Optimize|libdeng2|Observers: Ensure Loop does not copy the observer set
Profiling showed that iterating through audiences using Observers::Loop had unexpectedly slow performance due to Loop accessing the data in a non-const manner and thus forcing Qt to make a copy of the audience (which needed to be deleted by ~Loop).
This commit ensures that Loop accesses the set in const mode, taking advantage of implicit sharing.
Optimize|libdeng2|Observers: Ensure Loop does not copy the observer set
Profiling showed that iterating through audiences using Observers::Loop
had unexpectedly slow performance due to Loop accessing the data in
a non-const manner and thus forcing Qt to make a copy of the audience
(which needed to be deleted by ~Loop).
This commit ensures that Loop accesses the set in const mode, taking
advantage of implicit sharing.