Inhibitions and suspend in powerdevil and plasma-workspace

[SignKirigami]

Hello everyone, I find it confusing that some inhibitions will prevent system 
from auto suspend, but not manually clicking suspend button, so I try to read 
source code of powerdevil and plasma-workspace.

As far as I can see, in plasma-workspace there is canSuspend function which 
will check systemd-inhibit from dbus, and return yes when login1 returns yes 
or challenge(some applications requests inhibition will lead to this). Suspend 
button uses this, but because canSuspend treats yes and challenge as the same, 
there is no difference whether systemd inhibition exists, that's why suspend 
button will ignore systemd inhibition.

In powerdevil, what canSuspend returns is used in function 
loadAllInactiveActions, which will create a new profile with canSuspend and 
give it to suspendsession action, let it determine auto suspend or not. There 
is another mechanism which really works called policyagent. It syncs with 
systemd inhibitions and has its own inhibitions related to settings and old 
program(like ktorrent). When suspendsesstion handles timeout, it checks 
policyagent to determine whether to suspend or not.

Now I wonder if these really work as expected? Do we need to check systemd 
inhibition and give a warnning before do actual suspend work when inhibition 
exists?