[idd] skip copies for static frames

Treat IddCx's single empty dirty rectangle as no image update instead
of promoting it to full damage.

Preserve pending damage and format changes, and fall back to full damage
when legacy move regions are present.

idd/LGIdd/CInteropResource.cpp

@@ -154,6 +154,7 @@ void CInteropResource::SetDirtyRects(const RECT * dirtyRects, unsigned nbDirtyRe
     return;
   }
 
-  memcpy(m_dirtyRects, dirtyRects, nbDirtyRects * sizeof(*m_dirtyRects));
+  if (nbDirtyRects)
+    memcpy(m_dirtyRects, dirtyRects, nbDirtyRects * sizeof(*m_dirtyRects));
   m_nbDirtyRects = nbDirtyRects;
 }

idd/LGIdd/CSwapChainProcessor.cpp

@@ -44,6 +44,23 @@ static uint64_t Nanotime()
     ticks % frequency * 1000000000ULL / frequency;
 }
 
+static bool FrameMetadataChanged(const D12FrameFormat& previous,
+  const D12FrameFormat& current)
+{
+  return
+    previous.hdrMetadata   != current.hdrMetadata   ||
+    previous.sdrWhiteLevel != current.sdrWhiteLevel ||
+    (current.hdrMetadata &&
+      (memcmp(previous.displayPrimary, current.displayPrimary,
+         sizeof(current.displayPrimary)) != 0 ||
+       memcmp(previous.whitePoint, current.whitePoint,
+         sizeof(current.whitePoint)) != 0 ||
+       previous.maxDisplayLuminance       != current.maxDisplayLuminance       ||
+       previous.minDisplayLuminance       != current.minDisplayLuminance       ||
+       previous.maxContentLightLevel      != current.maxContentLightLevel      ||
+       previous.maxFrameAverageLightLevel != current.maxFrameAverageLightLevel));
+}
+
 CSwapChainProcessor::CSwapChainProcessor(CIndirectMonitorContext * monitorContext,
     UINT64 assignmentGeneration, IDDCX_MONITOR monitor,
     CIndirectDeviceContext* devContext, IDDCX_SWAPCHAIN hSwapChain,
@@ -199,8 +216,9 @@ bool CSwapChainProcessor::SwapChainThreadCore()
     if (WaitForSingleObject(m_terminateEvent.Get(), 0) == WAIT_OBJECT_0)
       break;
 
-    UINT frameNumber = 0;
-    UINT dirtyRectCount = 0;
+    UINT frameNumber     = 0;
+    UINT dirtyRectCount  = 0;
+    UINT moveRegionCount = 0;
     ComPtr<IDXGIResource> surface;
 
     // The surface colour space is the source of truth for the content format.
@@ -240,9 +258,10 @@ bool CSwapChainProcessor::SwapChainThreadCore()
       hr = IddCxSwapChainReleaseAndAcquireBuffer(m_hSwapChain, &buffer);
       if (SUCCEEDED(hr))
       {
-        frameNumber = buffer.MetaData.PresentationFrameNumber;
-        dirtyRectCount = buffer.MetaData.DirtyRectCount;
-        surface = buffer.MetaData.pSurface;
+        frameNumber     = buffer.MetaData.PresentationFrameNumber;
+        dirtyRectCount  = buffer.MetaData.DirtyRectCount;
+        moveRegionCount = buffer.MetaData.MoveRegionCount;
+        surface         = buffer.MetaData.pSurface;
       }
     }
 
@@ -269,8 +288,8 @@ bool CSwapChainProcessor::SwapChainThreadCore()
       if (frameNumber != lastFrameNumber)
       {
         lastFrameNumber = frameNumber;
-        if (!SwapChainNewFrame(surface, dirtyRectCount, colorSpace,
-              sdrWhiteLevel, Nanotime() - captureStart))
+        if (!SwapChainNewFrame(surface, dirtyRectCount, moveRegionCount,
+              colorSpace, sdrWhiteLevel, Nanotime() - captureStart))
           DEBUG_WARN("Failed to submit frame");
       }
 
@@ -494,8 +513,9 @@ bool CSwapChainProcessor::GetContentHDRMetadata(D12FrameFormat& format) const
 }
 
 bool CSwapChainProcessor::SwapChainNewFrame(ComPtr<IDXGIResource> acquiredBuffer,
-  unsigned dirtyRectCount, DXGI_COLOR_SPACE_TYPE colorSpace,
-  UINT sdrWhiteLevel, uint64_t captureTime)
+  unsigned dirtyRectCount, unsigned moveRegionCount,
+  DXGI_COLOR_SPACE_TYPE colorSpace, UINT sdrWhiteLevel,
+  uint64_t captureTime)
 {
   // Preserve the fast drop path: never hold an IddCx frame while waiting for
   // a slow or disconnected client. We have not read its rectangles, so force
@@ -533,8 +553,11 @@ bool CSwapChainProcessor::SwapChainNewFrame(ComPtr<IDXGIResource> acquiredBuffer
   srcRes->Signal();
 
   RECT dirtyRects[LG_MAX_DIRTY_RECTS] = {0};
-  if (dirtyRectCount > ARRAYSIZE(dirtyRects))
+  bool noImageUpdate = false;
+  if (moveRegionCount || dirtyRectCount > ARRAYSIZE(dirtyRects))
   {
+    // Move regions are not represented by the dirty rectangle list. Copy the
+    // full surface so the alternating destinations remain coherent.
     srcRes->SetFullDamage();
   }
   else
@@ -550,13 +573,23 @@ bool CSwapChainProcessor::SwapChainNewFrame(ComPtr<IDXGIResource> acquiredBuffer
       DEBUG_ERROR_HR(hr, "IddCxSwapChainGetDirtyRects Failed");
       srcRes->SetFullDamage();
     }
+    else if (dirtyOut.DirtyRectOutCount == 1 &&
+        dirtyRects[0].left   == 0 && dirtyRects[0].top    == 0 &&
+        dirtyRects[0].right  == 0 && dirtyRects[0].bottom == 0)
+    {
+      // One empty rectangle is IddCx's static-desktop re-encode marker. It
+      // does not describe an image update and must not become full damage.
+      noImageUpdate = true;
+      srcRes->SetDirtyRects(nullptr, 0);
+    }
     else
       srcRes->SetDirtyRects(dirtyRects, dirtyOut.DirtyRectOutCount);
   }
 
   D3D12_RESOURCE_DESC srcDesc = srcRes->GetRes()->GetDesc();
-  AccumulateFrameDamage(
-    srcRes->GetDirtyRects(), srcRes->GetDirtyRectCount());
+  if (!noImageUpdate)
+    AccumulateFrameDamage(
+      srcRes->GetDirtyRects(), srcRes->GetDirtyRectCount());
 
   // Never hold an IddCx frame waiting for a slow or disconnected client. Read
   // and retain its damage first so the next published frame remains complete.
@@ -564,11 +597,11 @@ bool CSwapChainProcessor::SwapChainNewFrame(ComPtr<IDXGIResource> acquiredBuffer
     return true;
 
   D12FrameFormat srcFormat = {};
-  srcFormat.desc          = srcDesc;
-  srcFormat.width         = (unsigned)srcDesc.Width;
-  srcFormat.height        = srcDesc.Height;
-  srcFormat.format        = GetFrameType(srcDesc.Format);
-  srcFormat.sdrWhiteLevel = sdrWhiteLevel;
+  srcFormat.desc           = srcDesc;
+  srcFormat.width          = (unsigned)srcDesc.Width;
+  srcFormat.height         = srcDesc.Height;
+  srcFormat.format         = GetFrameType(srcDesc.Format);
+  srcFormat.sdrWhiteLevel  = sdrWhiteLevel;
   srcFormat.colorTransform = m_devContext->GetColorTransform();
 
   switch (colorSpace)
@@ -643,6 +676,8 @@ bool CSwapChainProcessor::SwapChainNewFrame(ComPtr<IDXGIResource> acquiredBuffer
       break;
   }
 
+  const bool frameMetadataChanged = noImageUpdate &&
+    FrameMetadataChanged(m_postProcessor.GetOutputFormat(), srcFormat);
   bool postProcessFormatChanged = false;
   if (!m_postProcessor.Configure(srcFormat, &postProcessFormatChanged))
     return false;
@@ -652,6 +687,11 @@ bool CSwapChainProcessor::SwapChainNewFrame(ComPtr<IDXGIResource> acquiredBuffer
     m_nbDirtyRects = 0;
     SetFullPendingDamage();
   }
+  else if (frameMetadataChanged)
+    SetFullPendingDamage();
+
+  if (noImageUpdate && !m_hasPendingDamage)
+    return true;
 
   const D12FrameFormat& dstFormat = m_postProcessor.GetOutputFormat();
 

idd/LGIdd/CSwapChainProcessor.h

@@ -101,8 +101,10 @@ private:
   void UpdateHDRMetadata(const IDDCX_METADATA2& metadata);
 #endif
   bool GetContentHDRMetadata(D12FrameFormat& format) const;
-  bool SwapChainNewFrame(ComPtr<IDXGIResource> acquiredBuffer, unsigned dirtyRectCount,
-    DXGI_COLOR_SPACE_TYPE colorSpace, UINT sdrWhiteLevel, uint64_t captureTime);
+  bool SwapChainNewFrame(ComPtr<IDXGIResource> acquiredBuffer,
+    unsigned dirtyRectCount, unsigned moveRegionCount,
+    DXGI_COLOR_SPACE_TYPE colorSpace, UINT sdrWhiteLevel,
+    uint64_t captureTime);
 
 public:
   CSwapChainProcessor(CIndirectMonitorContext * monitorContext, UINT64 assignmentGeneration,