But I disagree that the correct cursor to use for a blocking task that cannot be cancelled is the spinning beachball of death. That cursor after all is the cursor automatically provided by the operating system when an application is not responding to input events. As such when I see the beachball I associate it with a stuck application, one that may need to be forcibly quit.
Previous versions of Photoshop showed the watch cursor for actions which took a significant length of time. Showing the watch cursor is friendlier than showing the beachball of death because it indicates that the application is busy, too busy to handle your clicks but everything is hunky dory and the train will arrive at the station.
There is no watch cursor listed in Apple’s documentation on cursors. However the cursor is still present in the system and can be found in the headers for the carbon appearance manager:
kThemeWatchCursor = 7, /* Can Animate */
If you have Xcode 3.2.2 installed you can find this in
/Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Carbon.framework/Versions/A/Frameworks/HIToolbox.framework/Versions/A/Headers/Appearance.h, line 634.
I don’t know enough about Macintosh programming to say whether it is possible to employ this cursor from a Cocoa-based application.