Windows: Dark mode improvement; the context menu of the game's window…

… titlebar now also honors the system's dark mode setting. However, we are using undocumented APIs for this, so there are no guarantees that those APIs will remain unchanged in the future. If needed, the macro USE_UNDOCUMENTED_DARKMODE_API can be set to 0 to disable the feature.

src/SDL/MyOpenGLView.m

@@ -52,9 +52,28 @@
 #include <ctype.h>
 
 #if OOLITE_WINDOWS
+#ifndef DWMWA_USE_IMMERSIVE_DARK_MODE
 #define DWMWA_USE_IMMERSIVE_DARK_MODE	20
+#endif
 HRESULT WINAPI DwmSetWindowAttribute (HWND hwnd, DWORD dwAttribute, LPCVOID pvAttribute, DWORD cbAttribute);
+
+#define USE_UNDOCUMENTED_DARKMODE_API	1
+
+#if USE_UNDOCUMENTED_DARKMODE_API
+#ifndef LOAD_LIBRARY_SEARCH_SYSTEM32
+#define LOAD_LIBRARY_SEARCH_SYSTEM32	0x00000800
 #endif
+typedef DWORD(WINAPI* pfnSetPreferredAppMode)(DWORD appMode);
+enum PreferredAppMode
+{
+    Default,
+    AllowDark,
+    ForceDark,
+    ForceLight,
+    Max
+};
+#endif
+#endif //OOLITE_WINDOWS
 
 @interface MyOpenGLView (OOPrivate)
 
@@ -250,7 +269,19 @@ - (id) init
 	}
 
 	atDesktopResolution = YES;
+
+#if USE_UNDOCUMENTED_DARKMODE_API
+	// dark mode stuff - this is mainly for the winodw titlebar's context menu
+	HMODULE hUxTheme = LoadLibraryExW(L"uxtheme.dll", NULL, LOAD_LIBRARY_SEARCH_SYSTEM32);
+	if (hUxTheme)
+	{
+		// hack alert! ordinal 135 is undocumented and could change in a future version of Windows
+		pfnSetPreferredAppMode SetPreferredAppMode = (pfnSetPreferredAppMode)GetProcAddress(hUxTheme, MAKEINTRESOURCEA(135));
+		if (SetPreferredAppMode)  SetPreferredAppMode(AllowDark);
+		FreeLibrary(hUxTheme);
+	}
 #endif
+#endif //OOLITE_WINDOWS
 
 	grabMouseStatus = NO;