Rewrite WIN_GetSystemTheme() so we don't need to bump Windows SDK versions

src/core/windows/SDL_windows.h

@@ -41,7 +41,7 @@
 #elif defined(HAVE_SHELLSCALINGAPI_H)
 #define _WIN32_WINNT 0x603 /* For DPI support */
 #else
-#define _WIN32_WINNT 0x502 /* Need 0x410 for AlphaBlend() and 0x500 for EnumDisplayDevices(), 0x501 for raw input, 0x502 for RegGetValue() */
+#define _WIN32_WINNT 0x501 /* Need 0x410 for AlphaBlend() and 0x500 for EnumDisplayDevices(), 0x501 for raw input */
 #endif
 #define WINVER _WIN32_WINNT
 

src/video/windows/SDL_windowsvideo.c

@@ -680,21 +680,22 @@ SDL_bool SDL_DXGIGetOutputInfo(SDL_DisplayID displayID, int *adapterIndex, int *
 
 SDL_SystemTheme WIN_GetSystemTheme(void)
 {
-    DWORD type;
-    DWORD value;
-    DWORD count = sizeof(value);
-    LSTATUS status;
+    SDL_SystemTheme theme = SDL_SYSTEM_THEME_LIGHT;
+    HKEY hKey;
+    DWORD dwType = REG_DWORD;
+    DWORD value = ~0;
+    DWORD length = sizeof(value);
 
     /* Technically this isn't the system theme, but it's the preference for applications */
-    status = RegGetValue(HKEY_CURRENT_USER,
-                         TEXT("Software\\Microsoft\\Windows\\CurrentVersion\\Themes\\Personalize"),
-                         TEXT("AppsUseLightTheme"),
-                         RRF_RT_REG_DWORD, &type, &value, &count);
-    if (status == ERROR_SUCCESS && type == REG_DWORD && value == 0) {
-        return SDL_SYSTEM_THEME_DARK;
-    } else {
-        return SDL_SYSTEM_THEME_LIGHT;
+    if (RegOpenKeyExW(HKEY_CURRENT_USER, L"Software\\Microsoft\\Windows\\CurrentVersion\\Themes\\Personalize", 0, KEY_READ, &hKey) == ERROR_SUCCESS) {
+        if (RegQueryValueExW(hKey, L"AppsUseLightTheme", 0, &dwType, (LPBYTE)&value, &length) == ERROR_SUCCESS) {
+            if (value == 0) {
+                theme = SDL_SYSTEM_THEME_DARK;
+            }
+        }
+        RegCloseKey(hKey);
     }
+    return theme;
 }
 
 SDL_bool WIN_IsPerMonitorV2DPIAware(_THIS)