Google Summer of Code is paying off for OLPC. Manu Cornet, one of the lucky Google students, developed an OLPC dual-mode display simulator using Xephyr. We'll let Manu explain it:

This "gtk-theme-torturer" is an application to detect performance issues in GTK themes/engines. It does two things:

• For each of the most common widget types (very easy to add some more), it packs an instance of it in a container, and resizes/redraws it many, many times. You can set a "pain level" to determine the number of times widgets will get redrawn while scaling.
• It takes each one of the gtk_paint_* functions (implemented by the engines themselves) and tries all possible parameters configurations, including unusual values to see if the engine crashes.

The program also outputs detailed time measures