From 92040f4636c8a65c17cc8dbd8e664c9409ed3cb3 Mon Sep 17 00:00:00 2001
From: baldurk <baldurk@baldurk.org>
Date: Sun, 20 Sep 2020 11:23:06 +0100
Subject: [PATCH] Fix a crash with D3D11 SWAP_EFFECT_FLIP_DISCARD swapchains.
 Closes #2055

* DXGI is entangled with the API unfortunately, such that for D3D11
  DXGI_SWAP_EFFECT_FLIP_DISCARD can only access buffer 0 (like
  DXGI_SWAP_EFFECT_DISCARD) but for D3D12 it can access any buffer. This is
  naturally undocumented.
---
 renderdoc/driver/dxgi/dxgi_wrapped.cpp | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/renderdoc/driver/dxgi/dxgi_wrapped.cpp b/renderdoc/driver/dxgi/dxgi_wrapped.cpp
index b81bc42cf..643379492 100644
--- a/renderdoc/driver/dxgi/dxgi_wrapped.cpp
+++ b/renderdoc/driver/dxgi/dxgi_wrapped.cpp
@@ -365,8 +365,13 @@ void WrappedIDXGISwapChain4::WrapBuffersAfterResize()
 
   int bufCount = desc.BufferCount;
 
-  if(desc.SwapEffect == DXGI_SWAP_EFFECT_DISCARD)
+  // discard swap effects only allow querying buffer 0, but only on D3D11 - on D3D12 they can (and
+  // must) still query the full set of buffers.
+  if(m_pDevice->GetFrameCapturer()->GetFrameCaptureDriver() == RDCDriver::D3D11 &&
+     (desc.SwapEffect == DXGI_SWAP_EFFECT_DISCARD || desc.SwapEffect == DXGI_SWAP_EFFECT_FLIP_DISCARD))
+  {
     bufCount = 1;
+  }
 
   RDCASSERT(bufCount < MAX_NUM_BACKBUFFERS);