From f589b1e1fef4e435cbe1c8aa2ec14c60d7cc05be Mon Sep 17 00:00:00 2001
From: Aiden <awils27@hotmail.com>
Date: Wed, 20 May 2026 15:03:02 +1000
Subject: [PATCH] preview window flipped

---
 src/preview/PreviewWindowThread.cpp | 97 +++++++++++++++++++++--------
 src/preview/PreviewWindowThread.h   |  4 ++
 2 files changed, 74 insertions(+), 27 deletions(-)

diff --git a/src/preview/PreviewWindowThread.cpp b/src/preview/PreviewWindowThread.cpp
index d543b01..485187e 100644
--- a/src/preview/PreviewWindowThread.cpp
+++ b/src/preview/PreviewWindowThread.cpp
@@ -4,6 +4,7 @@
 #include "../logging/Logger.h"
 
 #include <algorithm>
+#include <cstring>
 
 namespace RenderCadenceCompositor
 {
@@ -210,36 +211,48 @@ void PreviewWindowThread::Paint(HWND window)
 		frame.height > 0;
 	if (canPaintFrame)
 	{
-		const int previousStretchMode = SetStretchBltMode(dc, HALFTONE);
-		POINT previousBrushOrigin = {};
-		SetBrushOrgEx(dc, 0, 0, &previousBrushOrigin);
+		if (CopyPreviewOrientedBgra8Frame(frame))
+		{
+			const int previousStretchMode = SetStretchBltMode(dc, HALFTONE);
+			POINT previousBrushOrigin = {};
+			SetBrushOrgEx(dc, 0, 0, &previousBrushOrigin);
 
-		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;
+			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),
-			frame.bytes,
-			&bitmapInfo,
-			DIB_RGB_COLORS,
-			SRCCOPY);
+			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);
+			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
 	{
@@ -251,4 +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;
+}
 }
diff --git a/src/preview/PreviewWindowThread.h b/src/preview/PreviewWindowThread.h
index b177ad7..a0f3022 100644
--- a/src/preview/PreviewWindowThread.h
+++ b/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 };