Prefabricated shower units are designed to roll into, accommodating rolling shower chairs designed for the purpose. Prefab units have only a small lip at the edge, rather than the three-inch or larger lip that are common to most stall showers. These units can be used in new construction or replace an existing bathtub. Faucets, shower heads, and handholds are installed on the walls, also tiled. You wheel into the area in a rolling shower chair to wash.
Grab bars are essential, particularly around the shower, toilet, and bidet.
A grab bar needs to be attached to a solid structure in the wall, typically horizontal reinforcement between vertical studs that can be drilled into. Builders are now encouraged to provide support structure in bathroom walls for the eventual addition of grab bars, but it is not yet a standard construction measure. When sufficient structure is not already present, it is sometimes necessary to break into the wall to add the structural backing. I moved into a newly built apartment complex that used the handicapped-adaptable approach. In my smaller, second bathroom they couldn't put a grab bar in the bathtub because they hadn't reinforced the wall.