Set the current display length for the given side kind.
The size needs to be in device-independent pixels, see the AppStream documentation for more information: https://www.freedesktop.org/software/appstream/docs/chap-Metadata.html#tag-relations-display_length
Setting a value explicitly will disable any automatic detection of the display size.
| this |
a SystemInfo instance. |
| side |
the DisplaySideKind to select. |
| value_dip |
the length value in device-independt pixels. |