Author Topic: MouseWheel Delta Value (Read 4668 times)

triangle · « **on:** January 15, 2010, 12:43:30 am »

I have found that the mouse wheel is extremely unresponsive when using the delta provided by WindowImplWin32::ProcessEvent.

Removing the division by 120 in that function solves the problem and gives me smooth scrolling movement.

I am using a Microsoft Wireless Intellimouse Explorer 2.0, which I would presume is quite standard in operation.

There must be a reason for that seemingly arbitary value of 120, maybe a hardware issue?

Is anyone else using mouse wheel events to achieve smooth scrolling? If so, did you also have to change the delta value?

Laurent · « **Reply #1 on:** January 15, 2010, 08:35:20 am »

The MSDN clearly states that the delta value given by the OS is a multiple of 120, that's why I divide by this value, so that one wheel step == 1 and not 120.

It also says that 120 was chosen to allow vendors to build "finer-resolution wheels (a freely-rotating wheel with no notches)", but 120 is still the base unit, ie. when delta is 120 you scrolled exactly one single step.

I don't think that the Microsoft Wireless Intellimouse Explorer 2.0 has this kind of wheel, does it?

richardwb · « **Reply #2 on:** January 15, 2010, 10:55:34 am »

That particular mouse does have a smooth scrolling wheel.

If this helps any, I've found that in my own Win32 code (not SFML related) I had to accumulate the delta value (in the high word of wparam) and check if it added up to WHEEL_DELTA or more.

http://msdn.microsoft.com/en-us/library/ms645617%28VS.85%29.aspx

Quote

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.

Laurent · « **Reply #3 on:** January 15, 2010, 11:03:46 am »

Ah, true. And this reminds me that there is the same problem for Mac OS X users and the Apple mouse.

I'll fix this as soon as I can.

Thanks for your feedback

triangle · « **Reply #4 on:** January 15, 2010, 11:51:59 am »

Quote from: "Laurent"

The MSDN clearly states that the delta value given by the OS is a multiple of 120, that's why I divide by this value, so that one wheel step == 1 and not 120.

It actually says 'The high-order word indicates the distance the wheel is rotated, expressed in multiples or divisions of WHEEL_DELTA, which is 120', so we miss any events that are divisions of 120...