From Test-Scratch-Wiki
A backdrop is one out of possibly many frames, or backgrounds, of the Stage. It is located in the backdrops library. The Stage can change its look to any of its backdrops. They can be named, edited, created, and deleted, but the Stage must always have at least one backdrop; otherwise, the Stage would not have an image to resemble.
Blocks
Scratch 2.0 has the following 7 blocks related to backdrops:
- Switch Backdrop to () (Looks)
- Switch Backdrop to () and Wait (Looks, Stage only)
- Next Backdrop (Looks, Stage only)
- Backdrop Name () (Looks)
- Backdrop # () (Looks, Stage only)
- When Backdrop Switches to () (Events)
Editing
Backdrops are edited in the same way as costumes. They are found in the backdrops tab in the Stage. Backdrops can also be uploaded as an image file.
Events
Backdrops work similar to broadcasts.
When a backdrop is changed, it sends an event picked up by the When Backdrop Switches to () hat block. As with broadcasts, backdrops be started from any sprite, and can also have their script wait until the backdrop finishes, by using the Switch Backdrop to () and Wait block.
History
Prior to Scratch 2.0, backdrops were called "backgrounds" and had no events. At one point development, they were called "scenes".
Prior to Scratch 2.0, many Scratchers paired switching backgrounds with a broadcast. This is a major reason for why they now have built-in events.
There were originally blocks planned for scrolling the backdrop in Scratch 2.0. They were removed before release, and some users have suggested bringing them back.
