This is described a bit more here: https://lists.gnu.org/archive/html/qemu-devel/2016-05/msg00946.html
But basically it's a libsdl bug: https://bugzilla.libsdl.org/show_bug.cgi?id=3287 ** Bug watch added: bugzilla.libsdl.org/ #3287 http://bugzilla.libsdl.org/show_bug.cgi?id=3287 -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1615212 Title: SDL UI switching to monitor half-broken and scrolling broken Status in QEMU: New Bug description: ctrl+alt+2 must be pressed 2 or more times for the monitor console window to appear with -sdl, the window flashes and disappears also before finally staying open To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1615212/+subscriptions
