Avalonia中NativeControlHost嵌入SDL2无法捕获SDL_KEYDOWN/SDL_KEYUP事件

我有一个基于Avalonia开发的应用，希望将一个使用SDL2-CS wrapper开发的C# SDL2应用嵌入其中。我通过以下代码使用NativeControlHost获取句柄：

public class NativeEmbeddingControl : NativeControlHost
{
    public IntPtr Handle { get; private set; }

    protected override IPlatformHandle CreateNativeControlCore(IPlatformHandle parent)
    {
        var handle = base.CreateNativeControlCore(parent);
        Handle = handle.Handle;
        return handle;
    }
}

随后通过该句柄创建SDL2窗口：

IntPtr windowPtr = SDL.SDL_CreateWindowFrom(windowHandle);

SDL2应用的内容可正常显示，但调用SDL_PollEvent时无法获取SDL_KEYDOWN和SDL_KEYUP事件；而SDL2应用独立运行时一切功能正常。请问需要额外执行哪些操作，才能将按键上下事件传递给嵌入式SDL2应用？

要让嵌入式SDL2窗口接收键盘事件，需要手动在Avalonia的NativeEmbeddingControl中处理键盘事件并转发给SDL2窗口，具体操作如下：

• 重写NativeControlHost的键盘事件处理方法
  在你的NativeEmbeddingControl类中，重写OnKeyDown、OnKeyUp等方法，将Avalonia的键盘事件转换为SDL2格式后，通过SDL_PushEvent推送给SDL2窗口。示例代码：

  public class NativeEmbeddingControl : NativeControlHost
  {
      public IntPtr Handle { get; private set; }
      private IntPtr _sdlWindow;
  
      // 保存SDL窗口句柄
      public void SetSdlWindow(IntPtr sdlWindow)
      {
          _sdlWindow = sdlWindow;
      }
  
      protected override IPlatformHandle CreateNativeControlCore(IPlatformHandle parent)
      {
          var handle = base.CreateNativeControlCore(parent);
          Handle = handle.Handle;
          return handle;
      }
  
      protected override void OnKeyDown(KeyEventArgs e)
      {
          base.OnKeyDown(e);
          if (_sdlWindow == IntPtr.Zero) return;
  
          var sdlKey = ConvertAvaloniaKeyToSdl(e.Key);
          if (sdlKey != SDL.SDL_Keycode.SDLK_UNKNOWN)
          {
              var sdlEvent = new SDL.SDL_Event
              {
                  key = new SDL.SDL_KeyboardEvent
                  {
                      type = SDL.SDL_EventType.SDL_KEYDOWN,
                      windowID = SDL.SDL_GetWindowID(_sdlWindow),
                      keysym = new SDL.SDL_Keysym
                      {
                          sym = sdlKey,
                          mod = ConvertAvaloniaModifiersToSdl(e.KeyModifiers)
                      }
                  }
              };
              SDL.SDL_PushEvent(ref sdlEvent);
              e.Handled = true; // 标记事件已处理，避免Avalonia继续拦截
          }
      }
  
      protected override void OnKeyUp(KeyEventArgs e)
      {
          base.OnKeyUp(e);
          if (_sdlWindow == IntPtr.Zero) return;
  
          var sdlKey = ConvertAvaloniaKeyToSdl(e.Key);
          if (sdlKey != SDL.SDL_Keycode.SDLK_UNKNOWN)
          {
              var sdlEvent = new SDL.SDL_Event
              {
                  key = new SDL.SDL_KeyboardEvent
                  {
                      type = SDL.SDL_EventType.SDL_KEYUP,
                      windowID = SDL.SDL_GetWindowID(_sdlWindow),
                      keysym = new SDL.SDL_Keysym
                      {
                          sym = sdlKey,
                          mod = ConvertAvaloniaModifiersToSdl(e.KeyModifiers)
                      }
                  }
              };
              SDL.SDL_PushEvent(ref sdlEvent);
              e.Handled = true;
          }
      }
  
      // 转换Avalonia按键到SDL按键码，需补充所有需要支持的按键映射
      private SDL.SDL_Keycode ConvertAvaloniaKeyToSdl(Key avaloniaKey)
      {
          return avaloniaKey switch
          {
              Key.A => SDL.SDL_Keycode.SDLK_a,
              Key.B => SDL.SDL_Keycode.SDLK_b,
              Key.Left => SDL.SDL_Keycode.SDLK_LEFT,
              Key.Right => SDL.SDL_Keycode.SDLK_RIGHT,
              Key.Up => SDL.SDL_Keycode.SDLK_UP,
              Key.Down => SDL.SDL_Keycode.SDLK_DOWN,
              Key.Space => SDL.SDL_Keycode.SDLK_SPACE,
              _ => SDL.SDL_Keycode.SDLK_UNKNOWN
          };
      }
  
      // 转换Avalonia修饰键到SDL修饰符
      private SDL.SDL_Keymod ConvertAvaloniaModifiersToSdl(KeyModifiers modifiers)
      {
          SDL.SDL_Keymod sdlMod = 0;
          if ((modifiers & KeyModifiers.Control) != 0)
              sdlMod |= SDL.SDL_Keymod.KMOD_CTRL;
          if ((modifiers & KeyModifiers.Shift) != 0)
              sdlMod |= SDL.SDL_Keymod.KMOD_SHIFT;
          if ((modifiers & KeyModifiers.Alt) != 0)
              sdlMod |= SDL.SDL_Keymod.KMOD_ALT;
          return sdlMod;
      }
  }
  

• 关联SDL窗口句柄
  创建SDL窗口后，调用SetSdlWindow方法将SDL窗口句柄传递给NativeEmbeddingControl：

  IntPtr windowPtr = SDL.SDL_CreateWindowFrom(windowHandle);
  nativeEmbeddingControl.SetSdlWindow(windowPtr);
  

• 确保控件获得焦点
  在控件加载完成时调用Focus()方法，确保键盘事件能被NativeEmbeddingControl捕获：

  nativeEmbeddingControl.Focus();
  

注意：如果你的SDL应用使用了SDL_SetEventFilter，需确保过滤器不会丢弃手动推送的键盘事件。

内容的提问来源于stack exchange，提问作者gryz