Build tools for Flutter GPU shader bundles/libraries.

Features

Use native asset build hooks to import Flutter GPU shader bundle assets.

Getting started

1. This package requires the experimental "native assets" feature to be enabled. Enable it with the following command:

   flutter config --enable-native-assets
   

2. Place some Flutter GPU shaders in your project. For this example, we'll assume the existence of two shaders: shaders/my_cool_shader.vert and shaders/my_cool_shader.frag.
3. Create a shader bundle manifest file in your project. The filename must end with .shaderbundle.json. For this example, we'll assume the following file is saved as my_cool_bundle.shaderbundle.json:

   {
       "CoolVertex": {
           "type": "vertex",
           "file": "shaders/my_cool_shader.vert"
       },
       "CoolFragment": {
           "type": "fragment",
           "file": "shaders/my_cool_shader.frag"
       }
   }
   

4. Next, define a build hook in your project that builds the shader bundle using buildShaderBundleJson. The build hook must be named hook/build.dart in your project; this script will be automatically invoked by Flutter when the "native assets" feature is enabled:

   import 'package:native_assets_cli/native_assets_cli.dart';
   import 'package:flutter_gpu_shaders/build.dart';
   
   void main(List<String> args) async {
     await build(args, (config, output) async {
       await buildShaderBundleJson(
           buildConfig: config,
           buildOutput: output,
           manifestFileName: 'my_cool_bundle.shaderbundle.json');
     });
   }
   

5. In your project's pubspec.yaml, add an asset import rule to package the built shader bundles (this will become unnecessary once "native assets" supports DataAsset in a future release of Flutter):

   flutter:
     assets:
       - build/shaderbundles/*.shaderbundle.json
   

6. You can now import the built shader bundle as a library using gpu.ShaderLibrary.fromAsset in your project. For example:

   import 'package:flutter_gpu/gpu.dart' as gpu;
      
   final String _kBaseShaderBundlePath =
       'packages/my_project/build/shaderbundles/my_cool_bundle.shaderbundle';
      
   gpu.ShaderLibrary? _baseShaderLibrary = null;
   gpu.ShaderLibrary get baseShaderLibrary {
     if (_baseShaderLibrary != null) {
       return _baseShaderLibrary!;
     }
     _baseShaderLibrary = gpu.ShaderLibrary.fromAsset(_kBaseShaderBundlePath);
     if (_baseShaderLibrary != null) {
       return _baseShaderLibrary!;
     }
      
     throw Exception(
         "Failed to load base shader bundle! ($_kBaseShaderBundlePath)");
   }