dxgi: cache shared handles instead of re-creating them

This will cache up to 10 handles, in practice I have never seen DXGI
return anything but the same resource each time but we allow for more
anyway should MS change something in the future.

Should the cache get over filled it is disabled entirely and we revert
to the original behaviour.

host/platform/Windows/capture/DXGI/src/d3d12.c

@@ -26,6 +26,7 @@
 #include "common/debug.h"
 #include "common/option.h"
 #include "common/windebug.h"
+#include "common/array.h"
 #include "ods_capture.h"
 
 #define ALIGN_TO(value, align) (((value) + (align) - 1) & -(align))
@@ -52,6 +53,15 @@ struct D3D12Backend
   UINT64                fenceValue;
   ID3D12Fence         * fence;
   HANDLE                event;
+
+  // shared handle cache
+  struct
+  {
+    ID3D11Texture2D * tex;
+    HANDLE            handle;
+  }
+  handleCache[10];
+  int handleCacheCount;
 };
 
 static struct DXGIInterface * dxgi = NULL;
@@ -289,6 +299,9 @@ static void d3d12_free(void)
   if (this->src)
     ID3D12Resource_Release(this->src);
 
+  for(int i = 0; i < this->handleCacheCount; ++i)
+    CloseHandle(this->handleCache[i].handle);
+
   if (this->commandQueue)
     ID3D12CommandQueue_Release(this->commandQueue);
 
@@ -309,6 +322,21 @@ static bool d3d12_copyFrame(Texture * parent, ID3D11Texture2D * src)
   if (this->copySleep > 0)
     Sleep(this->copySleep);
 
+  HANDLE handle = INVALID_HANDLE_VALUE;
+
+  if (this->handleCacheCount > -1)
+  {
+    // see if there is a cached handle already available for this texture
+    for(int i = 0; i < this->handleCacheCount; ++i)
+      if (this->handleCache[i].tex == src)
+      {
+        handle = this->handleCache[i].handle;
+        break;
+      }
+  }
+
+  if (handle == INVALID_HANDLE_VALUE)
+  {
     status = ID3D11Texture2D_QueryInterface(src, &IID_IDXGIResource1, (void **)&res1);
     if (FAILED(status))
     {
@@ -316,7 +344,6 @@ static bool d3d12_copyFrame(Texture * parent, ID3D11Texture2D * src)
       return CAPTURE_RESULT_ERROR;
     }
 
-  HANDLE handle;
     status = IDXGIResource1_CreateSharedHandle(res1, NULL, DXGI_SHARED_RESOURCE_READ, NULL, &handle);
     if (FAILED(status))
     {
@@ -325,17 +352,33 @@ static bool d3d12_copyFrame(Texture * parent, ID3D11Texture2D * src)
       goto cleanup;
     }
 
+    // store the handle for later use
+    if (this->handleCacheCount < ARRAY_LENGTH(this->handleCache))
+    {
+      this->handleCache[this->handleCacheCount].tex    = src;
+      this->handleCache[this->handleCacheCount].handle = handle;
+      ++this->handleCacheCount;
+    }
+    else
+    {
+      // too many handles to cache, disable the cache entirely
+      for(int i = 0; i < this->handleCacheCount; ++i)
+        CloseHandle(this->handleCache[i].handle);
+      this->handleCacheCount = -1;
+    }
+  }
+
   status = ID3D12Device_OpenSharedHandle(this->device, handle, &IID_ID3D12Resource, (void **)&this->src);
+  if (this->handleCacheCount == -1)
+    CloseHandle(handle);
+
   if (FAILED(status))
   {
     DEBUG_WINERROR("Failed to get create shared handle for texture", status);
-    CloseHandle(handle);
     fail = true;
     goto cleanup;
   }
 
-  CloseHandle(handle);
-
   D3D12_TEXTURE_COPY_LOCATION srcLoc = {
     .pResource        = this->src,
     .Type             = D3D12_TEXTURE_COPY_TYPE_SUBRESOURCE_INDEX,