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Case Study 3 - ALM’s Blood

Blood is “an absolutely useless control panel” for System 7 by Alessandro Levi Montalcini “that puts some drops of blood right on your desktop” when the machine starts up. I installed it one day under Mac OS 9.1 to try it out.

I made the assumption that the program created a set of global floating windows – one per droplet – and began to wonder how it would cope with other such windows, for example A-Dock and ICQ’s global floating window; that is, what would happen if you dragged a blood droplet window over a global floating window. As you can see below, it has a few difficulties dealing with them, as they are not ever requested to be redrawn and blood is left all over them.

The most surprising part is what it does to the menu bar. You can see below that although I can make a global floating window get redrawn, the droplets eat permanent holes in the menu bar.

The next time the menu bar is updated, the holes disappear, but the menu bar is permanently broken. Watch what happens if I drag a window up under the menu bar with live window dragging enabled with Power Windows:

Even more fun is what happens if I then drag the window away after the menu bar has been refreshed: it rips pieces of the menu bar away with it.

Live dragging is very much messed up by the holes in the menu bar, as you can see from the next screenshot:

Even if you do not have the Power Windows control panel installed, you can still have some fun. Remember that icon at the top left of the screen? If you now click on it, the holes in the menu bar cause it to be drawn over the top of the menu bar. The Finder then updates the menu bar and draws it back. However, if you then click on the filename of another item, it draws the folder icon as unselected and leaves it visible over the top of the menu bar.

My best guess is that the droplets are implemented by actually altering the menu bar’s QuickDraw region, so by dragging one over the menu bar and then away from it, it causes a circle to be deleted from the region which removes part of the rectangular region that is meant to enclose the menu bar. Switching the menu bar off and back on seems to cause it to get repaired. The droplets also have their own issues: after one has been sat at a point on the screen for too long, it eats a hole in the screen where no more droplets will show up.

If a droplet co-incides with one of these holes, no screen updates occur within the hole, as you can see with the following screenshot: the Control Strip doesn’t exist where the droplet and hole co-incide. After a while, though, the holes themselves vanish.

Alessandro describes his work as “an absolutely useless control panel” but that is not quite true. It was good fun! Cheers to Mr Anonymous for returning me the screenshots and HTML after I lost them, permitting me to post this to public Internet.