* 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.

2026-03-10 10:59:44 +05:30

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Episteme Reader

A native Android document reader application built with Kotlin and Jetpack Compose.

Overview

Episteme Reader is an offline-first application designed for reading various document formats. It leverages native Android technologies and C++ libraries to provide a performant reading experience with customization capabilities.

Note: This is the Open Source (OSS) edition of Episteme Reader. The version available on the Google Play Store is built from this core but includes additional proprietary features.

Features

Supported Formats

Documents: PDF
E-books: EPUB, MOBI, AZW3
Text: MD, TXT, HTML

PDF Features

Viewing Modes: Vertical Scroll and Paginated view.
Ink Annotations: Draw directly on pages using Pen, Highlighter, and Eraser tools.
Text Annotations: Add text notes anywhere on the page using system or custom fonts.

E-Book Features

Parsing: Native parsing for MOBI/AZW3 via libmobi and EPUB via Jsoup.
Customization: Adjust font size, line spacing, and margins.
Custom Fonts: Support for importing user-provided font files (.ttf, .otf).

General

Text-to-Speech (TTS): Read documents aloud using the system TTS engine.
File Management: Built-in library organization.

Architecture

UI: 100% Jetpack Compose (Material3).
Architecture: MVVM with Unidirectional Data Flow.
Database: Room (SQLite) for metadata and annotations.
PDF Engine: pdfium-android (Native PDFium bindings).
EPUB Engine: Utilizes standard WebView for vertical scrolling mode, and a custom rendering engine for paginated mode.
Mobi Engine: Custom JNI bindings to libmobi.

Building from Source

Clone the repository:

git clone https://github.com/Aryan-Raj3112/episteme.git
cd episteme

Build: Open in Android Studio and run the ossDebug variant.
```
./gradlew assembleOssDebug
```

Open Source Libraries

This project is made possible by the Android open-source ecosystem:

Core & UI: AndroidX, Jetpack Compose, Kotlinx Serialization
Document Engines: PdfiumAndroidKt (PDF), libmobi (MOBI/AZW3), Google WOFF2 (Fonts)
Parsers: Jsoup (HTML/EPUB), Flexmark (Markdown)
Media & Image Loading: Coil, Media3 (ExoPlayer)
Utilities: Room (Database), Timber (Logging)

License

This project is licensed under the GNU Affero General Public License v3.0 (AGPL-3.0). See the LICENSE file for details.

Support

If you find Episteme Reader useful and want to support its development, please consider sponsoring. Thank you!

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