Improve live text reader repagination

app/build.gradle.kts

@@ -216,6 +216,7 @@ dependencies {
     implementation(projects.coreMetadata)
     implementation(projects.sourceApi)
     implementation(projects.sourceLocal)
+    implementation(libs.jsoup)
     implementation(projects.data)
     implementation(projects.domain)
     implementation(projects.presentationCore)

app/src/main/java/eu/kanade/presentation/reader/settings/GeneralSettingsPage.kt

@@ -51,7 +51,10 @@ internal fun ColumnScope.GeneralPage(viewModel: ReaderSettingsViewModel) {
         themes.map { (labelRes, value) ->
             FilterChip(
                 selected = readerTheme == value,
-                onClick = { viewModel.preferences.readerTheme.set(value) },
+                onClick = {
+                    viewModel.preferences.readerTheme.set(value)
+                    viewModel.requestTextAppearanceReload()
+                },
                 label = { Text(stringResource(labelRes)) },
             )
         }

app/src/main/java/eu/kanade/presentation/reader/settings/ReaderSettingsDialog.kt

@@ -9,7 +9,6 @@ import androidx.compose.foundation.rememberScrollState
 import androidx.compose.foundation.verticalScroll
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.LaunchedEffect
-import androidx.compose.runtime.remember
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.platform.LocalView
 import androidx.compose.ui.window.DialogWindowProvider
@@ -33,15 +32,11 @@ fun ReaderSettingsDialog(
         stringResource(MR.strings.pref_category_text_reader),
     )
     val pagerState = rememberPagerState { tabTitles.size }
-    val initialTextStyle = remember { viewModel.preferences.textReaderStyle() }
-
     BoxWithConstraints {
         TabbedDialog(
             modifier = Modifier.heightIn(max = maxHeight * 0.75f),
             onDismissRequest = {
-                if (viewModel.preferences.textReaderStyle() != initialTextStyle) {
-                    viewModel.onTextSettingsChanged()
-                }
+                viewModel.flushTextSettingsReload()
                 onDismissRequest()
                 onShowMenus()
             },
@@ -51,7 +46,7 @@ fun ReaderSettingsDialog(
             val window = (LocalView.current.parent as? DialogWindowProvider)?.window
 
             LaunchedEffect(pagerState.currentPage) {
-                if (pagerState.currentPage == 2) {
+                if (pagerState.currentPage == 2 || pagerState.currentPage == 3) {
                     window?.setDimAmount(0f)
                     onHideMenus()
                 } else {

app/src/main/java/eu/kanade/presentation/reader/settings/TextSettingsPage.kt

@@ -31,10 +31,13 @@ internal fun ColumnScope.TextSettingsPage(viewModel: ReaderSettingsViewModel) {
     SliderItem(
         label = stringResource(MR.strings.pref_text_reader_font_size),
         value = fontSize,
-        valueRange = 32..72,
+        valueRange = 10..30,
         steps = 19,
-        valueString = fontSize.toString(),
-        onChange = fontSizePref::set,
+        valueString = "$fontSize sp",
+        onChange = { value ->
+            fontSizePref.set(value)
+            viewModel.requestTextSettingsReload()
+        },
         pillColor = MaterialTheme.colorScheme.surfaceContainerHighest,
     )
 
@@ -45,8 +48,11 @@ internal fun ColumnScope.TextSettingsPage(viewModel: ReaderSettingsViewModel) {
         value = lineSpacing,
         valueRange = 90..180,
         steps = 17,
-        valueString = "$lineSpacing%",
-        onChange = lineSpacingPref::set,
+        valueString = String.format("%.2fx", lineSpacing / 100f),
+        onChange = { value ->
+            lineSpacingPref.set(value)
+            viewModel.requestTextSettingsReload()
+        },
         pillColor = MaterialTheme.colorScheme.surfaceContainerHighest,
     )
 
@@ -55,10 +61,13 @@ internal fun ColumnScope.TextSettingsPage(viewModel: ReaderSettingsViewModel) {
     SliderItem(
         label = stringResource(MR.strings.pref_text_reader_paragraph_spacing),
         value = paragraphSpacing,
-        valueRange = 0..48,
-        steps = 11,
-        valueString = paragraphSpacing.toString(),
-        onChange = paragraphSpacingPref::set,
+        valueRange = 0..16,
+        steps = 15,
+        valueString = "$paragraphSpacing dp",
+        onChange = { value ->
+            paragraphSpacingPref.set(value)
+            viewModel.requestTextSettingsReload()
+        },
         pillColor = MaterialTheme.colorScheme.surfaceContainerHighest,
     )
 
@@ -68,7 +77,10 @@ internal fun ColumnScope.TextSettingsPage(viewModel: ReaderSettingsViewModel) {
         fontFamilies.forEach { (label, value) ->
             FilterChip(
                 selected = fontFamily == value,
-                onClick = { fontFamilyPref.set(value) },
+                onClick = {
+                    fontFamilyPref.set(value)
+                    viewModel.requestTextSettingsReload()
+                },
                 label = { Text(stringResource(label)) },
             )
         }

app/src/main/java/eu/kanade/tachiyomi/source/kavita/KavitaCompat.kt

@@ -0,0 +1,37 @@
+package eu.kanade.tachiyomi.source.kavita
+
+import eu.kanade.tachiyomi.source.Source
+
+private const val KAVITA_PACKAGE_PREFIX = "eu.kanade.tachiyomi.extension.all.kavita."
+
+internal fun Source.isKavitaSource(): Boolean =
+    this::class.java.name.startsWith(KAVITA_PACKAGE_PREFIX)
+
+/**
+ * Kavita extension chapter URLs are normally /Chapter/{id}. Keep compatibility
+ * with older/alternate forms used by reading lists and previous releases.
+ */
+internal fun String.toKavitaChapterId(): Int? {
+    Regex("""(?:^|/)Chapter/(\d+)""", RegexOption.IGNORE_CASE)
+        .find(this)
+        ?.groupValues
+        ?.getOrNull(1)
+        ?.toIntOrNull()
+        ?.let { return it }
+
+    Regex("""(?:^|/)chapter_(\d+)""", RegexOption.IGNORE_CASE)
+        .find(this)
+        ?.groupValues
+        ?.getOrNull(1)
+        ?.toIntOrNull()
+        ?.let { return it }
+
+    Regex("""[?&]chapterId=(\d+)""", RegexOption.IGNORE_CASE)
+        .find(this)
+        ?.groupValues
+        ?.getOrNull(1)
+        ?.toIntOrNull()
+        ?.let { return it }
+
+    return null
+}

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 +57,8 @@ 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.Job
+import kotlinx.coroutines.delay
 import kotlinx.coroutines.channels.Channel
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.asStateFlow
@@ -184,6 +187,12 @@ class ReaderViewModel(
      */
     private var loader: ChapterLoader? = null
 
+    /**
+     * Only the newest text repagination request is allowed to finish. Slider
+     * changes can arrive faster than a large TXT/EPUB chapter can be rebuilt.
+     */
+    private var textRepaginationJob: Job? = null
+
     /**
      * The time the chapter was started reading
      */
@@ -823,27 +832,45 @@ class ReaderViewModel(
         mutableState.update { it.copy(dialog = null) }
     }
 
-    fun reloadTextReaderStyle() {
+    fun previewTextReaderStyle() {
         val chapter = state.value.currentChapter ?: return
         if (chapter.pageLoader?.usesTextReaderStyle != true) return
-        val chapterLoader = loader ?: 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
+        val style = readerPreferences.textReaderStyle(context)
+        val textPages = chapter.pages?.filterIsInstance<TextReaderPage>().orEmpty()
+        if (textPages.isEmpty()) return
 
-        viewModelScope.launchIO {
+        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
+
+        val oldPageCount = chapter.pages?.size?.coerceAtLeast(1) ?: 1
+        val requestedPage = chapter.requestedPage.coerceIn(0, oldPageCount - 1)
+        // Anchor at the middle of the visible page so position remains stable
+        // when font size/spacing changes the total page count.
+        val readingProgress = ((requestedPage + 0.5f) / oldPageCount)
+            .coerceIn(0f, 0.999999f)
+
+        textRepaginationJob?.cancel()
+        textRepaginationJob = 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
+
+                // Resource cleanup must survive cancellation by the next slider value.
+                viewModelScope.launchNonCancellable {
+                    delay(750)
+                    oldLoader.recycle()
+                }
+
+                eventChannel.trySend(Event.ReloadTextViewerChapters)
             } catch (e: Throwable) {
                 if (e is CancellationException) throw e
-                logcat(LogPriority.ERROR, e) { "Failed to reload text reader style" }
+                logcat(LogPriority.ERROR, e) { "Failed to repaginate text reader style" }
             }
         }
     }
@@ -1037,6 +1064,8 @@ 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/BookOasisFilePageLoader.kt

@@ -34,9 +34,9 @@ internal class BookOasisFilePageLoader(
         val uniFile = UniFile.fromFile(file)
             ?: error("Unable to open cached BookOasis file: ${file.absolutePath}")
         val loader = when (ref.format) {
-            "epub" -> EpubPageLoader(uniFile.epubReader(context), textStyle)
+            "epub" -> EpubPageLoader(uniFile.epubReader(context), textStyle, context.cacheDir)
             "pdf" -> PdfPageLoader(context, uniFile)
-            "txt" -> TextPageLoader(uniFile, textStyle)
+            "txt" -> TextPageLoader(uniFile, textStyle, context.cacheDir)
             else -> error("Unsupported BookOasis document format: ${ref.format}")
         }
 

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

@@ -7,6 +7,8 @@ import eu.kanade.tachiyomi.data.download.DownloadProvider
 import eu.kanade.tachiyomi.source.Source
 import eu.kanade.tachiyomi.source.bookoasis.isBookOasisSource
 import eu.kanade.tachiyomi.source.bookoasis.toBookOasisChapterRef
+import eu.kanade.tachiyomi.source.kavita.isKavitaSource
+import eu.kanade.tachiyomi.source.kavita.toKavitaChapterId
 import eu.kanade.tachiyomi.source.online.HttpSource
 import eu.kanade.tachiyomi.ui.reader.model.ReaderChapter
 import eu.kanade.tachiyomi.ui.reader.setting.ReaderPreferences
@@ -20,6 +22,8 @@ import tachiyomi.domain.source.model.StubSource
 import tachiyomi.i18n.MR
 import tachiyomi.source.local.LocalSource
 import tachiyomi.source.local.io.Format
+import kotlinx.coroutines.currentCoroutineContext
+import kotlinx.coroutines.ensureActive
 
 /**
  * Loader used to retrieve the [PageLoader] for a given chapter.
@@ -71,6 +75,40 @@ 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))
+                }
+
+                // If a newer slider value cancelled this rebuild while getPages()
+                // was working, do not publish stale pages into the active chapter.
+                currentCoroutineContext().ensureActive()
+
+                val oldLoader = chapter.pageLoader
+                chapter.pageLoader = newLoader
+                chapter.requestedPage = (readingProgress.coerceIn(0f, 0.999999f) * pages.size)
+                    .toInt()
+                    .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.
      */
@@ -91,6 +129,7 @@ class ChapterLoader(
             source,
         )
         val bookOasisRef = dbChapter.url.toBookOasisChapterRef()
+        val kavitaChapterId = dbChapter.url.toKavitaChapterId()
 
         return when {
             isDownloaded -> DownloadPageLoader(
@@ -104,13 +143,23 @@ class ChapterLoader(
                 when (format) {
                     is Format.Directory -> DirectoryPageLoader(format.file)
                     is Format.Archive -> ArchivePageLoader(format.file.archiveReader(context))
-                    is Format.Epub -> EpubPageLoader(format.file.epubReader(context), readerPreferences.textReaderStyle())
+                    is Format.Epub -> EpubPageLoader(format.file.epubReader(context), readerPreferences.textReaderStyle(context), context.cacheDir)
                     is Format.Pdf -> PdfPageLoader(context, format.file)
-                    is Format.Text -> TextPageLoader(format.file, readerPreferences.textReaderStyle())
+                    is Format.Text -> TextPageLoader(format.file, readerPreferences.textReaderStyle(context), context.cacheDir)
                 }
             }
             source is HttpSource && source.isBookOasisSource() && bookOasisRef != null -> {
-                BookOasisFilePageLoader(context, source, bookOasisRef, readerPreferences.textReaderStyle())
+                BookOasisFilePageLoader(context, source, bookOasisRef, readerPreferences.textReaderStyle(context))
+            }
+            source is HttpSource && source.isKavitaSource() && kavitaChapterId != null -> {
+                KavitaCompatPageLoader(
+                    context = context,
+                    chapter = chapter,
+                    source = source,
+                    chapterCache = chapterCache,
+                    chapterId = kavitaChapterId,
+                    textStyle = readerPreferences.textReaderStyle(context),
+                )
             }
             source is HttpSource -> HttpPageLoader(chapter, source, chapterCache)
             source is StubSource -> error(context.stringResource(MR.strings.source_not_installed, source.toString()))

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

@@ -4,48 +4,144 @@ import eu.kanade.tachiyomi.source.model.Page
 import eu.kanade.tachiyomi.ui.reader.model.ReaderPage
 import eu.kanade.tachiyomi.ui.reader.setting.TextReaderStyle
 import mihon.core.archive.EpubReader
+import org.jsoup.Jsoup
+import java.io.File
+import java.io.InputStream
+import java.io.StringReader
 
 /**
  * Loader used to load a chapter from a .epub file.
  *
- * Text-based EPUBs are rendered as regular Mihon pages. Image-only EPUBs
- * keep the original image extraction behavior.
+ * Text-based EPUBs are rendered as regular Mihon pages. EPUB spine documents
+ * are processed one at a time so the full book text is never retained in heap.
+ * Image-only EPUBs keep the original image extraction behavior.
  */
 internal class EpubPageLoader(
     private val reader: EpubReader,
     private val style: TextReaderStyle,
+    private val cacheDir: File,
 ) : PageLoader() {
 
     override var isLocal: Boolean = true
     override val usesTextReaderStyle: Boolean = true
 
+    private var pageStore: TextPageStore? = null
+
     override suspend fun getPages(): List<ReaderPage> {
-        val textPages = reader.getTextFromPages()
-            .filter { it.isNotBlank() }
-            .flatMap { TextPageRenderer.paginate(it, style) }
+        check(!isRecycled)
 
+        pageStore?.close()
+        pageStore = null
+
+        val store = TextPageStore(cacheDir)
+        return try {
+            val textPages = buildTextPages(store)
             if (textPages.isNotEmpty()) {
-            return textPages.mapIndexed { index, text ->
-                ReaderPage(index).apply {
-                    stream = { TextPageRenderer.render(text, style) }
-                    status = Page.State.Ready
-                }
-            }
-        }
-
-        return reader.getImagesFromPages().mapIndexed { index, path ->
+                store.finishWriting()
+                pageStore = store
+                textPages
+            } else {
+                store.close()
+                reader.getImagesFromPages().mapIndexed { index, path ->
                     ReaderPage(index).apply {
                         stream = { reader.getInputStream(path)!! }
                         status = Page.State.Ready
                     }
                 }
             }
+        } catch (e: Throwable) {
+            store.close()
+            throw e
+        }
+    }
+
+    private fun buildTextPages(store: TextPageStore): MutableList<ReaderPage> {
+        val packageHref = reader.getPackageHref()
+        val packageDocument = reader.getPackageDocument(packageHref)
+        val manifest = packageDocument.select("manifest > item")
+            .filter { item ->
+                val mediaType = item.attr("media-type")
+                mediaType == "application/xhtml+xml" || mediaType == "text/html"
+            }
+            .associateBy { it.attr("id") }
+        val spine = packageDocument.select("spine > itemref")
+            .map { it.attr("idref") }
+
+        val result = mutableListOf<ReaderPage>()
+        spine.forEach { id ->
+            val href = manifest[id]?.attr("href").orEmpty()
+            if (href.isBlank()) return@forEach
+
+            openEntry(packageHref, href)?.use { input ->
+                val text = extractText(input)
+                if (text.isBlank()) return@use
+
+                StringReader(text).use { textReader ->
+                    TextPageRenderer.paginate(textReader, style) { pageText ->
+                        val ref = store.append(pageText)
+                        result += TextReaderPage(
+                            index = result.size,
+                            pageTextProvider = { store.read(ref) },
+                            initialStyle = style,
+                        )
+                    }
+                }
+            }
+        }
+        return result
+    }
+
+    private fun extractText(input: InputStream): String {
+        val pageDoc = Jsoup.parse(input, null, "")
+        pageDoc.select("br").append("\n")
+        pageDoc.select("p,div,li,h1,h2,h3,h4,h5,h6,blockquote").append("\n")
+        return pageDoc.body().wholeText()
+            ?.replace(Regex("[ \\t]+\\n"), "\n")
+            ?.replace(Regex("\\n{3,}"), "\n\n")
+            ?.trim()
+            .orEmpty()
+    }
+
+    private fun openEntry(packageHref: String, href: String): InputStream? {
+        val resolved = resolveEntryPath(packageHref, href)
+        val candidates = linkedSetOf(
+            resolved,
+            resolved.replace('\\', '/'),
+            resolved.replace('/', '\\'),
+        )
+        return candidates.firstNotNullOfOrNull { path ->
+            reader.getInputStream(path)
+        }
+    }
+
+    private fun resolveEntryPath(packageHref: String, href: String): String {
+        val relative = href
+            .substringBefore('#')
+            .substringBefore('?')
+            .trimStart('/', '\\')
+        val separator = if ('\\' in packageHref) '\\' else '/'
+        val base = packageHref.substringBeforeLast(separator, "")
+        val combined = if (base.isBlank()) relative else "$base$separator$relative"
+        val parts = combined.split('/', '\\')
+        val normalized = ArrayDeque<String>()
+
+        parts.forEach { part ->
+            when (part) {
+                "", "." -> Unit
+                ".." -> if (normalized.isNotEmpty()) normalized.removeLast()
+                else -> normalized.addLast(part)
+            }
+        }
+        return normalized.joinToString(separator.toString())
+    }
 
     override suspend fun loadPage(page: ReaderPage) {
         check(!isRecycled)
     }
 
     override fun recycle() {
+        pageStore?.close()
+        pageStore = null
         super.recycle()
         reader.close()
     }

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

@@ -0,0 +1,169 @@
+package eu.kanade.tachiyomi.ui.reader.loader
+
+import android.content.Context
+import com.hippo.unifile.UniFile
+import eu.kanade.tachiyomi.data.cache.ChapterCache
+import eu.kanade.tachiyomi.network.await
+import eu.kanade.tachiyomi.source.online.HttpSource
+import eu.kanade.tachiyomi.ui.reader.model.ReaderChapter
+import eu.kanade.tachiyomi.ui.reader.model.ReaderPage
+import eu.kanade.tachiyomi.ui.reader.setting.TextReaderStyle
+import mihon.core.archive.epubReader
+import okhttp3.Request
+import org.json.JSONObject
+import java.io.File
+import java.io.IOException
+import java.util.Locale
+
+/**
+ * Compatibility loader for Kavita document chapters.
+ *
+ * The Kavita extension renders every chapter through /Reader/image. That works
+ * for image/archive content, but EPUB/TXT can fail while Kavita is preparing an
+ * image cache. For document files, download the original chapter and use
+ * Mihon's native document reader instead. Other formats keep the extension's
+ * normal HttpPageLoader behavior.
+ */
+internal class KavitaCompatPageLoader(
+    private val context: Context,
+    private val chapter: ReaderChapter,
+    private val source: HttpSource,
+    private val chapterCache: ChapterCache,
+    private val chapterId: Int,
+    private val textStyle: TextReaderStyle,
+) : PageLoader() {
+
+    override var isLocal: Boolean = false
+    override val usesTextReaderStyle: Boolean
+        get() = delegate?.usesTextReaderStyle == true
+
+    private var delegate: PageLoader? = null
+
+    override suspend fun getPages(): List<ReaderPage> {
+        check(!isRecycled)
+
+        val format = detectDocumentFormat()
+        val loader = when (format) {
+            "epub", "txt" -> createDocumentLoader(format)
+            else -> HttpPageLoader(chapter, source, chapterCache)
+        }
+
+        delegate = loader
+        isLocal = loader.isLocal
+        return loader.getPages()
+    }
+
+    override suspend fun loadPage(page: ReaderPage) {
+        delegate?.loadPage(page)
+    }
+
+    override fun retryPage(page: ReaderPage) {
+        delegate?.retryPage(page)
+    }
+
+    override fun recycle() {
+        delegate?.recycle()
+        delegate = null
+        super.recycle()
+    }
+
+    private suspend fun detectDocumentFormat(): String? {
+        val apiBase = source.baseUrl.trimEnd('/') + "/api"
+        val request = Request.Builder()
+            .url("$apiBase/Chapter?chapterId=$chapterId")
+            .headers(source.headers)
+            .get()
+            .build()
+
+        source.client.newCall(request).await().use { response ->
+            if (!response.isSuccessful) {
+                // Preserve the extension's normal behavior when chapter metadata
+                // cannot be queried. It may still be readable as image content.
+                return null
+            }
+
+            val body = response.body.string()
+            if (body.isBlank()) return null
+
+            val chapterJson = JSONObject(body)
+            val files = chapterJson.optJSONArray("files") ?: return null
+            for (i in 0 until files.length()) {
+                val file = files.optJSONObject(i) ?: continue
+                val extension = normalizeExtension(
+                    file.optString("extension").ifBlank { file.optString("filePath") },
+                )
+                if (extension == "epub" || extension == "txt") {
+                    return extension
+                }
+
+                // Current Kavita format enum: EPUB == 3. TXT has no dedicated
+                // enum value in upstream Kavita, so it is detected by extension.
+                if (file.optInt("format", -1) == 3) {
+                    return "epub"
+                }
+            }
+        }
+        return null
+    }
+
+    private fun normalizeExtension(value: String): String =
+        value.substringAfterLast('.', value)
+            .trim()
+            .trimStart('.')
+            .lowercase(Locale.ROOT)
+
+    private suspend fun createDocumentLoader(format: String): PageLoader {
+        val file = getOrDownloadDocument(format)
+        val uniFile = UniFile.fromFile(file)
+            ?: throw IOException("Unable to open cached Kavita ${format.uppercase()} file")
+
+        return when (format) {
+            "epub" -> EpubPageLoader(uniFile.epubReader(context), textStyle, context.cacheDir)
+            "txt" -> TextPageLoader(uniFile, textStyle, context.cacheDir)
+            else -> error("Unsupported Kavita document format: $format")
+        }
+    }
+
+    private suspend fun getOrDownloadDocument(format: String): File {
+        val cacheDir = File(context.cacheDir, "kavita_reader").apply { mkdirs() }
+        val target = File(cacheDir, "${source.id}-$chapterId.$format")
+        if (target.isFile && target.length() > 0L) return target
+
+        val temp = File(cacheDir, "${target.name}.part")
+        if (temp.exists()) temp.delete()
+
+        val apiBase = source.baseUrl.trimEnd('/') + "/api"
+        val request = Request.Builder()
+            .url("$apiBase/Download/chapter?chapterId=$chapterId")
+            .headers(source.headers)
+            .get()
+            .build()
+
+        source.client.newCall(request).await().use { response ->
+            if (!response.isSuccessful) {
+                val message = when (response.code) {
+                    403 -> "Kavita account does not have Download permission"
+                    404 -> "Kavita original file is missing or no longer available"
+                    500 -> "Kavita could not access the original $format file"
+                    else -> "Kavita document download failed: HTTP ${response.code}"
+                }
+                throw IOException(message)
+            }
+
+            temp.outputStream().use { output ->
+                response.body.byteStream().use { input -> input.copyTo(output) }
+            }
+        }
+
+        if (temp.length() <= 0L) {
+            temp.delete()
+            throw IOException("Kavita returned an empty ${format.uppercase()} file")
+        }
+
+        if (!temp.renameTo(target)) {
+            temp.copyTo(target, overwrite = true)
+            temp.delete()
+        }
+        return target
+    }
+}

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

@@ -1,11 +1,11 @@
 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
-import java.nio.charset.CharacterCodingException
+import java.io.File
+import java.io.InputStreamReader
+import java.io.Reader
 import java.nio.charset.Charset
 import java.nio.charset.CodingErrorAction
 import java.nio.charset.StandardCharsets
@@ -13,39 +13,94 @@ import java.nio.charset.StandardCharsets
 internal class TextPageLoader(
     private val file: UniFile,
     private val style: TextReaderStyle,
+    private val cacheDir: File,
 ) : PageLoader() {
 
     override var isLocal: Boolean = true
     override val usesTextReaderStyle: Boolean = true
 
+    private var pageStore: TextPageStore? = null
+
     override suspend fun getPages(): List<ReaderPage> {
-        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
-            }
-        }
-    }
-
-    private fun decodeText(bytes: ByteArray): String {
-        if (bytes.size >= 3 &&
-            bytes[0] == 0xEF.toByte() &&
-            bytes[1] == 0xBB.toByte() &&
-            bytes[2] == 0xBF.toByte()
-        ) {
-            return String(bytes, 3, bytes.size - 3, StandardCharsets.UTF_8)
-        }
+        pageStore?.close()
+        pageStore = null
 
+        val store = TextPageStore(cacheDir)
         return try {
-            StandardCharsets.UTF_8.newDecoder()
+            val pages = mutableListOf<ReaderPage>()
+            openDecodedReader().use { reader ->
+                TextPageRenderer.paginate(reader, style) { pageText ->
+                    val ref = store.append(pageText)
+                    pages += TextReaderPage(
+                        index = pages.size,
+                        pageTextProvider = { store.read(ref) },
+                        initialStyle = style,
+                    )
+                }
+            }
+            store.finishWriting()
+            pageStore = store
+            pages
+        } catch (e: Throwable) {
+            store.close()
+            throw e
+        }
+    }
+
+    override fun recycle() {
+        pageStore?.close()
+        pageStore = null
+        super.recycle()
+    }
+
+    private fun openDecodedReader(): Reader {
+        val charset = detectCharset()
+        return InputStreamReader(file.openInputStream().buffered(), charset)
+    }
+
+    private fun detectCharset(): Charset {
+        val prefix = ByteArray(3)
+        val prefixSize = file.openInputStream().buffered().use { input ->
+            input.read(prefix)
+        }
+
+        if (
+            prefixSize >= 3 &&
+            prefix[0] == 0xEF.toByte() &&
+            prefix[1] == 0xBB.toByte() &&
+            prefix[2] == 0xBF.toByte()
+        ) {
+            return StandardCharsets.UTF_8
+        }
+        if (prefixSize >= 2 && prefix[0] == 0xFF.toByte() && prefix[1] == 0xFE.toByte()) {
+            return StandardCharsets.UTF_16LE
+        }
+        if (prefixSize >= 2 && prefix[0] == 0xFE.toByte() && prefix[1] == 0xFF.toByte()) {
+            return StandardCharsets.UTF_16BE
+        }
+
+        return if (isValidUtf8()) {
+            StandardCharsets.UTF_8
+        } else {
+            Charset.forName("MS949")
+        }
+    }
+
+    private fun isValidUtf8(): Boolean {
+        val decoder = StandardCharsets.UTF_8.newDecoder()
             .onMalformedInput(CodingErrorAction.REPORT)
             .onUnmappableCharacter(CodingErrorAction.REPORT)
-                .decode(ByteBuffer.wrap(bytes))
-                .toString()
-        } catch (_: CharacterCodingException) {
-            String(bytes, Charset.forName("MS949"))
+
+        return try {
+            InputStreamReader(file.openInputStream().buffered(), decoder).use { reader ->
+                val buffer = CharArray(8 * 1024)
+                while (reader.read(buffer) >= 0) {
+                    // Validation only. Decoded characters are intentionally discarded.
+                }
+            }
+            true
+        } catch (_: Exception) {
+            false
         }
     }
 }

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

@@ -15,47 +15,122 @@ import eu.kanade.tachiyomi.ui.reader.setting.TextReaderStyle
 import java.io.ByteArrayInputStream
 import java.io.ByteArrayOutputStream
 import java.io.InputStream
+import java.io.Reader
+import kotlin.math.roundToInt
 
 internal object TextPageRenderer {
-    private const val PAGE_WIDTH = 1440
-    private const val PAGE_HEIGHT = 2160
-    private const val MARGIN = 96
-    private const val CONTENT_WIDTH = PAGE_WIDTH - (MARGIN * 2)
-    private const val CONTENT_HEIGHT = PAGE_HEIGHT - (MARGIN * 2)
+    private const val MARGIN_DP = 32f
+    private const val STREAM_BUFFER_CHARS = 64 * 1024
+    private const val STREAM_READ_CHARS = 8 * 1024
 
     fun paginate(text: String, style: TextReaderStyle): List<String> {
         if (text.isBlank()) return emptyList()
 
-        val layout = createLayout(text, style)
-        if (layout.lineCount == 0) return listOf(text)
+        return calculatePageSlices(text, style)
+            .mapNotNull { slice ->
+                text.substring(slice.start, slice.endExclusive)
+                    .trim()
+                    .takeIf { it.isNotEmpty() }
+            }
+            .ifEmpty { listOf(text) }
+    }
 
-        val pages = mutableListOf<String>()
+    /**
+     * Incrementally paginates a text stream while keeping only a bounded text
+     * window in memory. The final incomplete page is retained between windows
+     * so normal page filling is preserved across chunk boundaries.
+     */
+    fun paginate(
+        reader: Reader,
+        style: TextReaderStyle,
+        onPage: (String) -> Unit,
+    ) {
+        val working = StringBuilder(STREAM_BUFFER_CHARS + STREAM_READ_CHARS)
+        val chars = CharArray(STREAM_READ_CHARS)
+        var firstChunk = true
+
+        while (true) {
+            val read = reader.read(chars)
+            if (read < 0) break
+            if (read == 0) continue
+
+            var offset = 0
+            if (firstChunk) {
+                firstChunk = false
+                if (chars[0] == '\uFEFF') {
+                    offset = 1
+                }
+            }
+            if (offset < read) {
+                working.append(chars, offset, read - offset)
+            }
+
+            if (working.length >= STREAM_BUFFER_CHARS) {
+                emitCompletePages(working, style, onPage)
+            }
+        }
+
+        if (working.isNotEmpty()) {
+            paginate(working.toString(), style).forEach(onPage)
+        }
+    }
+
+    private fun emitCompletePages(
+        working: StringBuilder,
+        style: TextReaderStyle,
+        onPage: (String) -> Unit,
+    ) {
+        val text = working.toString()
+        val slices = calculatePageSlices(text, style)
+        if (slices.size <= 1) return
+
+        for (index in 0 until slices.lastIndex) {
+            val slice = slices[index]
+            text.substring(slice.start, slice.endExclusive)
+                .trim()
+                .takeIf { it.isNotEmpty() }
+                ?.let(onPage)
+        }
+
+        working.delete(0, slices.last().start)
+    }
+
+    private fun calculatePageSlices(text: String, style: TextReaderStyle): List<PageSlice> {
+        if (text.isEmpty()) return emptyList()
+
+        val metrics = resolveLayoutMetrics(style)
+        val layout = createLayout(text, style, metrics.contentWidth)
+        if (layout.lineCount == 0) return listOf(PageSlice(0, text.length))
+
+        val pages = mutableListOf<PageSlice>()
         var startLine = 0
         while (startLine < layout.lineCount) {
             val startTop = layout.getLineTop(startLine)
             var endLine = startLine
             while (
                 endLine + 1 < layout.lineCount &&
-                layout.getLineBottom(endLine + 1) - startTop <= CONTENT_HEIGHT
+                layout.getLineBottom(endLine + 1) - startTop <= metrics.contentHeight
             ) {
                 endLine++
             }
 
             val start = layout.getLineStart(startLine)
             val end = layout.getLineEnd(endLine).coerceAtLeast(start + 1).coerceAtMost(text.length)
-            text.substring(start, end).trim().takeIf { it.isNotEmpty() }?.let(pages::add)
+            pages += PageSlice(start, end)
             startLine = endLine + 1
         }
-        return pages.ifEmpty { listOf(text) }
+        return pages.ifEmpty { listOf(PageSlice(0, text.length)) }
     }
 
     fun render(text: String, style: TextReaderStyle): InputStream {
-        val bitmap = Bitmap.createBitmap(PAGE_WIDTH, PAGE_HEIGHT, Bitmap.Config.ARGB_8888)
+        val metrics = resolveLayoutMetrics(style)
+        val bitmap = Bitmap.createBitmap(metrics.pageWidth, metrics.pageHeight, Bitmap.Config.ARGB_8888)
         val canvas = Canvas(bitmap)
-        canvas.drawColor(Color.WHITE)
+        val (backgroundColor, _) = resolveColors(style)
+        canvas.drawColor(backgroundColor)
         canvas.save()
-        canvas.translate(MARGIN.toFloat(), MARGIN.toFloat())
-        createLayout(text, style).draw(canvas)
+        canvas.translate(metrics.horizontalMargin.toFloat(), metrics.verticalMargin.toFloat())
+        createLayout(text, style, metrics.contentWidth).draw(canvas)
         canvas.restore()
 
         val output = ByteArrayOutputStream()
@@ -64,24 +139,62 @@ internal object TextPageRenderer {
         return ByteArrayInputStream(output.toByteArray())
     }
 
-    private fun createLayout(text: String, style: TextReaderStyle): StaticLayout {
+    private fun createLayout(
+        text: String,
+        style: TextReaderStyle,
+        contentWidth: Int,
+    ): StaticLayout {
+        val (_, textColor) = resolveColors(style)
         val paint = TextPaint().apply {
             isAntiAlias = true
-            color = Color.BLACK
-            textSize = style.fontSize.toFloat()
+            color = textColor
+            textSize = style.fontSizePx.coerceAtLeast(1f)
             typeface = style.fontFamily.androidFamilyName
                 ?.let { Typeface.create(it, Typeface.NORMAL) }
                 ?: Typeface.DEFAULT
         }
-        val styledText = addParagraphSpacing(text, style.paragraphSpacing)
+        val styledText = addParagraphSpacing(text, style.paragraphSpacingPx)
         return StaticLayout.Builder
-            .obtain(styledText, 0, styledText.length, paint, CONTENT_WIDTH)
+            .obtain(styledText, 0, styledText.length, paint, contentWidth)
             .setAlignment(Layout.Alignment.ALIGN_NORMAL)
             .setIncludePad(true)
             .setLineSpacing(0f, style.lineSpacingPercent / 100f)
             .build()
     }
 
+    private fun resolveLayoutMetrics(style: TextReaderStyle): LayoutMetrics {
+        val pageWidth = style.pageWidthPx.coerceAtLeast(1)
+        val pageHeight = style.pageHeightPx.coerceAtLeast(1)
+        val requestedMargin = (MARGIN_DP * style.density).roundToInt().coerceAtLeast(1)
+        val horizontalMargin = requestedMargin.coerceAtMost(((pageWidth - 1) / 2).coerceAtLeast(0))
+        val verticalMargin = requestedMargin.coerceAtMost(((pageHeight - 1) / 2).coerceAtLeast(0))
+
+        return LayoutMetrics(
+            pageWidth = pageWidth,
+            pageHeight = pageHeight,
+            horizontalMargin = horizontalMargin,
+            verticalMargin = verticalMargin,
+            contentWidth = (pageWidth - horizontalMargin * 2).coerceAtLeast(1),
+            contentHeight = (pageHeight - verticalMargin * 2).coerceAtLeast(1),
+        )
+    }
+
+    private fun resolveColors(style: TextReaderStyle): Pair<Int, Int> {
+        val useDark = when (style.readerTheme) {
+            0 -> false
+            1 -> true
+            2 -> true
+            3 -> style.automaticDark
+            else -> style.automaticDark
+        }
+        val background = when (style.readerTheme) {
+            2 -> Color.rgb(48, 48, 48)
+            else -> if (useDark) Color.BLACK else Color.WHITE
+        }
+        val foreground = if (useDark) Color.WHITE else Color.BLACK
+        return background to foreground
+    }
+
     private fun addParagraphSpacing(text: String, spacing: Int): CharSequence {
         if (spacing <= 0 || '\n' !in text) return text
         val spannable = SpannableString(text)
@@ -111,4 +224,18 @@ internal object TextPageRenderer {
             fm.bottom += spacing
         }
     }
+
+    private data class LayoutMetrics(
+        val pageWidth: Int,
+        val pageHeight: Int,
+        val horizontalMargin: Int,
+        val verticalMargin: Int,
+        val contentWidth: Int,
+        val contentHeight: Int,
+    )
+
+    private data class PageSlice(
+        val start: Int,
+        val endExclusive: Int,
+    )
 }

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

@@ -0,0 +1,69 @@
+package eu.kanade.tachiyomi.ui.reader.loader
+
+import java.io.Closeable
+import java.io.File
+import java.io.RandomAccessFile
+import java.nio.charset.StandardCharsets
+
+/**
+ * Disk-backed storage for text reader pages.
+ *
+ * Keeping page strings here avoids retaining an entire large TXT/EPUB in the
+ * Java heap. Individual pages are loaded only when the viewer renders them.
+ */
+internal class TextPageStore(cacheRoot: File) : Closeable {
+
+    private val cacheDir = File(cacheRoot, "text_reader_pages").apply {
+        mkdirs()
+        pruneStaleFiles()
+    }
+    private val file = File.createTempFile("pages-", ".utf8", cacheDir)
+    private var writer: RandomAccessFile? = RandomAccessFile(file, "rw")
+
+    @Synchronized
+    fun append(text: String): PageRef {
+        val output = checkNotNull(writer) { "Text page store is already finalized" }
+        val bytes = text.toByteArray(StandardCharsets.UTF_8)
+        val offset = output.filePointer
+        output.write(bytes)
+        return PageRef(offset, bytes.size)
+    }
+
+    @Synchronized
+    fun finishWriting() {
+        writer?.fd?.sync()
+        writer?.close()
+        writer = null
+    }
+
+    fun read(ref: PageRef): String {
+        val bytes = ByteArray(ref.byteLength)
+        RandomAccessFile(file, "r").use { input ->
+            input.seek(ref.offset)
+            input.readFully(bytes)
+        }
+        return String(bytes, StandardCharsets.UTF_8)
+    }
+
+    override fun close() {
+        writer?.close()
+        writer = null
+        file.delete()
+    }
+
+    internal data class PageRef(
+        val offset: Long,
+        val byteLength: Int,
+    )
+
+    private fun File.pruneStaleFiles() {
+        val cutoff = System.currentTimeMillis() - STALE_FILE_AGE_MS
+        listFiles()
+            ?.filter { it.isFile && it.lastModified() < cutoff }
+            ?.forEach { it.delete() }
+    }
+
+    private companion object {
+        const val STALE_FILE_AGE_MS = 24L * 60L * 60L * 1000L
+    }
+}

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

@@ -0,0 +1,34 @@
+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 visual style can be refreshed cheaply while layout-affecting
+ * changes trigger a debounced chapter repagination to rebuild page boundaries.
+ */
+internal class TextReaderPage(
+    index: Int,
+    private val pageTextProvider: () -> String,
+    initialStyle: TextReaderStyle,
+) : ReaderPage(index) {
+
+    @Volatile
+    private var style: TextReaderStyle = initialStyle
+
+    init {
+        stream = { TextPageRenderer.render(pageTextProvider(), style) }
+        status = Page.State.Ready
+    }
+
+    constructor(
+        index: Int,
+        pageText: String,
+        initialStyle: TextReaderStyle,
+    ) : this(index, { pageText }, initialStyle)
+
+    fun updateStyle(newStyle: TextReaderStyle) {
+        style = newStyle
+    }
+}

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

@@ -1,6 +1,9 @@
 package eu.kanade.tachiyomi.ui.reader.setting
 
+import android.content.Context
+import android.content.res.Configuration
 import android.os.Build
+import android.util.TypedValue
 import androidx.compose.ui.graphics.BlendMode
 import dev.icerock.moko.resources.StringResource
 import dev.zacsweers.metro.AppScope
@@ -11,6 +14,7 @@ import tachiyomi.core.common.preference.PreferenceStore
 import tachiyomi.core.common.preference.getEnum
 import tachiyomi.core.common.preference.getEnumSet
 import tachiyomi.i18n.MR
+import kotlin.math.roundToInt
 
 @Inject
 @SingleIn(AppScope::class)
@@ -110,23 +114,68 @@ class ReaderPreferences(
 
     // region Text reader
 
-    val textFontSize: Preference<Int> = preferenceStore.getInt("reader_text_font_size", 44)
+    val textFontSize: Preference<Int> = preferenceStore.getInt("reader_text_font_size", 16)
 
     val textLineSpacing: Preference<Int> = preferenceStore.getInt("reader_text_line_spacing", 115)
 
-    val textParagraphSpacing: Preference<Int> = preferenceStore.getInt("reader_text_paragraph_spacing", 12)
+    val textParagraphSpacing: Preference<Int> = preferenceStore.getInt("reader_text_paragraph_spacing", 4)
 
     val textFontFamily: Preference<TextFontFamily> = preferenceStore.getEnum(
         "reader_text_font_family",
         TextFontFamily.SYSTEM,
     )
 
-    fun textReaderStyle() = TextReaderStyle(
+    private val textUnitsMigrated = preferenceStore.getBoolean("reader_text_units_v2_migrated", false)
+
+    init {
+        if (!textUnitsMigrated.get()) {
+            val legacyFontSize = textFontSize.get()
+            if (legacyFontSize > 30) {
+                textFontSize.set((legacyFontSize / 3f).roundToInt().coerceIn(10, 30))
+                textParagraphSpacing.set((textParagraphSpacing.get() / 3f).roundToInt().coerceIn(0, 16))
+            }
+            textUnitsMigrated.set(true)
+        }
+    }
+
+    fun textReaderStyle(context: Context): TextReaderStyle {
+        val displayMetrics = context.resources.displayMetrics
+        val rawWidth = displayMetrics.widthPixels.coerceAtLeast(1)
+        val rawHeight = displayMetrics.heightPixels.coerceAtLeast(1)
+
+        // Keep the same physical page proportions as the device while capping the
+        // raster size so high-resolution phones do not create oversized bitmaps.
+        val renderScale = minOf(
+            1f,
+            TEXT_READER_MAX_RENDER_WIDTH / rawWidth.toFloat(),
+            TEXT_READER_MAX_RENDER_HEIGHT / rawHeight.toFloat(),
+        )
+
+        return TextReaderStyle(
             fontSize = textFontSize.get(),
             lineSpacingPercent = textLineSpacing.get(),
             paragraphSpacing = textParagraphSpacing.get(),
             fontFamily = textFontFamily.get(),
+            readerTheme = readerTheme.get(),
+            automaticDark = (context.resources.configuration.uiMode and Configuration.UI_MODE_NIGHT_MASK) ==
+                Configuration.UI_MODE_NIGHT_YES,
+            pageWidthPx = (rawWidth * renderScale).roundToInt().coerceAtLeast(1),
+            pageHeightPx = (rawHeight * renderScale).roundToInt().coerceAtLeast(1),
+            density = displayMetrics.density * renderScale,
+            fontSizePx = TypedValue.applyDimension(
+                TypedValue.COMPLEX_UNIT_SP,
+                textFontSize.get().toFloat(),
+                displayMetrics,
+            ) * renderScale,
+            paragraphSpacingPx = (
+                TypedValue.applyDimension(
+                    TypedValue.COMPLEX_UNIT_DIP,
+                    textParagraphSpacing.get().toFloat(),
+                    displayMetrics,
+                ) * renderScale
+                ).roundToInt(),
         )
+    }
 
     // endregion
 
@@ -317,6 +366,9 @@ class ReaderPreferences(
         const val WEBTOON_PADDING_MIN = 0
         const val WEBTOON_PADDING_MAX = 25
 
+        private const val TEXT_READER_MAX_RENDER_WIDTH = 1440
+        private const val TEXT_READER_MAX_RENDER_HEIGHT = 2400
+
         const val MILLI_CONVERSION = 100
 
         val TapZones = listOf(
@@ -378,4 +430,11 @@ data class TextReaderStyle(
     val lineSpacingPercent: Int,
     val paragraphSpacing: Int,
     val fontFamily: ReaderPreferences.TextFontFamily,
+    val readerTheme: Int,
+    val automaticDark: Boolean,
+    val pageWidthPx: Int,
+    val pageHeightPx: Int,
+    val density: Float,
+    val fontSizePx: Float,
+    val paragraphSpacingPx: Int,
 )

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

@@ -6,14 +6,18 @@ import eu.kanade.tachiyomi.ui.reader.ReaderViewModel
 import kotlinx.coroutines.flow.SharingStarted
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.distinctUntilChanged
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.flow.stateIn
+import kotlinx.coroutines.launch
 
 class ReaderSettingsViewModel(
     readerState: StateFlow<ReaderViewModel.State>,
     val onChangeReadingMode: (ReadingMode) -> Unit,
     val onChangeOrientation: (ReaderOrientation) -> Unit,
-    val onTextSettingsChanged: () -> Unit,
+    private val onTextSettingsPreview: () -> Unit,
+    private val onTextSettingsCommit: () -> Unit,
     val preferences: ReaderPreferences,
 ) : ViewModel() {
 
@@ -26,4 +30,55 @@ class ReaderSettingsViewModel(
         .map { it.manga }
         .distinctUntilChanged()
         .stateIn(viewModelScope, SharingStarted.Lazily, null)
+
+    private var textSettingsReloadJob: Job? = null
+    private var textAppearanceReloadJob: Job? = null
+    private var textSettingsDirty = false
+
+    /**
+     * Layout-affecting text settings are previewed quickly, then the chapter is
+     * repaginated after a short debounce. This keeps the slider responsive while
+     * ensuring the number of characters/lines on a page follows the new style.
+     */
+    fun requestTextSettingsReload() {
+        textSettingsDirty = true
+        textSettingsReloadJob?.cancel()
+        textSettingsReloadJob = viewModelScope.launch {
+            delay(250)
+            onTextSettingsPreview()
+            textSettingsDirty = false
+            onTextSettingsCommit()
+            textSettingsReloadJob = null
+        }
+    }
+
+    /**
+     * Theme-only changes do not affect page boundaries, so avoid an unnecessary
+     * full repagination.
+     */
+    fun requestTextAppearanceReload() {
+        textAppearanceReloadJob?.cancel()
+        textAppearanceReloadJob = viewModelScope.launch {
+            delay(50)
+            onTextSettingsPreview()
+            textAppearanceReloadJob = null
+        }
+    }
+
+    fun flushTextSettingsReload() {
+        val hadPendingAppearanceReload = textAppearanceReloadJob != null
+        textAppearanceReloadJob?.cancel()
+        textAppearanceReloadJob = null
+        if (!textSettingsDirty) {
+            if (hadPendingAppearanceReload) {
+                onTextSettingsPreview()
+            }
+            return
+        }
+        textSettingsReloadJob?.cancel()
+        textSettingsReloadJob = null
+        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>) {
+    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