Bug#457596: when -fb not provided
Dan Jacobson wrote:
Reconfigures the screen to the specified size. All config-
ured monitors must fit within this size. When this option
is not provided, xrandr computes the smallest screen size
that will hold the set of configured outputs; this option
provides a way to override that behaviour.
is incorrect. When this option is not provided, the action is the same as
-q When this option is present, or when no configuration
changes are requested, xrandr will display the current
state of the system.
unless other options are provided.
Since you apparently tried multiple xrandr commands and now know very
well how xrandr works, you should be able to write a patch for the
manpage (or for the code if you think the behavior isn't logic). Sending
the patch to the upstream dev (by opening a bug on
bugzilla.freedesktop.org) would be very nice.