pdfium_dart

Dart FFI bindings for the PDFium library. This package provides low-level access to PDFium's C API from Dart.

This package is part of the pdfrx project.

Overview

This package contains auto-generated FFI bindings for PDFium using ffigen. It is designed to be a minimal, pure Dart package that other packages can depend on to access PDFium functionality.

Key Features:

Pure Dart package with no Flutter dependencies
Auto-generated FFI bindings using ffigen
Provides direct access to PDFium's C API
Downloads and bundles PDFium at build time using Dart native assets
Includes getPdfium() for resolving PDFium across Dart and Flutter runtimes
Supports Windows, Linux, Android, and macOS build hooks

Usage

Basic Usage

This package is primarily intended to be used as a dependency by higher-level packages like pdfium_flutter and pdfrx_engine. Direct usage is possible but not recommended unless you need low-level PDFium access.

import 'package:pdfium_dart/pdfium_dart.dart';
import 'dart:ffi';

// If you already have PDFium loaded
final pdfium = PDFium(DynamicLibrary.open('/path/to/libpdfium.so'));

PDFium Loading

The getPdfium function resolves the PDFium library for the current runtime. You can also pass an explicit module path for custom deployments or tests:

import 'package:pdfium_dart/pdfium_dart.dart';

void main() async {
  // Resolves PDFium for the current Dart or Flutter runtime.
  final pdfium = getPdfium();

  // Or load a specific shared library.
  final customPdfium = getPdfium(modulePath: '/path/to/libpdfium.so');

  // Use PDFium API
  // ...
}

The build hook downloads binaries from bblanchon/pdfium-binaries and exposes them through Dart native assets. At runtime, getPdfium() chooses the appropriate loading strategy:

modulePath is used first when explicitly provided.
Flutter apps on iOS/macOS use the PDFium XCFramework that is already linked into the app by pdfium_flutter.
Native PDFium assets are not built for iOS; Flutter iOS apps should depend on pdfium_flutter so the XCFramework is linked by the Flutter plugin.
Pure Dart commands on macOS, such as dart test, dart run, and dart compile, use the libpdfium.dylib native asset.
Flutter apps on Linux look for libpdfium.so in the shared library directory relative to the resolved executable.
Other supported platforms first try the platform library name, then fall back to the bundled native asset recorded in .dart_tool/native_assets.yaml.

Generating Bindings

Prerequisites

The ffigen process requires LLVM/Clang to be installed for parsing C headers:

macOS: Install via Homebrew
```
brew install llvm
```

Linux: Install via package manager

# Ubuntu/Debian
sudo apt-get install libclang-dev

# Fedora
sudo dnf install clang-devel

Windows: Download and install LLVM from llvm.org

Regenerating Bindings

To regenerate the FFI bindings:

Run tests once to download PDFium headers into test/.tmp:
```
dart test
```
Generate bindings:
```
dart run ffigen
```

The bindings are generated from PDFium headers using the configuration in ffigen.yaml.

Platform Support

Platform	Architecture	Support
Windows	x64, ARM64, x86	✅
Linux	x64, ARM64, ARM, x86	✅
Android	ARM64, ARMv7, x86, x86_64	✅
macOS	x64, ARM64	✅

Note: For Flutter applications, use pdfium_flutter unless you specifically need the lower-level Dart bindings directly. pdfium_flutter includes the Flutter deployment layer for all native platforms except Web.