Some items may only display in certain modes, like when doing a
remote display.  Multiple values can be specified and must be
separated with commas.  The following values are possible:
console - In console mode.
console-fixed - In console non-flexi mode.
console-flexi - In console & flexi mode.
flexi - In flexi mode.
remote - In remote mode.
remote-flexi - In remote & flexi mode.
For example:
<show modes="flexi,remote"/>
You can also specify the "type" value to indicate that certain items
should only be displayed if the type is true.  Valid values include
the following:
chooser, if ChooserButton is set to "true" in
gdm.conf file.
config, if ConfigAvailable is set to "true" in
gdm.conf file.
halt, if HaltDaemon is specified in
gdm.conf file.
reboot, if RebootCommand is specified in
gdm.conf file.
suspend, if SuspendCommand is specified in
gdm.conf file.
system, if SystemMenu is specified in
gdm.conf file
timed, if TimedLoginEnabled is set to "true" in
gdm.conf file.
For example:
<show modes="console" type="system"/>
Note that if SystemMenu is off then all of halt, reboot, suspend,
chooser and config will not show, so this is a global toggle for them
all.  See some of the standard themes for how the show modes
are used.
