A pushbutton user interface enables a user to preview the effect of activating
a pushbutton of the interface before the pushbutton is activated. The pushbutton
user interface can be implemented so that an input (preview input) to the pushbutton
that does not produce an activation of the pushbutton is sensed and, in response
to the sensed input, a preview is displayed that indicates the effect of activating
the pushbutton. The preview input can be sensed using, for example, a force-sensitive
resistor, potentiometer or strain gauge. The preview display can include, for example,
a visual display, an audio display, a haptic display, or a combination of two or
three such displays. The pushbutton user interface can be implemented so that the
preview input and an activation input (i.e., an input that produces an activation
of the pushbutton) are sensed as a result of an input to the pushbutton along the
same axis or along different (e.g., orthogonal) axes.