I am refactoring an old program that I wrote which will set the user's wallpaper to NASA's Astronomy Picture of the Day, each day. I'm programming one part that will let the user specify which style of wallpaper they want (Tile, Center, Stretch, etc), depending on whether the image is larger or smaller than their monitor's resolution. I did a bit of research, and found this program, which claims that the "Fill" and "Fit" wallpaper styles were introduced in Windows 7. I've added the appropriate code to make sure they're running Windows 7 or greater if they choose that style. I noticed that my Windows 10 machine has a "Span" style, which isn't listed in the aforementioned program. This makes me think it was introduced after Windows 7, but I'm not sure if it was introduced in 8, 8.1 or 10. I need to know which of these introduced the Span style, so I can make sure the user has the appropriate version of Windows before I change their wallpaper style to Span, should they select that. Which version was it introduced in?
It was introduced in Windows 8.
However, the option will only appear there if all monitors are the same size or if Let me choose one scaling level for all my displays is checked in the Display screen in the desktop Control Panel. It seems to appear even when there's only one monitor; props to Journeyman Geek for testing.
You can simulate this effect in Windows 7 and below by creating a single, large bitmap that is the sum of the width of all connected screens and choosing "tile" as the layout style.
The upper-leftmost pixel on display 1 is the origin, and as long as the bitmap is exactly the size of the screens, it will be "tiled" only once, causing a single image to span across all displays. This trick worked even if the screens were all of different resolutions.
There is a program called UltraMon that automates this, but the software is not free. It's very useful on Win7 and below, but Microsoft has added features starting w/ Windows 8 that has made many of its features irrelevant.