From 9bded745439caedd4d86cc46a571597198215f75 Mon Sep 17 00:00:00 2001
From: Quantum <quantum2048@gmail.com>
Date: Wed, 11 Aug 2021 02:43:42 -0400
Subject: [PATCH] [host] dxgi: use CopySubresourceRegion when possible

This commit adds damage tracking to the DXGI textures, and only copies the
damaged areas to the textures with ID3D11DeviceContext::CopySubresourceRegion.

The sleep logic in waitFrame makes it difficult for this to reduce the
latency, but removing it shows significant improvements (6-7 ms to ~3 ms)
when a tiny portion of the screen is damaged, while showing no difference on
full screen damage.
---
 host/platform/Windows/capture/DXGI/src/dxgi.c | 53 +++++++++++++++++--
 1 file changed, 49 insertions(+), 4 deletions(-)

diff --git a/host/platform/Windows/capture/DXGI/src/dxgi.c b/host/platform/Windows/capture/DXGI/src/dxgi.c
index 72a24163..f28c33af 100644
--- a/host/platform/Windows/capture/DXGI/src/dxgi.c
+++ b/host/platform/Windows/capture/DXGI/src/dxgi.c
@@ -40,7 +40,7 @@
 
 #include "dxgi_extra.h"
 
-#define LOCKED(x) INTERLOCKED_SECTION(this->deviceContextLock, x)
+#define LOCKED(...) INTERLOCKED_SECTION(this->deviceContextLock, __VA_ARGS__)
 
 enum TextureState
 {
@@ -56,8 +56,10 @@ typedef struct Texture
   ID3D11Texture2D          * tex;
   D3D11_MAPPED_SUBRESOURCE   map;
   uint64_t                   copyTime;
-  uint8_t                    damageRectsCount;
+  uint32_t                   damageRectsCount;
   FrameDamageRect            damageRects[KVMFR_MAX_DAMAGE_RECTS];
+  int32_t                    texDamageCount;
+  FrameDamageRect            texDamageRects[KVMFR_MAX_DAMAGE_RECTS];
 }
 Texture;
 
@@ -556,6 +558,7 @@ static bool dxgi_init(void)
 
   for (int i = 0; i < this->maxTextures; ++i)
   {
+    this->texture[i].texDamageCount = -1;
     status = ID3D11Device_CreateTexture2D(this->device, &texDesc, NULL, &this->texture[i].tex);
     if (FAILED(status))
     {
@@ -859,10 +862,36 @@ static CaptureResult dxgi_capture(void)
       {
         computeFrameDamage(tex);
 
+        if (tex->texDamageCount < 0 || tex->damageRectsCount == 0 ||
+            tex->texDamageCount + tex->damageRectsCount > KVMFR_MAX_DAMAGE_RECTS)
+          tex->texDamageCount = -1;
+        else
+        {
+          memcpy(tex->texDamageRects + tex->texDamageCount, tex->damageRects,
+            tex->damageRectsCount * sizeof(FrameDamageRect));
+          tex->texDamageCount += tex->damageRectsCount;
+          tex->texDamageCount = rectsMergeOverlapping(tex->texDamageRects, tex->texDamageCount);
+        }
+
         // issue the copy from GPU to CPU RAM
         tex->copyTime = microtime();
-        ID3D11DeviceContext_CopyResource(this->deviceContext,
-          (ID3D11Resource *)tex->tex, (ID3D11Resource *)src);
+        if (tex->texDamageCount < 0)
+          ID3D11DeviceContext_CopyResource(this->deviceContext,
+            (ID3D11Resource *)tex->tex, (ID3D11Resource *)src);
+        else
+        {
+          for (int i = 0; i < tex->texDamageCount; ++i)
+          {
+            FrameDamageRect * rect = tex->texDamageRects + i;
+            D3D11_BOX box = {
+              .left = rect->x, .top = rect->y, .front = 0, .back = 1,
+              .right = rect->x + rect->width, .bottom = rect->y + rect->height,
+            };
+            ID3D11DeviceContext_CopySubresourceRegion(this->deviceContext,
+              (ID3D11Resource *)tex->tex, 0, rect->x, rect->y, 0,
+              (ID3D11Resource *)src, 0, &box);
+          }
+        }
       }
 
       if (copyPointer)
@@ -879,6 +908,22 @@ static CaptureResult dxgi_capture(void)
     {
       ID3D11Texture2D_Release(src);
 
+      for (int i = 0; i < this->maxTextures; ++i)
+      {
+        Texture * t = this->texture + i;
+        if (i == this->texWIndex)
+          t->texDamageCount = 0;
+        else if (tex->damageRectsCount > 0 && t->texDamageCount >= 0 &&
+                 t->texDamageCount + tex->damageRectsCount <= KVMFR_MAX_DAMAGE_RECTS)
+        {
+          memcpy(t->texDamageRects + t->texDamageCount, tex->damageRects,
+            tex->damageRectsCount * sizeof(FrameDamageRect));
+          t->texDamageCount += tex->damageRectsCount;
+        }
+        else
+          t->texDamageCount = -1;
+      }
+
       // set the state, and signal
       tex->state     = TEXTURE_STATE_PENDING_MAP;
       tex->formatVer = this->formatVer;