SmoothWheel - Vsync and other issues

If you experience occasional short 'hangs' while scrolling - it is not related to Vsync. These are usually extensions/addons which do something wrong (programming-wise) in the background, and this may prevent the entire window from being responsive. Another possible reason is Firefox updating Live-bookmarks in the background. To verify it, try to continuously drag the the scroll-bar up and down for few seconds. You would probably notice similar issues.

This is unrelated to SmoothWheel but still affects smoothness. Usually you won't notice those hangs during a normal browsing experience, but they are noticeable when scrolling very smoothly. To try and identify possibly fauly addons, disable a different group of them at a time, and observe if the issue still exist. Then, narrow it down to pinpoint specific fauly ones.
  • What is Vsync?
    Vsync is proper timing synchronization between applications drawing to the screen, and the refresh rate of the screen (monitor). When they're properly synchronized, animations look much more solid and smooth. Vsync is especially important for computer games.
  • Why is it related to SmoothWheel?
    SmoothWheel can scroll the screen very fluidly. Lack of Vsync may degrade smoothness and thus provide sub-optimal experience with SmoothWheel. Known visual artifacts: slight wobbliness, less-than-optimal smoothness, etc.
  • So, how do I turn Vsync on?
    You can't. Not directly at least. Since Firefox* is not developed as an animation-intense application, it doesn't offer Vsync support. However, on some cases, Vsync is turned on for your entire desktop. On Aero Glass (Windows 7/Vista default desktop) it's always turned on. If you use Compiz on Linux, you may be able to turn Vsync on for the compositor. Windows XP doesn't provide native desktop Vsync support.
  • What if I have Windows XP?
    On some Windows XP systems, when an application which uses Vsync is running (examples: a 3D game, some video players during playback, etc), Vsync is turned on for the entire desktop. Even having a Flash video running in a browser may turn Vsync on for the desktop. In fact, the solution might be as simple as having any Flash object in any single window/tab of the browser.

    Here's a simple page with a Flash object that you can try.

    This is an ugly hack indeed, but properly turning Vsync on for the desktop on Windows XP largely remains an unsolved issue. Still, it might improve your experience so it's worth trying. If you know of a better way, please leave a comment and I'll update this page accordingly.
* Also applies to Thunderbird/Seamonkey/Songbird/etc.