Transparent cursors in XFree86

My laptop used to have these fancy semi-transparent cursors, but my harddisk died and after a reinstall they were gone – just like that.
It took me a while to figure out how to do it. The cursor theme is called “whiteglass”, and it can be enabled in two ways. The easiest is to set the environment variable

XCURSOR_THEME=whiteglass

before starting the X server.
The other option is to change the file /etc/X11/cursors/core.theme to read:

[Icon Theme]
Inherits=whiteglass

Before the change it will say “core” instead of “whiteglass”.
Some people find the cursor too hard to find on the display when it is white and semi-transparent — and sometimes they’re right — and for them there is the theme “redglass” with red semi-transparent cursors. I find it a bit too intrusive, visually.