Flutter - Win32程序的消息是如何传递给dart

发现: \engine-main\third_party\tonic\logging\dart_invoke.h 让c++代码调用dart代码 

tonic库的官方链接地址:

https://pub-web.flutter-io.cn/packages/tonichttps://pub-web.flutter-io.cn/packages/tonic

// \engine-main\shell\platform\windows\flutter_window.cc
// 主要分析 WM_MOUSEMOVE 事件

WNDCLASS FlutterWindow::RegisterWindowClass(std::wstring& title) {
  window_class_name_ = title;

  WNDCLASS window_class{};
  window_class.hCursor = LoadCursor(nullptr, IDC_ARROW);
  window_class.lpszClassName = title.c_str();
  window_class.style = CS_HREDRAW | CS_VREDRAW;
  window_class.cbClsExtra = 0;
  window_class.cbWndExtra = 0;
  window_class.hInstance = GetModuleHandle(nullptr);
  window_class.hIcon = nullptr;
  window_class.hbrBackground = 0;
  window_class.lpszMenuName = nullptr;
  window_class.lpfnWndProc = WndProc;
  RegisterClass(&window_class);
  return window_class;
}

LRESULT CALLBACK FlutterWindow::WndProc(HWND const window,
                                        UINT const message,
                                        WPARAM const wparam,
                                        LPARAM const lparam) noexcept {
  if (message == WM_NCCREATE) {
    auto cs = reinterpret_cast<CREATESTRUCT*>(lparam);
    SetWindowLongPtr(window, GWLP_USERDATA,
                     reinterpret_cast<LONG_PTR>(cs->lpCreateParams));

    auto that = static_cast<FlutterWindow*>(cs->lpCreateParams);
    that->window_handle_ = window;
    that->text_input_manager_->SetWindowHandle(window);
    RegisterTouchWindow(window, 0);
  } else if (FlutterWindow* that = GetThisFromHandle(window)) {
    return that->HandleMessage(message, wparam, lparam);
  }

  return DefWindowProc(window, message, wparam, lparam);
}

LRESULT
FlutterWindow::HandleMessage(UINT const message,
                             WPARAM const wparam,
                             LPARAM const lparam) noexcept {
  LPARAM result_lparam = lparam;
  int xPos = 0, yPos = 0;
  UINT width = 0, height = 0;
  UINT button_pressed = 0;
  FlutterPointerDeviceKind device_kind;

  
  // switch分支中省略了很多代码

  switch (message) {
    case kWmDpiChangedBeforeParent:
      current_dpi_ = GetDpiForHWND(window_handle_);
      OnDpiScale(current_dpi_);
      return 0;
    case WM_SIZE:
      width = LOWORD(lparam);
      height = HIWORD(lparam);

      current_width_ = width;
      current_height_ = height;
      HandleResize(width, height);

      OnWindowStateEvent(width == 0 && height == 0 ? WindowStateEvent::kHide
                                                   : WindowStateEvent::kShow);
      break;
    case WM_PAINT:
      OnPaint();
      break;
    case WM_MOUSEMOVE:
      device_kind = GetFlutterPointerDeviceKind();
      if (device_kind == kFlutterPointerDeviceKindMouse) {
        TrackMouseLeaveEvent(window_handle_);

        xPos = GET_X_LPARAM(lparam);
        yPos = GET_Y_LPARAM(lparam);
        mouse_x_ = static_cast<double>(xPos);
        mouse_y_ = static_cast<double>(yPos);

        int mods = 0;
        if (wparam & MK_CONTROL) {
          mods |= kControl;
        }
        if (wparam & MK_SHIFT) {
          mods |= kShift;
        }
        // ---------->>>>>>>>>> 调用 OnPointerMove
        OnPointerMove(mouse_x_, mouse_y_, device_kind, kDefaultPointerDeviceId,
                      mods);
      }
      break;
    case WM_MOUSELEAVE:
      device_kind = GetFlutterPointerDeviceKind();
      if (device_kind == kFlutterPointerDeviceKindMouse) {
        OnPointerLeave(mouse_x_, mouse_y_, device_kind,
                       kDefaultPointerDeviceId);
      }

      // Once the tracked event is received, the TrackMouseEvent function
      // resets. Set to false to make sure it's called once mouse movement is
      // detected again.
      tracking_mouse_leave_ = false;