Custom Partitioning
This view shows each detected drive and its partitions in a Granite.StorageBar-type widget. Selecting a partition displays a popover with a "Use partition" switch. Turning on the switch reveals a "Format" switch, plus "Use as" and "Filesystem" dropdowns.
In the action area, the "Erase and Install" primary action is marked as destructive, and is only enabled when a valid partitioning scheme is selected.
A "Modify Partitions…" is in the incidental position, and opens a partition editor (currently GParted) when selected. When the partition editor is closed, this view reloads with the changes.
If the user wants to use an existing encrypted LUKS partition, first they need to decrypt it. They must provide the password, and can optionally provide a device name (data will be chosen by default). We use a popover for this to clearly point to the partition we're decrypting, but we use a dialog-inspired layout to provide enough information and a familiar authentication UI.