State>,
     val onChangeReadingMode: (ReadingMode) -> Unit,
     val onChangeOrientation: (ReaderOrientation) -> Unit,
-    private val onTextSettingsChanged: () -> Unit,
+    private val onTextSettingsPreview: () -> Unit,
+    private val onTextSettingsCommit: () -> Unit,
     val preferences: ReaderPreferences,
 ) : ViewModel() {
 
@@ -31,20 +32,24 @@ class ReaderSettingsViewModel(
         .stateIn(viewModelScope, SharingStarted.Lazily, null)
 
     private var textSettingsReloadJob: Job? = null
+    private var textSettingsDirty = false
 
     fun requestTextSettingsReload() {
+        textSettingsDirty = true
         textSettingsReloadJob?.cancel()
         textSettingsReloadJob = viewModelScope.launch {
-            delay(150)
-            onTextSettingsChanged()
+            delay(100)
+            onTextSettingsPreview()
             textSettingsReloadJob = null
         }
     }
 
     fun flushTextSettingsReload() {
-        if (textSettingsReloadJob == null) return
+        if (!textSettingsDirty) return
         textSettingsReloadJob?.cancel()
         textSettingsReloadJob = null
-        onTextSettingsChanged()
+        onTextSettingsPreview()
+        textSettingsDirty = false
+        onTextSettingsCommit()
     }
 }

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

@@ -26,6 +26,14 @@ interface Viewer {
      */
     fun setChapters(chapters: ViewerChapters)
 
+    /** Rebinds only the currently visible page(s), used for lightweight text-style preview. */
+    fun refreshCurrentPage() {}
+
+    /** Replaces repaginated text pages without expensive per-item diffing where possible. */
+    fun refreshTextChapters(chapters: ViewerChapters) {
+        setChapters(chapters)
+    }
+
     /**
      * Tells this viewer to move to the given [page].
      */

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

@@ -380,6 +380,17 @@ abstract class PagerViewer(val activity: ReaderActivity) : Viewer {
         pager.setCurrentItem(currentItem, false)
     }
 
+    override fun refreshCurrentPage() {
+        refreshAdapter()
+    }
+
+    override fun refreshTextChapters(chapters: ViewerChapters) {
+        setChaptersInternal(chapters)
+        val pages = chapters.currChapter.pages ?: return
+        val page = pages[min(chapters.currChapter.requestedPage, pages.lastIndex)]
+        moveToPage(page)
+    }
+
     /**
      * Called from the containing activity when a key [event] is received. It should return true
      * if the event was handled, false otherwise.

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

@@ -35,7 +35,7 @@ class WebtoonAdapter(val viewer: WebtoonViewer) : RecyclerView.Adapter<RecyclerV
      * Updates this adapter with the given [chapters]. It handles setting a few pages of the
      * next/previous chapter to allow seamless transitions.
      */
-    fun setChapters(chapters: ViewerChapters, forceTransition: Boolean) {
+    fun setChapters(chapters: ViewerChapters, forceTransition: Boolean, useDiff: Boolean = true) {
         val newItems = mutableListOf<Any>()
 
         // Forces chapter transition if there is missing chapters
@@ -65,13 +65,18 @@ class WebtoonAdapter(val viewer: WebtoonViewer) : RecyclerView.Adapter<RecyclerV
 
         chapters.nextChapter?.pages?.let(newItems::addAll)
 
-        updateItems(newItems)
+        updateItems(newItems, useDiff)
     }
 
-    private fun updateItems(newItems: List<Any>) {
-        val result = DiffUtil.calculateDiff(Callback(items, newItems))
-        items = newItems
-        result.dispatchUpdatesTo(this)
+    private fun updateItems(newItems: List<Any>, useDiff: Boolean) {
+        if (useDiff) {
+            val result = DiffUtil.calculateDiff(Callback(items, newItems))
+            items = newItems
+            result.dispatchUpdatesTo(this)
+        } else {
+            items = newItems
+            notifyDataSetChanged()
+        }
     }
 
     fun refresh() {

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

@@ -353,6 +353,19 @@ class WebtoonViewer(val activity: ReaderActivity, val isContinuous: Boolean = tr
             min(position + 3, adapter.itemCount - 1),
         )
     }
+
+    override fun refreshCurrentPage() {
+        refreshAdapter()
+    }
+
+    override fun refreshTextChapters(chapters: ViewerChapters) {
+        val forceTransition = config.alwaysShowChapterTransition || currentPage is ChapterTransition
+        adapter.setChapters(chapters, forceTransition, useDiff = false)
+        val pages = chapters.currChapter.pages ?: return
+        val page = pages[min(chapters.currChapter.requestedPage, pages.lastIndex)]
+        moveToPage(page)
+        currentPage = page
+    }
 }
 
 // Double the cache size to reduce rebinds/recycles incurred by the extra layout space on scroll direction changes