Avoid redundant display mode changes

DDrawCompat/CompatDisplayMode.cpp

@@ -10,6 +10,61 @@ namespace
 	HDC g_compatibleDc = nullptr;
 	CompatDisplayMode::DisplayMode g_emulatedDisplayMode = {};
 
+	template <typename CStr, typename DevMode,
+		typename ChangeDisplaySettingsExPtr, typename EnumDisplaySettingsPtr>
+	LONG changeDisplaySettingsEx(
+		ChangeDisplaySettingsExPtr origChangeDisplaySettings,
+		EnumDisplaySettingsPtr origEnumDisplaySettings,
+		CStr lpszDeviceName, DevMode* lpDevMode, HWND hwnd, DWORD dwflags, LPVOID lParam)
+	{
+		DevMode targetDevMode = {};
+		if (lpDevMode)
+		{
+			targetDevMode = *lpDevMode;
+		}
+		else
+		{
+			targetDevMode.dmSize = sizeof(targetDevMode);
+			origEnumDisplaySettings(lpszDeviceName, ENUM_REGISTRY_SETTINGS, &targetDevMode);
+		}
+
+		if (targetDevMode.dmPelsWidth)
+		{
+			DevMode currentDevMode = {};
+			currentDevMode.dmSize = sizeof(currentDevMode);
+			origEnumDisplaySettings(lpszDeviceName, ENUM_CURRENT_SETTINGS, &currentDevMode);
+
+			if (targetDevMode.dmPelsWidth == currentDevMode.dmPelsWidth &&
+				targetDevMode.dmPelsHeight == currentDevMode.dmPelsHeight &&
+				targetDevMode.dmBitsPerPel == currentDevMode.dmBitsPerPel &&
+				targetDevMode.dmDisplayFrequency == currentDevMode.dmDisplayFrequency &&
+				targetDevMode.dmDisplayFlags == currentDevMode.dmDisplayFlags)
+			{
+				HANDLE dwmDxFullScreenTransitionEvent = OpenEventW(
+					EVENT_MODIFY_STATE, FALSE, L"DWM_DX_FULLSCREEN_TRANSITION_EVENT");
+				SetEvent(dwmDxFullScreenTransitionEvent);
+				CloseHandle(dwmDxFullScreenTransitionEvent);
+				return DISP_CHANGE_SUCCESSFUL;
+			}
+		}
+
+		return origChangeDisplaySettings(lpszDeviceName, lpDevMode, hwnd, dwflags, lParam);
+	}
+
+	LONG WINAPI changeDisplaySettingsExA(
+		LPCSTR lpszDeviceName, DEVMODEA* lpDevMode, HWND hwnd, DWORD dwflags, LPVOID lParam)
+	{
+		return changeDisplaySettingsEx(CALL_ORIG_FUNC(ChangeDisplaySettingsExA),
+			CALL_ORIG_FUNC(EnumDisplaySettingsA), lpszDeviceName, lpDevMode, hwnd, dwflags, lParam);
+	}
+
+	LONG WINAPI changeDisplaySettingsExW(
+		LPCWSTR lpszDeviceName, DEVMODEW* lpDevMode, HWND hwnd, DWORD dwflags, LPVOID lParam)
+	{
+		return changeDisplaySettingsEx(CALL_ORIG_FUNC(ChangeDisplaySettingsExW),
+			CALL_ORIG_FUNC(EnumDisplaySettingsW), lpszDeviceName, lpDevMode, hwnd, dwflags, lParam);
+	}
+
 	CompatPtr<IDirectDrawSurface7> createCompatibleSurface()
 	{
 		DDSURFACEDESC2 desc = {};
@@ -151,6 +206,12 @@ namespace CompatDisplayMode
 		return dm;
 	}
 
+	void installHooks()
+	{
+		HOOK_FUNCTION(user32, ChangeDisplaySettingsExA, changeDisplaySettingsExA);
+		HOOK_FUNCTION(user32, ChangeDisplaySettingsExW, changeDisplaySettingsExW);
+	}
+
 	HRESULT restoreDisplayMode(CompatRef<IDirectDraw7> dd)
 	{
 		const HRESULT result = dd->RestoreDisplayMode(&dd);

DDrawCompat/CompatDisplayMode.h

@@ -17,6 +17,8 @@ namespace CompatDisplayMode
 		DWORD flags;
 	};
 
+	void installHooks();
+
 	HBITMAP WINAPI createCompatibleBitmap(HDC hdc, int cx, int cy);
 	HBITMAP WINAPI createDIBitmap(HDC hdc, const BITMAPINFOHEADER* lpbmih, DWORD fdwInit,
 		const void* lpbInit, const BITMAPINFO* lpbmi, UINT fuUsage);

DDrawCompat/DDrawLog.cpp

@@ -14,6 +14,13 @@ namespace
 		empty.dwSize = t.dwSize;
 		return 0 == memcmp(&t, &empty, sizeof(t));
 	}
+
+	template <typename DevMode>
+	std::ostream& streamDevMode(std::ostream& os, const DevMode& dm)
+	{
+		return os << "DM(" << dm.dmPelsWidth << ',' << dm.dmPelsHeight << ',' << dm.dmBitsPerPel <<
+			',' << dm.dmDisplayFrequency << ',' << dm.dmDisplayFlags << ')';
+	}
 }
 
 std::ostream& operator<<(std::ostream& os, const char* str)
@@ -42,6 +49,16 @@ std::ostream& operator<<(std::ostream& os, const WCHAR* wstr)
 	return os << '"' << static_cast<const char*>(str) << '"';
 }
 
+std::ostream& operator<<(std::ostream& os, const DEVMODEA& dm)
+{
+	return streamDevMode(os, dm);
+}
+
+std::ostream& operator<<(std::ostream& os, const DEVMODEW& dm)
+{
+	return streamDevMode(os, dm);
+}
+
 std::ostream& operator<<(std::ostream& os, const RECT& rect)
 {
 	return os << "R(" << rect.left << ',' << rect.top << ',' << rect.right << ',' << rect.bottom << ')';

DDrawCompat/DDrawLog.h

@@ -17,6 +17,8 @@
 std::ostream& operator<<(std::ostream& os, const char* str);
 std::ostream& operator<<(std::ostream& os, const unsigned char* data);
 std::ostream& operator<<(std::ostream& os, const WCHAR* wstr);
+std::ostream& operator<<(std::ostream& os, const DEVMODEA& dm);
+std::ostream& operator<<(std::ostream& os, const DEVMODEW& dm);
 std::ostream& operator<<(std::ostream& os, const RECT& rect);
 std::ostream& operator<<(std::ostream& os, HDC__& dc);
 std::ostream& operator<<(std::ostream& os, HWND__& hwnd);

DDrawCompat/DllMain.cpp

@@ -9,6 +9,7 @@
 #include "CompatDirectDraw.h"
 #include "CompatDirectDrawSurface.h"
 #include "CompatDirectDrawPalette.h"
+#include "CompatDisplayMode.h"
 #include "CompatFontSmoothing.h"
 #include "CompatGdi.h"
 #include "CompatHooks.h"
@@ -199,6 +200,8 @@ BOOL WINAPI DllMain(HINSTANCE hinstDLL, DWORD fdwReason, LPVOID /*lpvReserved*/)
 		SetProcessPriorityBoost(GetCurrentProcess(), disablePriorityBoost);
 		SetProcessAffinityMask(GetCurrentProcess(), 1);
 		SetThemeAppProperties(0);
+
+		CompatDisplayMode::installHooks();
 		CompatFontSmoothing::g_origSystemSettings = CompatFontSmoothing::getSystemSettings();
 		CompatHooks::installHooks();
 		Time::init();