A window shade comprising: a fixed rail, a movable rail, a covering structure arranged between the fixed rail and the movable rail, an electric motor operable to drive displacement of the movable rail relative to the fixed rail, a control interface operable to control operation of the electric motor and including a first, a second and a third button (154A, 154B, 154C), the first button being operable to cause displacement of the movable rail in a first direction, and the second button being operable to cause displacement of the movable rail in a second direction opposite to the first direction, and a motor controller respectively connected with the electric motor and the control interface, characterized in that the motor controller is configured to: record a first position of the movable rail as a first limit position of the movable rail in response to a pressure concurrently applied on the third button and the first button; record a second position of the movable rail as an intermediate limit position of the movable rail in response to a sequence of a first and a second pressing action successively applied on the third button; and record a third position of the movable rail as a second limit position of the movable rail in response to a pressure concurrently applied on the third button and the second button, the intermediate limit position being located between the first and second limit positions. a fixed rail, a movable rail, a covering structure arranged between the fixed rail and the movable rail, an electric motor operable to drive displacement of the movable rail relative to the fixed rail, a control interface operable to control operation of the electric motor and including a first, a second and a third button (154A, 154B, 154C), the first button being operable to cause displacement of the movable rail in a first direction, and the second button being operable to cause displacement of the movable rail in a second direction opposite to the first direction, and a motor controller respectively connected with the electric motor and the control interface, characterized in that the motor controller is configured to: record a first position of the movable rail as a first limit position of the movable rail in response to a pressure concurrently applied on the third button and the first button; record a second position of the movable rail as an intermediate limit position of the movable rail in response to a sequence of a first and a second pressing action successively applied on the third button; and record a third position of the movable rail as a second limit position of the movable rail in response to a pressure concurrently applied on the third button and the second button, the intermediate limit position being located between the first and second limit positions. record a first position of the movable rail as a first limit position of the movable rail in response to a pressure concurrently applied on the third button and the first button; record a second position of the movable rail as an intermediate limit position of the movable rail in response to a sequence of a first and a second pressing action successively applied on the third button; and record a third position of the movable rail as a second limit position of the movable rail in response to a pressure concurrently applied on the third button and the second button, the intermediate limit position being located between the first and second limit positions.