opt: read uint8list directly from rust codes

flutter/lib/models/model.dart

@@ -417,8 +417,6 @@ class ImageModel with ChangeNotifier {
 
   String id = '';
 
-  int decodeCount = 0;
-
   WeakReference<FFI> parent;
 
   final List<Function(String)> _callbacksOnFirstImage = [];
@@ -439,20 +437,16 @@ class ImageModel with ChangeNotifier {
       }
     }
 
-    if (decodeCount >= 1) {
-      return;
-    }
-
     final pid = parent.target?.id;
-    decodeCount += 1;
     ui.decodeImageFromPixels(
         rgba,
         parent.target?.ffiModel.display.width ?? 0,
         parent.target?.ffiModel.display.height ?? 0,
         isWeb ? ui.PixelFormat.rgba8888 : ui.PixelFormat.bgra8888, (image) {
-      decodeCount -= 1;
       if (parent.target?.id != pid) return;
       try {
+        // Unlock the rgba memory from rust codes.
+        platformFFI.nextRgba(id);
         // my throw exception, because the listener maybe already dispose
         update(image);
       } catch (e) {
@@ -1370,8 +1364,6 @@ class FFI {
     final cb = ffiModel.startEventListener(id);
     () async {
       // Preserved for the rgba data.
-      Pointer<Uint8>? buffer;
-      int? bufferSize;
       await for (final message in stream) {
         if (message is EventToUI_Event) {
           try {
@@ -1383,29 +1375,15 @@ class FFI {
         } else if (message is EventToUI_Rgba) {
           // Fetch the image buffer from rust codes.
           final sz = platformFFI.getRgbaSize(id);
-          if (sz == null) {
+          if (sz == null || sz == 0) {
             return;
           }
-          // The buffer does not exists or the bufferSize is not
-          // equal to the required size.
-          if (buffer == null || bufferSize != sz) {
-            // reallocate buffer
-            if (buffer != null) {
-              malloc.free(buffer);
-            }
-            buffer = malloc.allocate(sz);
-            bufferSize = sz;
-          }
-          final rgba = platformFFI.getRgba(id, buffer, bufferSize!);
+          final rgba = platformFFI.getRgba(id, sz);
           if (rgba != null) {
             imageModel.onRgba(rgba);
           }
         }
       }
-      // Free the buffer allocated on the heap.
-      if (buffer != null) {
-        malloc.free(buffer);
-      }
     }();
     // every instance will bind a stream
     this.id = id;

flutter/lib/models/native_model.dart

@@ -9,6 +9,7 @@ import 'package:ffi/ffi.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_hbb/consts.dart';
+import 'package:get/get.dart';
 import 'package:package_info_plus/package_info_plus.dart';
 import 'package:path_provider/path_provider.dart';
 import 'package:win32/win32.dart' as win32;
@@ -23,10 +24,11 @@ class RgbaFrame extends Struct {
 }
 
 typedef F2 = Pointer<Utf8> Function(Pointer<Utf8>, Pointer<Utf8>);
-typedef F3 = Void Function(Pointer<Utf8>, Pointer<Uint8>);
-typedef F3Dart = void Function(Pointer<Utf8>, Pointer<Uint8>);
+typedef F3 = Pointer<Uint8> Function(Pointer<Utf8>);
 typedef F4 = Uint64 Function(Pointer<Utf8>);
 typedef F4Dart = int Function(Pointer<Utf8>);
+typedef F5 = Void Function(Pointer<Utf8>);
+typedef F5Dart = void Function(Pointer<Utf8>);
 typedef HandleEvent = Future<void> Function(Map<String, dynamic> evt);
 
 /// FFI wrapper around the native Rust core.
@@ -47,8 +49,9 @@ class PlatformFFI {
   final _toAndroidChannel = const MethodChannel('mChannel');
 
   RustdeskImpl get ffiBind => _ffiBind;
-  F3Dart? _session_get_rgba;
+  F3? _session_get_rgba;
   F4Dart? _session_get_rgba_size;
+  F5Dart? _session_next_rgba;
 
   static get localeName => Platform.localeName;
 
@@ -97,13 +100,19 @@ class PlatformFFI {
     return res;
   }
 
-  Uint8List? getRgba(String id, Pointer<Uint8> buffer, int bufSize) {
+  Uint8List? getRgba(String id, int bufSize) {
     if (_session_get_rgba == null) return null;
     var a = id.toNativeUtf8();
-    _session_get_rgba!(a, buffer);
-    final data = buffer.asTypedList(bufSize);
-    malloc.free(a);
-    return data;
+    try {
+      final buffer = _session_get_rgba!(a);
+      if (buffer == nullptr) {
+        return null;
+      }
+      final data = buffer.asTypedList(bufSize);
+      return data;
+    } finally {
+      malloc.free(a);
+    }
   }
 
   int? getRgbaSize(String id) {
@@ -114,6 +123,13 @@ class PlatformFFI {
     return bufferSize;
   }
 
+  void nextRgba(String id) {
+    if (_session_next_rgba == null) return;
+    final a = id.toNativeUtf8();
+    _session_next_rgba!(a);
+    malloc.free(a);
+  }
+
   /// Init the FFI class, loads the native Rust core library.
   Future<void> init(String appType) async {
     _appType = appType;
@@ -129,8 +145,11 @@ class PlatformFFI {
     debugPrint('initializing FFI $_appType');
     try {
       _translate = dylib.lookupFunction<F2, F2>('translate');
-      _session_get_rgba = dylib.lookupFunction<F3, F3Dart>("session_get_rgba");
-      _session_get_rgba_size = dylib.lookupFunction<F4, F4Dart>("session_get_rgba_size");
+      _session_get_rgba = dylib.lookupFunction<F3, F3>("session_get_rgba");
+      _session_get_rgba_size =
+          dylib.lookupFunction<F4, F4Dart>("session_get_rgba_size");
+      _session_next_rgba =
+          dylib.lookupFunction<F5, F5Dart>("session_next_rgba");
       try {
         // SYSTEM user failed
         _dir = (await getApplicationDocumentsDirectory()).path;