ThrottledCursor

On some Linux/XFree installations this drives the CPU usage of the X server through the roof.

If you observe that store goes faster if you move the mouse outside the VW windows, try this ThrottledCursor package.

Note: this package does not unload cleanly, you may get a (harmless) UHE.

ThrottledCursor is written for VW7.

Reinout Heeck

See this vwnc message for an alternate implementation.

Other Cool Things in the Open Repository

It seems Andres' package now is better maintained than Throttled cursor, it also tackles the problem of 'stuck' cursors. See this vwnc message.

It turns out this package is useful on Windows as well, Steven Kelly reports (www.parcplace.net/list/vwnc-archive/0508/msg00016.html)

ThrottledCursor useful for WinXP Remote Assistance

I noticed our app runs really slowly for some operations over Windows XP Remote Assistance (desktop sharing over the network). Opening a simple window took no time at all on the host PC, but the remote client display of the desktop took 10-15 seconds to update. A little testing showed it was to do with rapid Cursor changes read<->execute<->wait on those operations. A vague memory and the vw-dev list archive turned up [...ThrottledCursor].

I tried it out, and it solved the problem perfectly. Since the same 'hack' (actually very nice multiprocess code) has been useful twice, I thought mentioning it again might help others who hit similar problems. The package is available in the Open Repository as ThrottledCursor (originally for a pre-release of VW7, seems to work fine in 7.1).

To do

• code to make loading/unloading safe
• parcel comment
• Peer review of BinarySemaphore (it hasn't been stress tested).
• BinarySemaphore really needs to be moved to another parcel or the base.
• Remove assertion "Provide an error notification if the argument is not a Cursor" from #currentCursor: comment since it is false.
• Bump process priority a couple of notches (to 55?) to make space for app-specific priorities below that of ThrottledCursor's.
• Mark our process as a system process.

I played a bit on my Linux box:

(Delay forSeconds: 2) wait.
Time millisecondsToRun: [
	1000 timesRepeat: [
		Cursor wait show.
		Cursor normal show]]

If I leave the pointer over a VW window this reports roughy 45 seconds. If I move my pointer outside all VW windows it's 40 _milli_seconds.

The above code snippet reports roughly 200 ms with ThrottledCursor loaded.