I want to programmatically set a wallpaper. Here's the only solution I've found so far:
SystemParametersInfoW(SPI_SETDESKWALLPAPER, 1, (void*)wallpaperImageFilePath.utf16(), SPIF_UPDATEINIFILE | SPIF_SENDCHANGE);
My question is: how to tell Windows I want the wallpaper image centered (not resized)? The solution above always sets the image in stretch mode. According to MSDN, there are no flags to accompany SPI_SETDESKWALLPAPER.
As of Windows 8 there is now a published interface for setting the desktop background. Specifically the IDesktopBackground::SetWallpaper method. MSDN Documentation
The interface also has several methods for getting and setting the configuration of the slideshow, and obtaining the required monitor device paths.
There is no API function for setting the wallpaper orientation. You have to go to the Registry directly instead, specifically the "WallpaperStyle" and "TileWallpaper" values of the HKEY_CURRENT_USER\Control Panel\Desktop key. See this article for an example:
