From eae12e6f2321f2f91c35463a808e335312fbc4e1 Mon Sep 17 00:00:00 2001
From: WinterSnowfall <WinterSnowfall@users.noreply.github.com>
Date: Fri, 4 Oct 2024 16:50:43 +0300
Subject: [PATCH] [d3d8] Cache all back buffers for additional swapchains

---
 src/d3d8/d3d8_device.cpp  |  2 +-
 src/d3d8/d3d8_swapchain.h | 17 +++++++++--------
 2 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/src/d3d8/d3d8_device.cpp b/src/d3d8/d3d8_device.cpp
index 154c4f075..a41a71af2 100644
--- a/src/d3d8/d3d8_device.cpp
+++ b/src/d3d8/d3d8_device.cpp
@@ -219,7 +219,7 @@ namespace dxvk {
     );
 
     if (likely(SUCCEEDED(res)))
-      *ppSwapChain = ref(new D3D8SwapChain(this, std::move(pSwapChain9)));
+      *ppSwapChain = ref(new D3D8SwapChain(this, pPresentationParameters, std::move(pSwapChain9)));
 
     return res;
   }
diff --git a/src/d3d8/d3d8_swapchain.h b/src/d3d8/d3d8_swapchain.h
index b356873e0..ef2b41f64 100644
--- a/src/d3d8/d3d8_swapchain.h
+++ b/src/d3d8/d3d8_swapchain.h
@@ -13,38 +13,39 @@ namespace dxvk {
 
     D3D8SwapChain(
       D3D8Device*                      pDevice,
+      D3DPRESENT_PARAMETERS*           pPresentationParameters,
       Com<d3d9::IDirect3DSwapChain9>&& pSwapChain)
-      : D3D8SwapChainBase(pDevice, std::move(pSwapChain)) {}
+      : D3D8SwapChainBase(pDevice, std::move(pSwapChain)) {
+        m_backBuffers.resize(pPresentationParameters->BackBufferCount);
+    }
 
     HRESULT STDMETHODCALLTYPE Present(const RECT *src, const RECT *dst, HWND hWnd, const RGNDATA *dirtyRegion) final {
         return GetD3D9()->Present(src, dst, hWnd, dirtyRegion, 0);
     }
     
     HRESULT STDMETHODCALLTYPE GetBackBuffer(UINT BackBuffer, D3DBACKBUFFER_TYPE Type, IDirect3DSurface8** ppBackBuffer) final {
-      InitReturnPtr(ppBackBuffer);
-
       if (unlikely(ppBackBuffer == nullptr))
         return D3DERR_INVALIDCALL;
 
       // Same logic as in D3D8Device::GetBackBuffer
-      if (unlikely(m_backBuffer == nullptr)) {
+      if (BackBuffer >= m_backBuffers.size() || m_backBuffers[BackBuffer] == nullptr) {
         Com<d3d9::IDirect3DSurface9> pSurface9;
         HRESULT res = GetD3D9()->GetBackBuffer(BackBuffer, (d3d9::D3DBACKBUFFER_TYPE)Type, &pSurface9);
 
         if (likely(SUCCEEDED(res))) {
-          m_backBuffer = new D3D8Surface(GetParent(), std::move(pSurface9));
-          *ppBackBuffer = m_backBuffer.ref();
+          m_backBuffers[BackBuffer] = new D3D8Surface(GetParent(), std::move(pSurface9));
+          *ppBackBuffer = m_backBuffers[BackBuffer].ref();
         }
 
         return res;
       }
 
-      *ppBackBuffer = m_backBuffer.ref();
+      *ppBackBuffer = m_backBuffers[BackBuffer].ref();
       return D3D_OK;
     }
 
   private:
-    Com<D3D8Surface> m_backBuffer = nullptr;
+    std::vector<Com<D3D8Surface, false>> m_backBuffers;
 
   };