Betalogue

I am afraid I have to correct what I wrote yesterday about the recently released Mac OS X 10.5.2 update.

While it is still a very good release overall, there is one problem in Mac OS X 10.5 that the update does not seem to have entirely fixed.

The problem is a bit hard to describe, but it has to do with the ability of the system to track the user’s mouse movements. Since I have a fair amount of screen real estate (30″+ 23″ in an extended desktop setup), I often have to move windows between positions that are quite far apart.

I use USB Overdrive to fine-tune the ability of the system to track my mouse movements, but even with USB Overdrive, and even with the latest Mac OS X 10.5.2 update, I still occasionally experience mouse tracking problems.

Typically, the problem occurs when I try to move a window from one screen to the other in a single big and quick mouse movement. Normally, with my settings and with the amplitude of my hand’s movement, a single mouse movement should be more than enough to take the window from one screen to the other.

But occasionally, even with a big and quick mouse movement, Mac OS X interrupts the process of moving the window from one screen to the other. It looks as if I have hit an invisible wall and the window refuses to go farther to the right (or to the left) until I lift the mouse and try again.

It looks like the source of the problem is something that causes the OS to lose track of the big mouse movement to the right (or left) right in the middle of it.

I have no idea what it could be, but I am still able to reproduce the problem by simply trying to repeat the same big and quick lateral movement with the same window multiple times in a row. Sometimes I can repeat the movement 20 times with no recurrence of the problem, but other times just a few repetitions are enough to encounter one occurrence where the window’s movement is abruptly interrupted, as if the window had hit an invisible wall.

As indicated in previous posts, I have done my best to rule out the most obvious possible causes. It is not a defective mouse. (The problem did not occur in Mac OS X 10.4 and the problem occurs with more than one mouse in Mac OS X 10.5.) It is not my mouse tracking surface. (I have a mousepad specially designed for optical mice, with a hard, non reflective surface, that I have been using for years, and I keep it clean.) It’s not USB Overdrive, because the problem also occurs when I don’t use the software.

I am pretty sure that it is a software problem—something in Mac OS X 10.5 itself that causes it to occasionally lose track of mouse movements. It is not as noticeable when you are simply moving your mouse pointer around (all mouse users are used to applying all kinds of small corrections to their mouse movements all the time), but when you are trying to drag an object (with the mouse button down) across a large area of the screen in a single movement, it is definitely noticeable. It does not happen every time. Sometimes it does not happen for a long time (several minutes), and then it starts happening again.

Maybe it depends on some background process that is running on and off and is interfering with the OS’s ability to track mouse movements accurately. I don’t know. But it is somewhat annoying and, contrary to what I wrote yesterday, unlike other similar problems (such as the occasional stuttering), it does not seem to have been really fixed in Mac OS X 10.5.2.

It could very well be that it is a problem specific to the USB architecture in Mac OS X 10.5, which has obviously undergone significant alterations from the one in Mac OS X 10.4, as indicated by the seemingly higher frequency of problems with USB devices causing kernel panics in Mac OS X 10.5. If that’s the case, we are probably going to have to wait until Apple addresses these USB-related problems in a future system update (not too far in the future, one hopes!).

This entry was posted by Pierre Igot on Wednesday, February 13th, 2008 at 4:45 pm and is filed under Macintosh. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.