Foldable concepts for UI tests
When working with foldable devices, there are a few concepts and terms that are helpful to know. This information makes it easier to understand what kinds of situations need to be addressed and tested when adding foldable support to apps.
Device types
All foldable devices have a physical fold or hinge, which enables the device display to change dynamically.
Some devices have two distinct screens separated by a physical hinge, like the Surface Duo:
When talking about all kinds of devices, here are some common terms we use:
| Term | Definition |
|---|---|
| Foldable | Most general term, refers to any device that can fold |
| Dual-screen | Type of foldable that has two separate screens |
| Single-screen | Conventional device that has one small non-folding display |
| Large screen | Device with a large display, can include foldables that are completely open |
To read more about these devices and how to enhance your apps, check out these resources:
- Dual-screen device introduction
- Design for foldables
- Get started with large screens
- Learn about foldables
Folding features
When discussing folding features, here are some additional terms we use:
| Term(s) | Definition | API reference |
|---|---|---|
| Display feature | Most general term, refers to any unique display feature on a device | DisplayFeature |
| Folding feature, fold | Type of display feature that enables device to fold | FoldingFeature |
| Hinge | Type of fold that occludes content | FoldingFeature with occlusionType FULL |
To read more about folding features and their properties, check out the Jetpack Window Manager library.
Surface Duo display operations
Because the Surface Duo is a dual-screen device, users can choose which screen(s) an app should fill. To change how an app is displayed, there are several different gestures users can perform.
| Operation | Definition | Example |
|---|---|---|
| Span | Display an app on both screens |  |
| Unspan | Display an app on one screen |  |
| Switch | Change which screen an app is displayed on |  |
| Close | Stop displaying an app |  |
Foldable display states
Although the operations above are specific to the Surface Duo, we sometimes borrow those terms to refer to display states on all foldables.
| State | Definition | Synonyms |
|---|---|---|
| spanned | When an app is displayed on both sides of a folding feature | dual-screen, unfolded, open |
| unspanned | When an app is only displayed on one side of a folding feature or on an outer screen | single-screen, folded, closed |
To read more about foldable display states and postures, check out these resources: