workspace: Only consider windows that should be showing as focusable
When selecting the default focus window, is_focusable() was not considering the new conditions for whether a window should be shown or hidden that were added to meta_window_should_be_showing() in 39942974. As a result the default focus window could end up a window already hidden or hidden once meta_window_flush_calc_showing() is called by meta_window_focus() when focusing the default window. This would cause meta_window_focus() to fail, which is an issue if it prevents us from unfocusing a window when it is getting unmanaged.
Fixes: 39942974 ("x11: Integrate frames client into Mutter") Closes: #2644 (closed)
Edited by Sebastian Keller