> I have a question about "tmfe approach" to implementing MIDAS frontends. If I read the code correctly, 
> within this approach it is the TMFeEquipment things, not the TMFrontend's themselves, 
> which handle the run transitions - the TMFrontend class

that's correct and it is documented so in https://bitbucket.org/tmidas/midas/src/develop/tmfe.md

> So how does a user control the sequence in which TMFeEquipment::HandleBeginRun functions of different 
> TMFeEquipment pieces are called at begin run? - there are two cases to consider: TMFeEquipment things 
> defined by the same TMFrontend and by different TMFrontend's.

I am not sure what you are trying to do. It is always easier to suggest a solution to a specific problem.

But I will try to answer anyway:

1) "time ordering of run transitions" - of course midas transitions are ordered by transition sequence numbers 
and the tmfe class provides methods to control this. ditto for the mfe.cxx frontends.

2) for one TMFrontend, the order of calling HandleBeginRun() is the order in which equipments were added to the 
equipment using FeAddEquipment(). HandleEndRun() is called in reverse order. (I better check this).

3) to have multiple TMFrontends in one program would be unusual (mfe.cxx frontends completely do not support 
this), but should work. Everything was coded to support this, but it was never tested in practice because we 
cannot invent any useful use-case for it. HandleBeginRun() handlers are likely to be called in the frontends are 
created. (I could check this and confirm it works, as long as you have a valid use-case for this configuration).

4) Frontend X has EquipmentA and EquipmentB, you want EqA::HandleBeginRun() to be called at run transition 200 
and EqB::HandleBeginRun() to be called at run transition 400.

This is not directly supported by mfe.cxx frontends (the begin_run() handler is a global function) and I did not 
directly implement it in the TMFE frontend.

But I think this would be a useful improvement. I will look into this.

Likely I will add per-equipment data members fEqConfBeginRunSeqNo, fEqConfEndRunSeqno, etc. Value 0 would 
unregister the corresponding run transition handler. This would cleanup the code quite a bit, a bunch
of RegisterTranstionXXX functions could go away.

K.O.