preview window flipped

config/runtime-host.json

@@ -11,6 +11,6 @@
   "autoReload": true,
   "maxTemporalHistoryFrames": 12,
   "previewEnabled": true,
-  "previewFps": 30,
+  "previewFps": 59.94,
   "enableExternalKeying": true
 }

src/README.md

@@ -208,7 +208,7 @@ Currently consumed fields:
 - `previewFps`
 - `enableExternalKeying`
 
-When `previewEnabled` is true, the preview window runs on `PreviewWindowThread`. It paints BGRA8 system-memory frames with Win32/GDI after render readback has already completed, so it does not bind GL and does not consume frames from DeckLink output.
+When `previewEnabled` is true, the preview window runs on `PreviewWindowThread`. It paints BGRA8 system-memory frames with Win32/GDI after render readback has already completed, so it does not bind GL and does not consume frames from DeckLink output. `previewFps` controls the preview repaint cadence; the default is 60 fps and `config/runtime-host.json` tracks the shipped 59.94 output cadence.
 
 The loaded config is treated as a read-only startup snapshot. Subsystems that need config should receive this snapshot or a narrowed config struct from app orchestration; they should not reload files independently.
 

src/preview/PreviewConfig.h

@@ -4,7 +4,7 @@
 
 namespace RenderCadenceCompositor
 {
-constexpr double kDefaultPreviewFps = 30.0;
+constexpr double kDefaultPreviewFps = 60.0;
 constexpr double kMinimumPreviewFps = 1.0;
 
 struct PreviewWindowConfig

src/preview/PreviewWindowThread.cpp

@@ -4,6 +4,7 @@
 #include "../logging/Logger.h"
 
 #include <algorithm>
+#include <cstring>
 
 namespace RenderCadenceCompositor
 {
@@ -210,28 +211,48 @@ void PreviewWindowThread::Paint(HWND window)
 		frame.height > 0;
 	if (canPaintFrame)
 	{
-		BITMAPINFO bitmapInfo = {};
-		bitmapInfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
-		bitmapInfo.bmiHeader.biWidth = static_cast<LONG>(frame.width);
-		bitmapInfo.bmiHeader.biHeight = -static_cast<LONG>(frame.height);
-		bitmapInfo.bmiHeader.biPlanes = 1;
-		bitmapInfo.bmiHeader.biBitCount = 32;
-		bitmapInfo.bmiHeader.biCompression = BI_RGB;
+		if (CopyPreviewOrientedBgra8Frame(frame))
+		{
+			const int previousStretchMode = SetStretchBltMode(dc, HALFTONE);
+			POINT previousBrushOrigin = {};
+			SetBrushOrgEx(dc, 0, 0, &previousBrushOrigin);
 
-		StretchDIBits(
-			dc,
-			0,
-			0,
-			clientWidth,
-			clientHeight,
-			0,
-			0,
-			static_cast<int>(frame.width),
-			static_cast<int>(frame.height),
-			frame.bytes,
-			&bitmapInfo,
-			DIB_RGB_COLORS,
-			SRCCOPY);
+			BITMAPINFO bitmapInfo = {};
+			bitmapInfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
+			bitmapInfo.bmiHeader.biWidth = static_cast<LONG>(frame.width);
+			bitmapInfo.bmiHeader.biHeight = -static_cast<LONG>(frame.height);
+			bitmapInfo.bmiHeader.biPlanes = 1;
+			bitmapInfo.bmiHeader.biBitCount = 32;
+			bitmapInfo.bmiHeader.biCompression = BI_RGB;
+
+			StretchDIBits(
+				dc,
+				0,
+				0,
+				clientWidth,
+				clientHeight,
+				0,
+				0,
+				static_cast<int>(frame.width),
+				static_cast<int>(frame.height),
+				mPaintPixels.data(),
+				&bitmapInfo,
+				DIB_RGB_COLORS,
+				SRCCOPY);
+
+			if (previousStretchMode != 0)
+				SetStretchBltMode(dc, previousStretchMode);
+			SetBrushOrgEx(dc, previousBrushOrigin.x, previousBrushOrigin.y, nullptr);
+		}
+		else
+		{
+			if (!mLoggedPaintCopyFailure)
+			{
+				TryLog(LogLevel::Warning, "preview", "Preview frame could not be copied for mirrored presentation.");
+				mLoggedPaintCopyFailure = true;
+			}
+			FillRect(dc, &client, reinterpret_cast<HBRUSH>(GetStockObject(BLACK_BRUSH)));
+		}
 	}
 	else
 	{
@@ -243,4 +264,34 @@ void PreviewWindowThread::Paint(HWND window)
 
 	EndPaint(window, &paint);
 }
+
+bool PreviewWindowThread::CopyPreviewOrientedBgra8Frame(const SystemFrame& frame)
+{
+	constexpr std::size_t kBgraBytesPerPixel = 4;
+	if (frame.bytes == nullptr || frame.width == 0 || frame.height == 0 || frame.rowBytes <= 0)
+		return false;
+
+	const std::size_t width = static_cast<std::size_t>(frame.width);
+	const std::size_t height = static_cast<std::size_t>(frame.height);
+	const std::size_t sourceRowBytes = static_cast<std::size_t>(frame.rowBytes);
+	const std::size_t destinationRowBytes = width * kBgraBytesPerPixel;
+	if (sourceRowBytes < destinationRowBytes)
+		return false;
+
+	mPaintPixels.resize(destinationRowBytes * height);
+	const unsigned char* sourceBytes = static_cast<const unsigned char*>(frame.bytes);
+	for (std::size_t y = 0; y < height; ++y)
+	{
+		const unsigned char* sourceRow = sourceBytes + (height - 1u - y) * sourceRowBytes;
+		unsigned char* destinationRow = mPaintPixels.data() + y * destinationRowBytes;
+		for (std::size_t x = 0; x < width; ++x)
+		{
+			const unsigned char* sourcePixel = sourceRow + x * kBgraBytesPerPixel;
+			unsigned char* destinationPixel = destinationRow + x * kBgraBytesPerPixel;
+			std::memcpy(destinationPixel, sourcePixel, kBgraBytesPerPixel);
+		}
+	}
+
+	return true;
+}
 }

src/preview/PreviewWindowThread.h

@@ -6,6 +6,7 @@
 
 #include <atomic>
 #include <thread>
+#include <vector>
 
 #ifndef NOMINMAX
 #define NOMINMAX
@@ -35,9 +36,12 @@ private:
 	void ThreadMain();
 	bool CreatePreviewWindow(std::string& error);
 	void Paint(HWND window);
+	bool CopyPreviewOrientedBgra8Frame(const SystemFrame& frame);
 
 	SystemFrameExchange* mExchange = nullptr;
 	PreviewWindowConfig mConfig;
+	std::vector<unsigned char> mPaintPixels;
+	bool mLoggedPaintCopyFailure = false;
 	std::thread mThread;
 	std::atomic<bool> mStopRequested{ false };
 	std::atomic<bool> mRunning{ false };

tests/RenderCadenceCompositorAppConfigProviderTests.cpp

@@ -99,7 +99,7 @@ void TestPreviewDefaultsAreOptIn()
 
 	const AppConfig config = DefaultAppConfig();
 	Expect(!config.previewEnabled, "preview is disabled by default");
-	Expect(config.previewFps == 30.0, "preview fps default is 30");
+	Expect(config.previewFps == 60.0, "preview fps default is 60");
 }
 
 void TestHelpers()

tests/RenderCadenceCompositorPreviewConfigTests.cpp

@@ -19,6 +19,7 @@ void TestTimerIntervalUsesConfiguredFps()
 {
 	Expect(RenderCadenceCompositor::PreviewTimerIntervalMilliseconds(25.0) == 40, "25 fps maps to 40 ms");
 	Expect(RenderCadenceCompositor::PreviewTimerIntervalMilliseconds(50.0) == 20, "50 fps maps to 20 ms");
+	Expect(RenderCadenceCompositor::PreviewTimerIntervalMilliseconds(59.94) == 16, "59.94 fps maps to 16 ms");
 }
 
 void TestInvalidFpsUsesDefault()