Re: An alternative to MDI / new WM feature ?

Alan Shutko <> writes:
> >>>>> "J" == John Kodis <> writes:
> J> On Fri, Apr 10, 1998 at 06:08:44PM +0000, Jens Ch. Restemeier
> J> wrote:
> >> There's another WM / X related thing I wanted to ask for some time:
> >> Multiple monitor support.
> J> It's already supported, at least by some X servers.
> Can you pick up a window and move it to another screen?  If not, it's
> still not supported.

This is a fairly fundamental limitation of X. Once a window is
created, its depth, visual, and screen are immutable. Since screens
may support different sets of visuals, it is generally not possible.

It could be faked by cooperation between the window manager and
clients, though. When the window was dragged off the edge of a screen,
the window manager could signal this to the client which would kill
the old window and create a replacement on the new screen. It would
then relay the new window id back to the window manager. This would
require modifications to clients to support the protocol with the
window manager.

It could also be solved by an X protocol extension, but of course
since this extension revokes guarantees clients would have to be

Both of these options would not allow windows that span monitors (the
assumption that a window has a uniform visual seems to me to be
something too fundamental to change).

Macs have always supported dragging window between monitors, but I've
never done any programming on Macs so I don't know how they manage
it. Windows will soon support dragging windows between monitors, but
this is a different matter; unless they restrict this to screens with
the same depth I expect to see an awful lot of Windows apps breaking.
If the "same depth" restriction is acceptable, then an X server could
fake it by pretending that it is one big screen (with perhaps a little
magic to make the "virtual screen" rectangular). Does anyone know what
approach Windows uses?

Dave Wragg

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