GIMP used to have something similar, where the input boxes also contain two sliders: sliding on the top half would change the value around its current point, allowing for fine tuning, while clicking on the bottom half would set it immediately to that absolute value, so click in the middle = set it to 50% of the max. [1] has screenshots if I'm not making sense.
It was a bit confusing and seems to be gone, they now use ctrl/shift modifiers instead of separating the area, which is arguably less awkward but also way less discoverable.
Not to get all Don Norman on the author here, but he really means “signifier” almost everywhere he uses “affordance” — he’s talking about the visibility of these sliders’ use, not what they actually allow (or, “afford”).
The volume icon on the Tesla touch screens has the same functionality.
Curiously, it’s at the far bottom right of the screen, such that it’s easy to use the majority of the screen to the left to lower the volume, while increasing the volume is difficult due to the limited screen real wastage to the right. No doubt this was placed here for the passenger of the vehicle to use, but the result that it’s safer to lower the volume quickly than increase it quickly is interesting to me.
Though, I suppose it would have the opposite effect when the passenger is on the left side of the vehicle.
I absolutely loved the seek bars in iOS video player back then (didn't use iOS in a long time).
The video seek bar works as a normal seek bar with left/right dragging, but the seek rate can be slowed down (finer seek) by dragging the finger up, and then moving left/right.
I have yet to see good video seek features in Android.
I don't know if Unity does it but I think I remember Adobe and 3D programs like Maya and 3DS Max also have this "hidden slider" feature which you can also control the increments with a combination of the shift or ctrl key (don't remember which one)
The volume and brightness sliders in the control center on iOS and iPadOS also do the slide anywhere thing.
I found it reasonably discoverable.
At first I assumed I had to touch the boundary between the light and dark part of the slider, but eventually I missed and noticed it still slid. I then experimented to see how close I had to get, and found that anywhere in the control would do and once sliding I did not need to stay inside.
One of the really hidden ones in iOS is press-and-hold the on-screen spacebar to move the text cursor around. I found that one entirely by accident, and it’s made text entry a lot less painful.
Interesting, I’ve never consciously thought about where I’m touching to start the drag, I guess it has ”just worked” wherever I have put my finger. The control does not have a ”physical” slider knob so I think it’s fairly intuitive to expect that you don’t have to be particularly precise (like in touch interfaces in general!)
The not needing to stay inside is true of almost all draggable controls on iOS btw. And you can combine that with multitouch. In a music application you might have 4 or 5 parameters under your fingers, nowhere near the original controls which are small and close together. Seems to work everywhere.
