The backing scale factor.
- macOS 10.7+
The value of this property is
2 for high-resolution scaled display modes, and
1 for all other cases.
There are some scenarios where an application that is resolution-aware may want to reason on its own about the display environment it is running in.
It is important to note that the value of this property does not represent anything concrete, such as pixel density or physical size, because it can vary based on the configured display mode. For example, the display may be in a mirrored configuration that is still high-resolution scaled, resulting in pixel geometry that may not match the native resolution of the display device.