Reduce reader memory pressure

Author: FredApps

app/src/main/kotlin/com/fredapp/wbooks/transfer/UploadServer.kt

@@ -14,8 +14,10 @@ import com.fredapp.wbooks.util.uniqueFile
 import fi.iki.elonen.NanoHTTPD
 import kotlinx.coroutines.runBlocking
 import java.io.File
+import java.io.IOException
 import java.net.URLDecoder
 import java.net.URLEncoder
+import java.nio.file.Files
 import java.security.MessageDigest
 
 /**
@@ -1095,7 +1097,7 @@ class UploadServer(
             val safeName = originalName.replace(Regex("[\\\\/:*?\"<>|]"), "_")
             val dest = uniqueFile(targetDir, safeName)
             if (!dest.isInsideBooksDir() || dest.canonicalFile == booksDir.canonicalFile) continue
-            File(tempPath).copyTo(dest, overwrite = false)
+            moveUploadedTemp(File(tempPath), dest)
             appendToOrder(targetDir, dest.name)
             written++
         }
@@ -1505,6 +1507,15 @@ class UploadServer(
         writeOrder(dir, listOf(name) + readOrder(dir).keys.filterNot { it == name })
     }
 
+    private fun moveUploadedTemp(temp: File, dest: File) {
+        try {
+            Files.move(temp.toPath(), dest.toPath())
+        } catch (_: IOException) {
+            temp.copyTo(dest, overwrite = false)
+            temp.delete()
+        }
+    }
+
     private fun currentTopFolderNames(): List<String> =
         booksDir.listFiles { f -> f.isDirectory }
             ?.map { it.name }

app/src/main/kotlin/com/fredapp/wbooks/ui/ReaderViewModel.kt

@@ -151,6 +151,7 @@ class ReaderViewModel(
     private val _document = MutableStateFlow<DocumentState>(DocumentState.Idle)
     val document: StateFlow<DocumentState> = _document.asStateFlow()
     private var loadJob: Job? = null
+    private var cacheStoreJob: Job? = null
 
     /**
      * Identity of the currently-open book, or null when nothing is open.
@@ -599,6 +600,7 @@ class ReaderViewModel(
 
     fun openBook(book: Book) {
         loadJob?.cancel()
+        cacheStoreJob?.cancel()
         // Reset pace baseline so the first reportPosition after the new book
         // loads doesn't compute a cross-book delta.
         lastAdvancePosition = null
@@ -681,13 +683,14 @@ class ReaderViewModel(
                 parseBook(book).also { parsed ->
                     updateLoadingProgress(book, 95, "Preparing reader")
                     Log.i(TAG, "Parsed ${book.id} (${book.format}) in ${System.currentTimeMillis() - startedAt}ms")
-                    appScope.launch(Dispatchers.IO) {
+                    cacheStoreJob = appScope.launch(Dispatchers.IO) {
                         val storeStartedAt = System.currentTimeMillis()
                         runCatching { documentCache.store(key, parsed) }
                             .onSuccess {
                                 Log.i(TAG, "Cached ${book.id} in ${System.currentTimeMillis() - storeStartedAt}ms")
                             }
                             .onFailure {
+                                if (it is kotlinx.coroutines.CancellationException) throw it
                                 Log.w(TAG, "Failed to cache ${book.id}", it)
                             }
                     }
@@ -735,9 +738,17 @@ class ReaderViewModel(
 
     fun closeBook() {
         loadJob?.cancel()
+        cacheStoreJob?.cancel()
         _document.value = DocumentState.Idle
     }
 
+    override fun onCleared() {
+        loadJob?.cancel()
+        cacheStoreJob?.cancel()
+        sessionFlushJob?.cancel()
+        super.onCleared()
+    }
+
     // ---- Settings edits ----
     fun cycleMode() = editSettings { it.copy(mode = it.mode.next()) }
     fun cycleFont() = editSettings { it.copy(font = it.font.next()) }

app/src/main/kotlin/com/fredapp/wbooks/ui/reader/BlockRendering.kt

@@ -16,6 +16,7 @@ import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.graphics.asImageBitmap
 import androidx.compose.ui.layout.ContentScale
 import androidx.compose.ui.platform.LocalConfiguration
+import androidx.compose.ui.platform.LocalDensity
 import androidx.compose.ui.text.AnnotatedString
 import androidx.compose.ui.text.SpanStyle
 import androidx.compose.ui.text.buildAnnotatedString
@@ -110,8 +111,9 @@ private fun ImageBlockView(
     val isRound = config.isScreenRound
     val minAxis = min(config.screenWidthDp, config.screenHeightDp).dp
     val safeSide = if (isRound) (minAxis * (1f / sqrt(2f))) else minAxis
-    val bitmap = remember(block) {
-        runCatching { BitmapFactory.decodeByteArray(block.bytes, 0, block.bytes.size) }.getOrNull()
+    val maxBitmapPx = with(LocalDensity.current) { safeSide.roundToPx() }.coerceAtLeast(1)
+    val bitmap = remember(block, maxBitmapPx) {
+        decodeSampledBitmap(block.bytes, maxBitmapPx)
     }
     Box(
         modifier = Modifier
@@ -142,6 +144,30 @@ private fun ImageBlockView(
     }
 }
 
+/**
+ * Decode at roughly the largest size the watch can display. EPUB cover art can
+ * easily be thousands of pixels wide; decoding those full-size bitmaps for a
+ * 300-450 px display is wasted heap and a classic path to OOM on Wear OS.
+ */
+private fun decodeSampledBitmap(bytes: ByteArray, maxDisplayPx: Int): android.graphics.Bitmap? =
+    runCatching {
+        val bounds = BitmapFactory.Options().apply { inJustDecodeBounds = true }
+        BitmapFactory.decodeByteArray(bytes, 0, bytes.size, bounds)
+        if (bounds.outWidth <= 0 || bounds.outHeight <= 0) return@runCatching null
+
+        var sample = 1
+        val longest = maxOf(bounds.outWidth, bounds.outHeight)
+        while (longest / (sample * 2) >= maxDisplayPx) {
+            sample *= 2
+        }
+
+        val options = BitmapFactory.Options().apply {
+            inSampleSize = sample
+            inPreferredConfig = android.graphics.Bitmap.Config.RGB_565
+        }
+        BitmapFactory.decodeByteArray(bytes, 0, bytes.size, options)
+    }.getOrNull()
+
 private fun List<Run>.toAnnotatedString(): AnnotatedString = buildAnnotatedString {
     for (run in this@toAnnotatedString) {
         val style = SpanStyle(