Experimental Physics and
Industrial Control System

Pete Jemian <[email protected]> · Wed, 28 Feb 2018 15:17:08 -0600

Whit:

At this time, MEDM is an orphan piece of software. There are no

developers assigned to maintain it. Fantastic that it still works and

is still useful. Great job to its developers! MEDM's true end of life

will coincide with that of MOTIF, which library it uses. Recently, some

have made code changes in response to specific problems, but MEDM has no

maintainer.

At the APS, we went through a decision process before making the

transition from MEDM to caQtDM. You might be interested in some of the

criteria we considered, as described in this PDF from 2013:

https://epics.anl.gov/bcda/Docs/2013-08-12-replace-MEDM-slides.pdf

One of the interesting criteria from that report is how each of the

display managers perform under heavy update load. Some of them have

built-in features to throttle the display update rate, even though

incoming PVs are updated faster.

Another criterion is the live display of 2-D images, such as a from a

camera.

Another criterion is the ability to move display objects based on EPICS

PV values (such as to animate the movement of some device relative to

others).

The decision to use caQtDM was based on many factors, one of the most

important was that we were currently using MEDM. In the end, it was

more important for us to maintain a consistent user experience between

MEDM and its chosen successor at APS. We started this transition last

year for the facility (XSD) beam lines, yet some of the XSD beam lines

still use MEDM.

One other aspect is that the synApps developers, who maintain software

used by many facilities beyond the APS, continue to write screens in

MEDM, then use adl2ui to convert them to caQtDM for local use. This

allows others to apply similar converter tools to translate the MEDM

screens for their Display Manager. Adding yet another display manager

(YADM, if I may) will increase this complexity further. One must

establish truly "good value" for YADM if its screens are to be shared

with others. Or a truly good translator from MEDM. Extra value if it

can translate between YADM, CSS, caQtDM, epicsQt, ... and all the rest

of the new ones.

Regards,
   Pete

On 2/28/2018 2:43 PM, Ryan Slominski wrote:

Whit,
   I'm not a maintainer of MEDM, but I'm interested in display managers and maintain WEDM (https://github.com/JeffersonLab/wedm).  I agree that Motif is an old technology and a proprietary file format requiring a custom parser and encoder isn't optimal today where most languages now provide XML and JSON support.  However, the cost of creating and maintaining a display manager from scratch is high, and there are many existing ones already.  So it is an interesting question whether it just makes more sense to use an existing one as requirements not met can usually be worked around.  At JLab we mostly rely on EDM, but we create custom applications (in whatever language) for very custom screens.

Ryan

-----
Hi Ryan,

That it is not a nightmare is one feature. MEDM is pretty great
considering how old it is, and it easy to compile/install.

IMO not looking like windows 95 would be a major improvement. Also, the
ability to easily add new displays, interfaces, and interface behaviors
is missing.

One thing that would be nice is if the "adl" format was something
standard like json. I have not looked at the MEDM code yet.

I have been looking for an excuse to play around with Dear ImGui. It
turns out that a display manager is an ideal use for it. ImGui is
written in c++ (actually it is written like c code). I don't care what
language is used but it is probably best to do everything in c++ for
speed purposes. There are a lot of wrappers for Dear ImGui.

Are you a maintainer of MEDM?

Cheers,
Whit

--
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Pete R. Jemian, Ph.D.                 <[email protected]>
Beam line Controls and Data Acquisition (BC, aka BCDA)
Advanced Photon Source,    Argonne National Laboratory
Argonne, IL  60439                    630 - 252 - 3189
-----------------------------------------------------------
      Education is the one thing for which people
         are willing to pay yet not receive.
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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System