"Slider" with relative motion? What is this called?

Question

I'm looking for control that allows relative motion.

This isn't what I'm using it for, but you could consider it in the context of a volume control.

My requirements:

• There is a range of acceptable values.
• The user is currently at a specific value.
• The user can move up or down from their current value, but doesn't have visual information about where they are in the range (except perhaps if they're very close to one of the ends).
• The user can control the speed with which they move up/down the range (scrubbing speed).

I have two mental models for this. The first is sort of a slider, but the position of the slider essentially controls the speed of movement, not the absolute value. So pushing the slider all the way up lets the user scroll through very quickly and it snaps back to zero when the user lets go. The second model is that of a wheel protruding from the screen, sort of like a mouse scroll wheel, where the user "rolls" the wheel up and down to get to the desired value.

• Is there a name for this type of control? I've had zero luck searching for it.

• Are there other models that I should consider? Are either of the above clearly more intuitive, useful, etc. than the other?

• Are there implementations of this type of control that I can take a look at? My development will be in Qt for iOS (long story), but any sort of implementation would be a helpful reference.

Answer 1

The basic functionality sounds to me like what would be in the physical world called a jog dial.

There are two basic types of wheels. One type has no stops and can be spun the entire way around, because it is a relative rotary encoder. This type depends on tracking the actual motion of the dial: the faster it spins forward or back, the faster it fast-forwards or rewinds. Once the dial stops moving, the media continues playing or remains paused at that point. Another type has stops on either side, and often has three or so speeds which depend on how far it is turned. Once the wheel is released, it springs back to the middle position and the media pauses or begins playing again.

Answer 2

In the physical world, one term that could applicable is potentiometer.

It's typically a knob or slider and the further you turn it, the the higher or lower the resistance within.

Note that these are difficult to implement in a virtual UI. Knobs and sliders are great physical objects to interact with*. They can be a real pain to interact with via a mouse, though. Touch devices have narrowed that gap, though, so it's not quite as bad on a touch screen.

(* In fact, I'd argue that we've taken a step backwards when a lot of physical interfaces are now heavily button-based as they have borrowed heavily from virtual UI. They have eschewed the traditional knob which is a real shame, IMHO.)