For awhile now (including in Ubuntu 10.10 and 11.04), I've experienced an issue with scroll events initiated on my Touchpad. Steps to reproduce are:
1) Open Firefox
2) Start a vertical scroll event on Touchpad (two-finger scroll, in my case)
3) Quickly hit ctrl
The results are that Firefox will start zooming in or zooming out the page. I also experience this if I start a scroll event and quickly switch to a different workspace — where my Terminal will start scrolling up or down. I would expect that the scroll event would die as soon a meta key is hit.
I'm on a Thinkpad W510 on Ubuntu 11.04 using Unity. Here's all the info I can find on my Touchpad:
[ 10.808053] Synaptics Touchpad, model: 1, fw: 7.2, id: 0x1c0b1, caps: 0xd047b3/0xb40000/0xa0000
[ 10.863551] input: SynPS/2 Synaptics TouchPad as /devices/platform/i8042/serio1/input/input7
Best Answer
Mouse events and keyboard events are independent. In addition, the mouse wheel triggers multiple events, not a single event with a range. You can think of this like a physical mousewheel that has click stops. Each stop is a single event. This is why a keyboard key does not cancel a mouse event and why continuing to scroll on your trackpad fires multiple events.