Experimental Physics and
Industrial Control System

One of the original objectives for edm was to build a display manager to which other,
perhaps remotely located, developers could contribute. The biggest potential problem was
avoiding namespace collisions.

Suppose you and I both wish to build a text display widget that may be used by other
sites.

If I build a widget, I must pick two global symbols. For example, for a text display
widget I could choose the following:

 create_textDisplayWidgetPtr
 clone_textDisplayWidgetPtr

The widget then gets packaged into a shareable library named, for example,
libTextDisplayWidgetLibrary.so.

These names are descriptive but might be vulnerable to colliding with names
associated with the widget you build.

As a result, I suggested using uuid-derived names. I pick my names by issuing
the uuidgen command, which gives something like

 create_5c2fdd15_0dcf_4ead_b0e4_cdbe653e5637Ptr
 clone_5c2fdd15_0dcf_4ead_b0e4_cdbe653e5637Ptr

To examine contents:
edm -show [full path to library]/lib5c2fdd15-0dcf-4ead-b0e4-cdbe653e5637.so

To add widgets to the edm objects file:
edm -add [full path to library]/lib5c2fdd15-0dcf-4ead-b0e4-cdbe653e5637.so

2/ Where did I go wrong in the GIF widget configuration ? I did
something very similar for the PNG widgets and it worked immediately
(kudos!).

There might have been a problem with the gif c++ file (A fix was released
in version 1-11-0t on 6-Mar-2007 that was related to the gif object global names).

3/ EDM is very similar to medm. Ok, you can create new widgets, but is
this really worth the transition?

medm is a fine piece of work. In our case, we were using a non-epics commercial
product from Vista Control Systems. After switching to EPICS, we wanted a few additional
medm features that were present in the Vista display manager. I spoke with Ken Evans
about this and was left with two distinct impressions:

 1) It was somewhat difficult to add new features to medm
 2) My request had a very low probability of being implemented

This inspired me to take a shot at writing an extensible display manager. I spent the
next six weeks, at home, in the evenings and on weekends, developing edm. Over
the years, edm has evolved considerably as a result of many excellent comments,
criticisms, and contributions from various EPICS developers and users.

Some sites still use DM2K or edd/dm. The new java-based tools are on the
horizon and soon edm itself will be obsolete.

6/ Why does (almost) none of the epics software work out of the box?
Keep that one for later, that another $64K question

Community-based software suites like EPICS unfortunately require some degree of user
participation. We just can't keep up with new platforms, new os/library distributions,
new include file organizations, new compiler behavior/constraints, new make quirks, etc.

On Tue, 2007-04-10 at 18:27 -0700, Emmanuel Mayssat wrote:

So I update my edmObjects file accordingly with the following entry.

cf322683-513e-4570-a44b-7cdd7cae0de5 /EPICS_EXTENSIONS/lib/linux-x86/libcf322683-513e-4570-a44b-7cdd7cae0de5.so Graphics GIF Image

After listing the symbols of this library, I find ...

nm /home/cxsfs/bluice/devel/epics-extensions/lib/linux-x86/libcf322683-513e-4570-a44b-7cdd7cae0de5.so | grep create


000083ec T create_cfcf6c8a_dbeb_11d2_8a97_00104b8742dfPtr

(another great name!)

cfcf6c8a_dbeb_11d2_8a97_00104b8742df /EPICS_EXTENSIONS/lib/linux-x86/libcf322683-513e-4570-a44b-7cdd7cae0de5.so Graphics GIF Image

and it works.

Questions still remain...

Questions:
1/ Where are those library names coming from ? How are they generated?
2/ Where did I go wrong in the GIF widget configuration ? I did
something very similar for the PNG widgets and it worked immediately
(kudos!).
3/ EDM is very similar to medm. Ok, you can create new widgets, but is
this really worth the transition?
4/ Is someone maintaining a library of edm widgets?
5/ Is there any other display manager worth the try?
6/ Why does (almost) none of the epics software work out of the box?
Keep that one for later, that another $64K question ;-)

Regards,
--
Emmanuel

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References:

Building and crashing EDM Emmanuel Mayssat

Re: Building and crashing EDM Emmanuel Mayssat

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