Seasickness Post Mortem

Here's a short follow-up up on our earlier "You Be The Detective", where we explained a surprisingly widespread phenomenon which, while described in many different ways by users who experience it, nearly always involves the word "seasick."

We correctly explained the phenomenon as caused by accidentally turning on the system's built-in Zoom feature, but we neglected to clarify how the Zoom feature was accidentally turned on. We said:

...these users must accidentally have pressed the keyboard combination (Command-Option-Equal, by default) that zooms in.

Uh, no. As a very astute reader has pointed out to us, there is another way this can happen. In System Preferences, go to Keyboard & Mouse and look at the Mouse pane (or Trackpad if that's what you've got). At the bottom there's a checkbox: "Zoom using scroll wheel while holding Control." (The use of the Control modifer is configurable.)

This feature appeared for the first time in the 10.4.8 update - without warning, and switched on by default. Holding Control and brushing the scroll wheel, or performing an equivalent gesture (such as touching the trackpad with two finger on a recent portable), is very easy to do accidentally, and is sufficient to trigger the phenomenon. That explains why there has been a recent spate of seasickness among users.

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