进程窗口重定向与自定义处理可行性咨询：如何实现类似Xbox GameBar的程序嵌入功能

Absolutely, this is totally achievable on Windows using a mix of Win32 APIs, modern composition frameworks, or offscreen rendering techniques. Here's a breakdown of practical approaches tailored to your requirements:

1. Win32 Hidden Window + Cross-Process Canvas Sharing #

This is the most straightforward approach if you're working with traditional Win32-based apps:

• Create an invisible, taskbar-less window for the external process:
  When calling CreateWindowEx, use the WS_EX_TOOLWINDOW extended style (this hides it from the taskbar) plus WS_HIDDEN to keep it off-screen. You can explicitly set the window size via the nWidth and nHeight parameters.

  HWND hiddenWindow = CreateWindowEx(
      WS_EX_TOOLWINDOW | WS_EX_NOACTIVATE,
      L"HiddenWidgetClass",
      L"",
      WS_HIDDEN,
      0, 0, 800, 600, // Your desired width/height
      NULL, NULL, hInstance, NULL
  );
  

• Share the rendering canvas between processes:
  For GDI-based rendering, you can share the window's device context (DC) via GetDC(hiddenWindow) and pass the DC handle to your main app using inter-process communication (IPC) like named pipes or shared memory. For DirectX/OpenGL, create a swap chain bound to the hidden window, then share the back buffer texture using IDXGIResource1::CreateSharedHandle.
• Render in your main app:
  Use BitBlt (for GDI) or copy the shared texture to your main app's rendering surface to display the external widget's content.

2. DirectComposition + Offscreen Rendering #

If you want a more modern, performant approach (similar to how Xbox GameBar works):

• External process renders offscreen:
  Skip creating a visible window entirely. Instead, create a Direct3D device and an offscreen texture (or swap chain without a window). This process won't show up in the taskbar at all since it has no window handle.
• Share the rendering surface:
  Create a shared handle for the offscreen texture using CreateSharedHandle, then pass this handle to your main app via IPC.
• Compose into your main window:
  Use DirectComposition in your main app to create a Visual that references the shared texture, then add this visual to your main window's composition tree. This gives you smooth, hardware-accelerated rendering without any visible sub-process windows.

3. Xaml Islands (for WinUI/WPF/WinForms Apps) #

If your main app uses modern UI frameworks like WinUI 3, WPF, or WinForms:

• Package the widget as a WinUI component:
  Build your external widget as a WinUI 3 class library. The component runs in a separate process but doesn't create its own visible window.
• Embed using Xaml Islands:
  In your main app, use WindowsXamlHost (for WinForms/WPF) or DesktopWindowXamlSource (for WinUI 3) to host the external widget component. The system handles rendering synchronization, and the widget process won't appear in the taskbar.

Key Tips to Avoid Pitfalls #

• IPC Sync: Use events (like CreateEvent) to signal when the external process has finished rendering a frame—this prevents your main app from drawing incomplete content.
• Permission Handling: Ensure both processes run under the same user context (or with appropriate admin rights) to avoid access denied errors when sharing handles/textures.
• Cleanup: Properly destroy shared resources and terminate the external process when your main app closes to prevent memory leaks.

内容的提问来源于stack exchange，提问作者BierDav