Integrate Rust with Flutter using flutter_rust_bridge

Use Case: Implementing a computationally intensive algorithm like cryptography, signal processing, or scientific simulations.

Example: A secure messaging app using end-to-end encryption could offload encryption and decryption to Rust for optimized performance.

Use Case: Manipulating or analyzing multimedia files, such as applying filters or extracting metadata.

Example: A photo editing app could use Rust to apply complex filters or handle encoding/decoding for custom media formats.

Here’s how you can start integrating Rust with Flutter:

1. Install flutter_rust_bridge_codegen: First, you need to install the flutter_rust_bridge_codegen tool using Cargo, Rust's package manager:

2. Add the Required DependenciesAdd the flutter_rust_bridge package as a dependency in your pubspec.yaml file:Next, add the ffi package to the dev_dependencies and configure the plugin settings to enable FFI (Foreign Function Interface) on supported platforms:

The ffi package is essential because it allows Dart to interact with native Rust code. It does this by using dynamic libraries (e.g., .dll for Windows, .so for Linux, and .dylib for macOS). Without ffi, Flutter can’t directly call the native functions from the compiled Rust library. You can manually interface with Rust by writing FFI bindings yourself without using flutter_rust_bridge but using it is more convenient.

3. Create the Configuration FileIn your project root, create a file named flutter_rust_bridge.yaml to specify the Rust code location and where the generated Dart code should go:
4. Set Up the Rust ProjectIn the root folder, initialize a new Rust library project with the following command:This creates a new Rust project inside the rust/ folder, which will contain the Rust code.

1. Structure Your Rust CodeNow, let’s create the necessary Rust code to make it compatible with Flutter. Start by creating an api.rs file in your rust/src directory. The lib.rs file should import api.rs and the code generated by flutter_rust_bridge:

Below is an example of how to structure your Rust code in a way that is compatible with Flutter using the flutter_rust_bridge macro.

Under the hood we are using the pdfium_render rust library.

The pdfium.dll file is required for the library to work on your system. While this file can be installed on the system itself, we can also package it with the application to make things easier. To do this, we need to place the pdfium.dll into the environment-specific build folder during the build process. This is done by modifying the project's CMakeLists.txt file.

CMake is a build tool used to manage the building process of applications, especially for cross-platform development. It helps generate build files specific to the platform you're targeting, like Windows, macOS, or Linux.

To ensure the pdfium.dll file is included in the build, we can add the following lines to the end of the CMakeLists.txt:

• SOURCE_DLL: This defines the path where the pdfium.dll file is located. Here, it points to windows/include/pdfium.dll.
• BUILD_FOLDER: This defines the path where the pdfium.dll will be copied. The destination depends on the environment you're building for.

For example, running:

will place the pdfium.dll file in the build\\windows\\x64\\runner\\Debug folder. The install command handles copying the file to the appropriate location during the build process.

In this example:

• Modules: Rust modules are used to organize different file types (CSV, DOCX, PDF) extraction logic.
• flutter_rust_bridge Macro: The #[flutter_rust_bridge::frb(dart_async)] macro is added to the extract function, making it callable from Dart and handling async tasks.
• Infer File Type: The infer crate is used to determine the file type from the file path and apply the appropriate extraction logic.

6. Run Code GenerationOnce your Rust code is set up, you need to run the code generator to create the Dart bindings. In the root folder of your project, run:This will generate Dart code for you in the specified dart_output directory (lib/rust).

/im

1. Use the Generated Dart CodeAfter running the code generator, you will find the generated Dart code in the lib/rust directory. This code acts as the bridge between Flutter and Rust, allowing you to call Rust functions from your Dart code easily.Example usage of the generated Dart code:

By following these steps, you can harness the power of Rust within your Flutter apps using the flutter_rust_bridge. This setup allows you to offload performance-critical tasks to Rust, ensuring that your Flutter app stays responsive while handling complex operations efficiently.

Integrating Flutter and Rust is a powerful way to combine Flutter's cross-platform strengths with Rust's performance, giving you the best of both worlds.

You can check out the pdf_ocr package in action here, where you can find an example project for testing.