Integrating OS power management with the X server

[Keith Packard]

> Why isn't a simple xrefresh() (i.e. asking all windows to redraw
> themselves) sufficient ?

The X server stores pixmap data in video memory, which cannot be
reconstructed in this manner.  I did fix the XFree86 DDX several years ago
to not store the contents of the screen as well, by using a  mechanism
equivalent to xrefresh.

The video card is also returned to whatever mode seen when the X server
started so that console messages can be seen while the machine is changing
power states.

This is all handled by the same mechanisms which deal with VT switching,
the only difference being that there is no VT switch in this case.

-keith