diff --git a/DDrawCompat/D3dDdi/KernelModeThunks.cpp b/DDrawCompat/D3dDdi/KernelModeThunks.cpp
index fe5bd2c..fec9485 100644
--- a/DDrawCompat/D3dDdi/KernelModeThunks.cpp
+++ b/DDrawCompat/D3dDdi/KernelModeThunks.cpp
@@ -251,25 +251,7 @@ namespace
 
 	void waitForVerticalBlank()
 	{
-		D3DKMT_WAITFORVERTICALBLANKEVENT data = {};
-
-		{
-			Compat::ScopedSrwLockShared lock(g_lastOpenAdapterInfoSrwLock);
-			data.hAdapter = g_lastOpenAdapterInfo.adapter;
-			data.VidPnSourceId = g_lastOpenAdapterInfo.vidPnSourceId;
-		}
-
-		if (!data.hAdapter)
-		{
-			updateGdiAdapterInfo();
-			data.hAdapter = g_gdiAdapterInfo.adapter;
-			data.VidPnSourceId = g_gdiAdapterInfo.vidPnSourceId;
-		}
-
-		if (!data.hAdapter || FAILED(D3DKMTWaitForVerticalBlankEvent(&data)))
-		{
-			Sleep(16);
-		}
+		Sleep(16);
 	}
 }
 
diff --git a/DDrawCompat/Gdi/User32WndProcs.cpp b/DDrawCompat/Gdi/User32WndProcs.cpp
index 236b897..436ccd9 100644
--- a/DDrawCompat/Gdi/User32WndProcs.cpp
+++ b/DDrawCompat/Gdi/User32WndProcs.cpp
@@ -1,5 +1,8 @@
+#include <dwmapi.h>
+
 #include <D3dDdi/ScopedCriticalSection.h>
 #include <Gdi/CompatDc.h>
+#include <Gdi/Region.h>
 #include <Gdi/ScrollBar.h>
 #include <Gdi/ScrollFunctions.h>
 #include <Gdi/TitleBar.h>
@@ -156,8 +159,20 @@ namespace
 			}
 			break;
 
+		case WM_DWMCOMPOSITIONCHANGED:
+		{
+			BOOL isEnabled = FALSE;
+			HRESULT result = DwmIsCompositionEnabled(&isEnabled);
+			LOG_DEBUG << "DwmIsCompositionEnabled: " << Compat::hex(result) << " " << isEnabled;
+			break;
+		}
+
 		case WM_ERASEBKGND:
 		{
+			Gdi::Region updateRegion;
+			GetUpdateRgn(hwnd, updateRegion, FALSE);
+			LOG_DEBUG << "updateRegion: " << static_cast<HRGN>(updateRegion);
+
 			HBRUSH brush = reinterpret_cast<HBRUSH>(GetClassLong(hwnd, GCL_HBRBACKGROUND));
 			if (!brush)
 			{
diff --git a/DDrawCompat/Gdi/Window.cpp b/DDrawCompat/Gdi/Window.cpp
index bd1c184..f860d41 100644
--- a/DDrawCompat/Gdi/Window.cpp
+++ b/DDrawCompat/Gdi/Window.cpp
@@ -100,6 +100,9 @@ namespace
 	void updatePosition(Window& window, const RECT& oldWindowRect, const RECT& oldClientRect,
 		const Gdi::Region& oldVisibleRegion, Gdi::Region& invalidatedRegion)
 	{
+		LOG_FUNC("Window::updatePosition", window.hwnd, oldWindowRect, oldClientRect,
+			static_cast<HRGN>(oldVisibleRegion), static_cast<HRGN>(invalidatedRegion));
+
 		const bool isClientOriginChanged =
 			window.clientRect.left - window.windowRect.left != oldClientRect.left - oldWindowRect.left ||
 			window.clientRect.top - window.windowRect.top != oldClientRect.top - oldWindowRect.top;
@@ -155,6 +158,8 @@ namespace
 				GetUpdateRgn(window.hwnd, updateRegion, FALSE);
 				updateRegion.offset(window.clientRect.left, window.clientRect.top);
 				preservedRegion -= updateRegion;
+				LOG_DEBUG << "updateRegion: " << static_cast<HRGN>(updateRegion);
+				LOG_DEBUG << "preservedRegion: " << static_cast<HRGN>(preservedRegion);
 			}
 
 			bool isCopied = false;
@@ -170,14 +175,18 @@ namespace
 			if (isCopied)
 			{
 				invalidatedRegion |= preservedRegion;
+				LOG_DEBUG << "isCopied invalidatedRegion: " << static_cast<HRGN>(invalidatedRegion);
 			}
 		}
 
+		LOG_DEBUG << "window.visibleRegion: " << static_cast<HRGN>(window.visibleRegion);
+		LOG_DEBUG << "old window.invalidatedRegion: " << static_cast<HRGN>(window.invalidatedRegion);
 		window.invalidatedRegion = window.visibleRegion - preservedRegion;
 		if (!window.invalidatedRegion.isEmpty())
 		{
 			window.invalidatedRegion.offset(-window.clientRect.left, -window.clientRect.top);
 		}
+		LOG_DEBUG << "new window.invalidatedRegion: " << static_cast<HRGN>(window.invalidatedRegion);
 	}
 
 	BOOL CALLBACK updateWindow(HWND hwnd, LPARAM lParam)
@@ -375,11 +384,18 @@ namespace Gdi
 				}
 
 				isInvalidated = !it->second.invalidatedRegion.isEmpty();
+				LOG_DEBUG << "isInvalidated: " << isInvalidated << " " << static_cast<HRGN>(it->second.invalidatedRegion);
+				Gdi::Region updateRegion;
+				GetUpdateRgn(hwnd, updateRegion, FALSE);
+				LOG_DEBUG << "updateRegion: " << static_cast<HRGN>(updateRegion);
+
 				if (isInvalidated)
 				{
 					RedrawWindow(hwnd, nullptr, it->second.invalidatedRegion,
 						RDW_INVALIDATE | RDW_ERASE | RDW_FRAME | RDW_ALLCHILDREN);
-					it->second.invalidatedRegion = nullptr;
+					it->second.invalidatedRegion.clear();
+					GetUpdateRgn(hwnd, updateRegion, FALSE);
+					LOG_DEBUG << "updated updateRegion: " << static_cast<HRGN>(updateRegion);
 				}
 			}