From da7d6b4011be6b512a859574594d4159fe6b004b Mon Sep 17 00:00:00 2001
From: Geoffrey McRae <geoff@hostfission.com>
Date: Thu, 6 Aug 2026 11:39:44 +1000
Subject: [PATCH] [idd] capture: defer interop synchronization

Signal the shared D3D11 source only after a retained candidate and its
command slots have been acquired. Superseded source frames no longer queue
a fence that no Direct3D 12 work will consume.
---
 idd/LGIdd/CSwapChainProcessor.cpp | 29 ++++++++++++++++++-----------
 1 file changed, 18 insertions(+), 11 deletions(-)

diff --git a/idd/LGIdd/CSwapChainProcessor.cpp b/idd/LGIdd/CSwapChainProcessor.cpp
index 6415337a..cab09002 100644
--- a/idd/LGIdd/CSwapChainProcessor.cpp
+++ b/idd/LGIdd/CSwapChainProcessor.cpp
@@ -1403,17 +1403,6 @@ bool CSwapChainProcessor::SwapChainNewFrame(ComPtr<IDXGIResource> acquiredBuffer
     return false;
   }
 
-  /**
-   * Even though we have not performed any copy/draw operations we still need to
-   * use a fence. Because we share this texture with DirectX12 it is able to
-   * read from it before the desktop duplication API has finished updating it.
-   */
-  if (!srcRes->Signal())
-  {
-    SetFullPendingDamage();
-    return false;
-  }
-
   RECT dirtyRects[LG_MAX_DIRTY_RECTS] = {0};
   bool noImageUpdate = false;
   if (moveRegionCount || dirtyRectCount > ARRAYSIZE(dirtyRects))
@@ -1688,7 +1677,25 @@ bool CSwapChainProcessor::SwapChainNewFrame(ComPtr<IDXGIResource> acquiredBuffer
       SetFullPendingDamage();
       return false;
     }
+  }
 
+  /**
+   * Even though we have not performed any copy/draw operations we still need
+   * to use a fence. Because we share this texture with DirectX12 it is able to
+   * read from it before IddCx has finished updating it.
+   */
+  if (!srcRes->Signal())
+  {
+    if (computeSlot)
+      computeSlot->Cancel();
+    copySlot->Cancel();
+    ReleaseCandidate(candidateIndex);
+    SetFullPendingDamage();
+    return false;
+  }
+
+  if (computeSlot)
+  {
     if (!srcRes->Sync(*computeSlot))
     {
       computeSlot->Cancel();