C++ Windows wallpaper change: WinAPI and COM

Programmatically Switch Desktop Backgrounds and Colors in C++ on Windows

This C++ program for Windows toggles the desktop background between images and a solid color. It runs without a visible console window. In debug mode, the window shows for troubleshooting; in release and test builds, it's hidden.

Two ways to hide the console:

• Programmatic hiding using GetConsoleWindow() and ShowWindow(hWnd, SW_HIDE). The window flashes briefly before hiding.

• Linker directives (recommended approach):

#ifndef _DEBUG
#pragma comment(linker, "/subsystem:windows")
#pragma comment(linker, "/SUBSYSTEM:windows /ENTRY:mainCRTStartup")
#endif

The first directive builds it as a GUI app with WinMain() entry point. The second keeps main() but skips console creation. No flashing.

Build Configurations

Three Visual Studio configurations: Debug, Release, TEST (inherits from Release).

TEST adds the _TEST preprocessor definition in project properties (C/C++ → Preprocessor).

• TEST: Images in the exe folder as 0.jpg...4.jpg. Run: ChangeDesktopColor.exe X (X=0-4).
• Release: Uses full file paths, regardless of exe location.

For TEST debugging in Debug, uncomment #define _TEST.

Get exe path (key for TEST):

wchar_t pathTmp[MAX_PATH] = { L'\0' };
GetModuleFileName(NULL, pathTmp, MAX_PATH);
std::filesystem::path dir = ((std::filesystem::path)pathTmp).parent_path();

argv[0] is empty when launched from Explorer, so use GetModuleFileName.

Select file by argument:

#ifdef _TEST
    switch (*argv[1]) {
    case '0': filePath = dir.wstring() + L"\\0.jpg"; fileName = L"0.jpg"; break;
    // ... similar for 1-4
    default: filePath = dir.wstring() + L"\\4.jpg"; fileName = L"4.jpg";
    }
#else
    switch (*argv[1]) {
    case '0': filePath = L"C:\\folder\\subfolder\\filename0.jpg"; fileName = L"filename0.jpg"; break;
    // ...
    }
#endif

Check Current Wallpaper

Get current background:

wchar_t wallFile[MAX_PATH] = { L'\0' };
SystemParametersInfo(SPI_GETDESKWALLPAPER, MAX_PATH, wallFile, 0);
wchar_t* ptr = wcsstr(wallFile, fileName.c_str());

• If ptr == NULL: solid color or different file.
• wallFile holds the filename or is empty for solid color.

Set Wallpaper or Color

Toggle logic:

if (!ptr && std::filesystem::exists(filePath)) {
    BOOL result = SystemParametersInfoW(SPI_SETDESKWALLPAPER, 0, (void*)filePath.c_str(), 
                                        SPIF_UPDATEINIFILE | SPIF_SENDWININICHANGE);
} else {
    COLORREF blackColor = RGB(0, 0, 0);
#ifdef MyCOM
    HRESULT hr = ChangeDesktopBackgroundColor(blackColor);
    if (SUCCEEDED(hr)) {
        SystemParametersInfo(SPI_SETDESKWALLPAPER, 0, NULL, SPIF_SENDWININICHANGE);
    }
#else
    if (SetDesktopSolidColor(blackColor)) {
        SystemParametersInfo(SPI_SETDESKWALLPAPER, 0, NULL, SPIF_SENDWININICHANGE);
    }
#endif
}

Choose API via #define MyCOM:

• WinAPI (SetDesktopSolidColor): primary method.
• COM (ChangeDesktopBackgroundColor): alternative.

SPIF_SENDWININICHANGE broadcasts the update to all windows.

TEST run examples:

• ChangeDesktopColor.exe 0 → 0.jpg
• ChangeDesktopColor.exe 999 → 4.jpg (default)
• ChangeDesktopColor.exe 1 2 → 0.jpg (first argument)

Practical Uses

Great for cycling backgrounds: image → black → image → ...

Use wallpapers as cheat sheets: 0.jpg shows key combos for Razer NAGA X (12+12 buttons with modifier). Quick macro access without losing focus.

Key takeaways:

• Linker hiding beats programmatic—no flash.
• _TEST simplifies dev with local 0.jpg-4.jpg files.
• wcsstr check distinguishes file from solid color.
• SPIF_UPDATEINIFILE saves to registry.
• Command-line arg picks wallpaper (0-4).

— Editorial Team