flutter_opengl_view 0.0.3

OpenGL plugin with native iOS (OBJC) & Android (JAVA) support as well as C++.

flutter_opengl_view

The flutter openGL plugin enables openGL rendering on Android and iOS.

With this plugin, you can use native (Android, iOS) openGL calls as well as
C++ openGL code.

Usage

Add plugin in pubspec.yaml:

# pubspec.yaml

dependencies:
  flutter:
    sdk: flutter

  flutter_opengl_view: ^0.0.1
 

Add plugin in Flutter code:

import 'package:flutter_opengl_view/flutter_opengl_view.dart';

Widget build(BuildContext context) {
  
  /* use a ffi call to your c++ code, to get a proper pointer.
   * myCppPointer = 0 will use ios/android openGL rendering, but not c++. 
   */
  int myCppPointer = 0; 
  
  FlutterOpenglView openGlView = const FlutterOpenglView(
      cPlusPlusPointer: myCppPointer,
      useTextureView: true
  );

  return MaterialApp(
    home: Scaffold(
      body: SizedBox(
        width: 300.0,
        height: 300.0,
        child: openGlView // Add the openGL plugin in arbitrary parts of the widget tree.
      ),
    ),
  );
}

• If your render with native iOS/Android code (objc/Java), cPlusPlusPointer can be set to zero.
• useTextureView = true (default) uses a TextureView on Android, while useTextureView = false uses an GLSurfaceView.
  • GLSurfaceViews can not be rotated, for example but lead to higher performance. In addition, they do not allow to properly overlap with other views or widgets.

Own C++ class

To use your own c++ opengl code, you must extend the class FlutterOpenGL:

# header for MyFlutterOpenGL class:

class MyFlutterOpenGL : public FlutterOpenGL {

public:

    MyFlutterOpenGL();

    virtual ~FlutterGL();

    void init(int width, int height);

    void stopDrawFrame();

    void onDrawFrame();

    bool isReady();
};

onDrawFrame() is continually called by the openGL thread.
init() is called by the openGL thread as well and can be used to initialize resources and configure openGL.

C++ / Dart Example Interface

Interfacing c++ from dart can look as follows:

C++ Part:

On the c++ side, you have to obtain a pointer to an FlutterOpenGL instance:

#include <cstdint>

#if __cplusplus

#if defined(_WIN32)
#define DART_EXPORT extern "C" __declspec(dllexport)
#else
#define DART_EXPORT                                                            \
  extern "C" __attribute__((visibility("default"))) __attribute((used))
#endif

// Returns a pointer of an FlutterOpenGL object, casted to int64_t.
DART_EXPORT int64_t getFlutterOpenGL() {
  MyFlutterOpenGL* flutterOpenGl = new MyFlutterOpenGL();
  
  int64_t flutterOpenGlReference = reinterpret_cast<int64_t>(flutterOpenGl);
  return flutterOpenGlReference;
}

#endif  // __cplusplus

Dart Part:

Dart retrieves the c++ pointer (previously casted to Int64) and hands it over to the constructor.

final DynamicLibrary myFfiLibrary = Platform.isAndroid
    ? DynamicLibrary.open("myFfiLibrary.so")    // same name as in CMake file
    : DynamicLibrary.process();

/// Returns a pointer to an FlutterOpenGL object and can be handed over to the dart constructor of
/// FlutterOpenglView().
final int Function() getFlutterOpenGL = myFfiLibrary
    .lookup<NativeFunction<Int64 Function()>>("getFlutterOpenGL")
    .asFunction();

More Information:

Use C++ code in Android

In your own plugin or application, add the c++ source code destination to your build.gradle.
Check Flutter c-interop page for more details.

use C++ for IOS in XCode

• XCode: Select "Compile Source As" variable in compiler settings and set its value to "Objective-C++"
• change Obj-C file to .mm
• add c++ sources within XCode: Runner -> Target -> Build Phases

CheckFlutter c-interop page for more details.

Usage from another plugin:

• create flutter plugin that will contain your C++ openGL code flutter create -a java -i objc --template=plugin

• add flutter_opengl_view to your created plugin (in pubspec.yaml, dependencies section)

• add Key to

Contact

for more information, feel free to contact me: dev @ jscheer.de