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Pdf reflow rework (#51)

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* perf(pdf): native Pdfium-based reflow engine with auto-open

Migrate PDF-to-Markdown reflow generation from PDFBox to a custom
native implementation using Pdfium. This transition improves
processing speed by ~10x and significantly reduces memory overhead.

- Native JNI Bridge: Implemented `pdfium_bridge.cpp` using `dlopen`
  to hook into the existing `libpdfium.so` memory space.
- Optimized Extraction: Replaced character-by-character JNI calls
  with bulk array retrieval (`getPageFontSizes`, `getPageFontWeights`),
  drastically reducing JNI boundary overhead.
- Enhanced Accuracy: Improved Markdown formatting logic by using
  native font weight (bold) and relative font size variance (headers).
- Thread Safety: Refactored generator to process pages sequentially
  while synchronized with the global `PdfiumCore.lock` to ensure
  stability across concurrent UI operations.
- Seamless UX: Implemented a reactive auto-open system in the
  PDF viewer that tracks user intent and navigates to the reflow
  view immediately upon background task completion.

* Improved PDF to Markdown conversion and added cache cleanup.

- Implemented automated cleanup of imported file caches when deleting books.
- Enhanced `PdfToMarkdownGenerator` with support for font flags (italics), improved kerning, and smarter paragraph wrapping.
- Updated `NativePdfiumBridge` and C++ JNI code to extract font information flags from PDFium.

* Implemented seamless file switching and enhanced reflow transition logic.

Key changes include:
- Added `switchToFileSeamlessly` to `MainViewModel` to handle state transitions and navigation when switching between PDF and reflowed text views.
- Updated `generateAndImportReflowFile` to support automatic opening of the generated file at a specific page/chapter.
- Integrated `NavigationEvent` and `CompletableDeferred` to manage asynchronous navigation and state updates during file switches.
- Modified `EpubReaderScreen` and `PdfViewerScreen` to pass the current position when toggling between PDF and text modes.
- Updated `AppNavigation` to move navigation logic out of the `NavHost` and added loading overlays to viewers to improve UI feedback during transitions.
This commit is contained in:
Aryan 2026-03-10 10:59:44 +05:30 • committed by GitHub
parent acf282d4c7
commit c61a264a65
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11 changed files with 940 additions and 419 deletions
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35
app/src/main/java/com/aryan/reader/pdf/PdfViewerScreen.kt
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@ -27,11 +27,7 @@ import android.annotation.SuppressLint
import android.app.Activity
import android.content.Context
import android.content.pm.PackageManager
import androidx.compose.foundation.gestures.awaitEachGesture
import androidx.compose.foundation.gestures.awaitFirstDown
import androidx.compose.foundation.gestures.waitForUpOrCancellation
import android.graphics.Bitmap
import kotlin.math.max
import android.graphics.RectF
import android.net.Uri
import android.os.Build
@ -59,8 +55,11 @@ import androidx.compose.foundation.Image
import androidx.compose.foundation.background
import androidx.compose.foundation.border
import androidx.compose.foundation.clickable
import androidx.compose.foundation.gestures.awaitEachGesture
import androidx.compose.foundation.gestures.awaitFirstDown
import androidx.compose.foundation.gestures.detectDragGestures
import androidx.compose.foundation.gestures.detectDragGesturesAfterLongPress
import androidx.compose.foundation.gestures.waitForUpOrCancellation
import androidx.compose.foundation.interaction.MutableInteractionSource
import androidx.compose.foundation.layout.Arrangement
import androidx.compose.foundation.layout.Box
@ -137,10 +136,8 @@ import androidx.compose.material3.OutlinedTextField
import androidx.compose.material3.RadioButton
import androidx.compose.material3.Scaffold
import androidx.compose.material3.Slider
import androidx.compose.material3.SnackbarDuration
import androidx.compose.material3.SnackbarHost
import androidx.compose.material3.SnackbarHostState
import androidx.compose.material3.SnackbarResult
import androidx.compose.material3.Surface
import androidx.compose.material3.Tab
import androidx.compose.material3.TabRow
@ -286,6 +283,7 @@ import java.io.ByteArrayOutputStream
import java.io.File
import java.net.HttpURLConnection
import java.net.URL
import kotlin.math.max
import kotlin.math.min
import kotlin.math.roundToInt
import kotlin.random.Random
@ -1845,26 +1843,6 @@ fun PdfViewerScreen(
onToggleBookmark(currentPage)
}
LaunchedEffect(reflowInfo) {
if (reflowInfo?.state == WorkInfo.State.SUCCEEDED &&
reflowInfo?.tags?.contains("book_$bookId") == true) {
val result = snackbarHostState.showSnackbar(
message = "Text View generation complete!",
actionLabel = "OPEN",
duration = SnackbarDuration.Long
)
if (result == SnackbarResult.ActionPerformed) {
snackbarHostState.currentSnackbarData?.dismiss()
val item = uiState.recentFiles.find { it.bookId == reflowBookId }
if (item != null) {
viewModel.onRecentFileClicked(item)
}
}
}
}
LaunchedEffect(pdfUri) { debugPdfLinks(context, pdfUri, pdfiumCore, this) }
LaunchedEffect(currentBookId) {
@ -4979,13 +4957,14 @@ fun PdfViewerScreen(
if (hasReflowFile) {
val item = uiState.recentFiles.find { it.bookId == reflowBookId }
if (item != null) {
viewModel.onRecentFileClicked(item)
viewModel.switchToFileSeamlessly(item, currentPage)
}
} else {
viewModel.generateAndImportReflowFile(
pdfBookId = bookId,
pdfUri = pdfUri,
originalTitle = originalFileName
originalTitle = originalFileName,
autoOpenPage = currentPage
)
}
},