From 770bce4ec0f757b66d403162fd8ce75878739c02 Mon Sep 17 00:00:00 2001
From: Geoffrey McRae <geoff@hostfission.com>
Date: Thu, 6 Aug 2026 05:04:22 +1000
Subject: [PATCH] [idd] adapter: defer render selection until initialization

---
 idd/LGIdd/CIndirectDeviceContext.cpp | 41 ++++++++++++++++------------
 idd/LGIdd/CIndirectDeviceContext.h   | 19 +++++++------
 idd/LGIdd/Device.cpp                 |  2 +-
 3 files changed, 35 insertions(+), 27 deletions(-)

diff --git a/idd/LGIdd/CIndirectDeviceContext.cpp b/idd/LGIdd/CIndirectDeviceContext.cpp
index cca6d999..472cc19b 100644
--- a/idd/LGIdd/CIndirectDeviceContext.cpp
+++ b/idd/LGIdd/CIndirectDeviceContext.cpp
@@ -315,8 +315,8 @@ void CIndirectDeviceContext::InitAdapter()
   // Select the render adapter before advertising capabilities. If no hardware
   // adapter is available, this is a software-rendered display and must remain
   // SDR-only; the software path must never depend on compute processing.
-  bool havePreferredRenderAdapter = false;
-  LUID preferredRenderAdapter = {};
+  m_havePreferredRenderAdapter = false;
+  m_preferredRenderAdapter     = {};
   IDXGIFactory1 * factory = NULL;
   HRESULT factoryStatus = CreateDXGIFactory1(
     __uuidof(IDXGIFactory1), (void **)&factory);
@@ -362,15 +362,15 @@ void CIndirectDeviceContext::InitAdapter()
 
       DEBUG_INFO("Selected render adapter %ls (vendor 0x%04x, device 0x%04x)",
         adapterDesc.Description, adapterDesc.VendorId, adapterDesc.DeviceId);
-      preferredRenderAdapter = adapterDesc.AdapterLuid;
-      havePreferredRenderAdapter = true;
+      m_preferredRenderAdapter     = adapterDesc.AdapterLuid;
+      m_havePreferredRenderAdapter = true;
       break;
     }
 
     factory->Release();
   }
 
-  m_softwareMode = !havePreferredRenderAdapter;
+  m_softwareMode = !m_havePreferredRenderAdapter;
   if (m_softwareMode)
     DEBUG_INFO("No hardware render adapter available; using SDR software mode");
 
@@ -471,21 +471,10 @@ void CIndirectDeviceContext::InitAdapter()
     return;
   }
 
-  DEBUG_INFO("IddCxAdapterInitAsync started successfully (adapter %p)",
-    m_adapter);
-
-  // Try to co-exist with the virtual video device by telling IddCx which
-  // hardware adapter we prefer to render on.
-  if (havePreferredRenderAdapter)
-  {
-    IDARG_IN_ADAPTERSETRENDERADAPTER args = {};
-    args.PreferredRenderAdapter = preferredRenderAdapter;
-    IddCxAdapterSetRenderAdapter(m_adapter, &args);
-    DEBUG_INFO("Preferred render adapter set");
-  }
-
   auto * wrapper = WdfObjectGet_CIndirectDeviceContextWrapper(m_adapter);
   wrapper->context = this;
+  DEBUG_INFO("IddCxAdapterInitAsync started successfully (adapter %p)",
+    m_adapter);
   DEBUG_INFO("Adapter context attached; waiting for initialization callback");
 
   // Adapter is up; no need to keep retrying.
@@ -494,6 +483,22 @@ void CIndirectDeviceContext::InitAdapter()
   DEBUG_INFO("Adapter initialization request complete; returning to IddCx");
 }
 
+void CIndirectDeviceContext::FinishAdapterInit(UINT connectorIndex)
+{
+  // Try to co-exist with the virtual video device by telling IddCx which
+  // hardware adapter we prefer to render on. Do this only after the adapter
+  // has finished initializing, but before adding its monitor.
+  if (m_havePreferredRenderAdapter)
+  {
+    IDARG_IN_ADAPTERSETRENDERADAPTER args = {};
+    args.PreferredRenderAdapter = m_preferredRenderAdapter;
+    IddCxAdapterSetRenderAdapter(m_adapter, &args);
+    DEBUG_INFO("Preferred render adapter set");
+  }
+
+  FinishInit(connectorIndex);
+}
+
 void CIndirectDeviceContext::FinishInit(UINT connectorIndex)
 {
   DEBUG_INFO("Creating monitor on connector %u", connectorIndex);
diff --git a/idd/LGIdd/CIndirectDeviceContext.h b/idd/LGIdd/CIndirectDeviceContext.h
index 87019877..cb0afb8c 100644
--- a/idd/LGIdd/CIndirectDeviceContext.h
+++ b/idd/LGIdd/CIndirectDeviceContext.h
@@ -64,14 +64,16 @@ class CIndirectDeviceContext
 {
 private:
   WDFDEVICE     m_wdfDevice;
-  IDDCX_ADAPTER m_adapter       = nullptr;
-  IDDCX_MONITOR m_monitor       = nullptr;
-  bool          m_replugMonitor = false;
-  bool          m_replugPending = false;
-  bool          m_monitorDeparted = false;
-  bool          m_swapChainAssigned = false;
-  bool          m_swapChainReady = false;
-  bool          m_waitForSwapChainRelease = false;
+  IDDCX_ADAPTER m_adapter                    = nullptr;
+  IDDCX_MONITOR m_monitor                    = nullptr;
+  LUID          m_preferredRenderAdapter     = {};
+  bool          m_havePreferredRenderAdapter = false;
+  bool          m_replugMonitor              = false;
+  bool          m_replugPending              = false;
+  bool          m_monitorDeparted            = false;
+  bool          m_swapChainAssigned          = false;
+  bool          m_swapChainReady             = false;
+  bool          m_waitForSwapChainRelease    = false;
 
   // Guards the adapter/monitor init handshake and the replug state machine
   // (monitor/replug/swap-chain state, m_doSetMode, m_setMode). These are
@@ -227,6 +229,7 @@ public:
 
   bool PopulateDefaultModes();
   void InitAdapter();
+  void FinishAdapterInit(UINT connectorIndex);
   void FinishInit(UINT connectorIndex);
   void ReplugMonitor();
 
diff --git a/idd/LGIdd/Device.cpp b/idd/LGIdd/Device.cpp
index ca7b5482..e8f44c7b 100644
--- a/idd/LGIdd/Device.cpp
+++ b/idd/LGIdd/Device.cpp
@@ -92,7 +92,7 @@ NTSTATUS LGIddAdapterInitFinished(IDDCX_ADAPTER adapter, const IDARG_IN_ADAPTER_
   }
 
   DEBUG_INFO("Adapter initialized, creating monitor");
-  wrapper->context->FinishInit(0);
+  wrapper->context->FinishAdapterInit(0);
   return STATUS_SUCCESS;
 }