Die Doku ist doch eigentlich sehr eindeutig:
Zitat:
The wheel rotation will be a multiple of WHEEL_DELTA, which is set at 120. This is the threshold for action to be taken, and one such action (for example, scrolling one increment) should occur for each delta.
The delta was set to 120 to allow Microsoft or other vendors to build finer-resolution wheels (a freely-rotating wheel with no notches) to send more messages per rotation, but with a smaller value in each message. To use this feature, you can either add the incoming delta values until WHEEL_DELTA is reached (so for a delta-rotation you get the same response), or scroll partial lines in response to the more frequent messages. You can also choose your scroll granularity and accumulate deltas until it is reached.
Quelle
Zitat:
Currently, a value of 120 is the standard for one detent. If higher resolution mice are introduced, the definition of WHEEL_DELTA might become smaller. Most applications should check for a positive or negative value rather than an aggregate total.
Quelle (.net)
Bonus:
Zitat:
The value of 120 can be evenly divided by 2, 3, 4 or 5. This gives a mouse manufacturer more options in dividing up the current coarser clicks into an even number of higher resolution clicks.
Quelle
Interessieren würde mich jetzt aber trotzdem, was z.B. eine Maus mit frei drehendem
Rad von sich gibt. Oder ein gutes Notebook-Touchpad. Die können ja mittlerweile wirklich super fein scrollen und viele Anwendungen (z.B. Browser) unterstützten das auch.