Question about MOUSE_WHEEL and ButtonData

NTDEV
1

The MOUSE_WHEEL flag indicates that ButtonData contains mouse wheel data.
WHEEL_DELTA is 120, so if you scroll upwards on time, ButtonData has the value 120.

However, if you constantly scroll upwards, can ButtonData have multiple WHEEL_DELTAs or will there always be one packet each for one WHEEL_DELTA?

I have done some tests and it seems like one packet per WHEEL_DELTA, but can I assume this is always the case (I could save a division)?

I hope my question is clear, thanks.

2

Don’t assume that, no.

Among other things, some more recent MS mice send wheelmouse messages
*smaller* than 120 that Vista knows how to handle.

Also, there are 3rd party pointing devices that send various sizes of
wheel packets.

And if the system spends too much time at a high device IRQL, you can
miss mouse interrupts and the mouse will accumulate up multiple wheel
clicks, even on a standard run-of-the-mill wheelmouse with the normal MS
driver.

xxxxx@hushmail.com wrote:

The MOUSE_WHEEL flag indicates that ButtonData contains mouse wheel data.
WHEEL_DELTA is 120, so if you scroll upwards on time, ButtonData has the value 120.

However, if you constantly scroll upwards, can ButtonData have multiple WHEEL_DELTAs or will there always be one packet each for one WHEEL_DELTA?

I have done some tests and it seems like one packet per WHEEL_DELTA, but can I assume this is always the case (I could save a division)?

I hope my question is clear, thanks.

–
Ray
(If you want to reply to me off list, please remove “spamblock.” from my
email address)

3

Thanks for your reply!

Ray Trent wrote:

Also, there are 3rd party pointing devices that send various sizes of
wheel packets.
Do you know if these sizes are also smaller than 120 or can they be bigger?

4

Yes, as I said in my first reply, they can be smaller than 120 on Vista
with newer MS mice.

See http://msdn2.microsoft.com/en-us/library/ms997498.aspx.

xxxxx@hushmail.com wrote:

Thanks for your reply!

Ray Trent wrote:
> Also, there are 3rd party pointing devices that send various sizes of
> wheel packets.
Do you know if these sizes are also smaller than 120 or can they be bigger?

–
Ray
(If you want to reply to me off list, please remove “spamblock.” from my
email address)