[Mono-list] mono/gtk on beagle bone black

[Bill Swartz]

We are looking at options for a UI on a beagle bone black for an embedded
system. The UI and embedded system will be connected by RS232. Mono/gtk is
one possibility. The lead for the UI development is concerned about system
response. His note is copied below. Does any one know of resources for using
mono/gtk on a BBB? If anyone has experience with mono/gtk on a BBB, we want
to take advantage of your knowledge.

Bill

from the UI dev:


1) We need have as close to 20ms response time to a click as possible. My
tests with GTK+ apps in XFCE on the Beagle Bone Black running either
Angstrom or Debian did not have reliable response times, and sometimes were
upwards of 1 second.  I haven't tested any Mono apps, but I would be
surprised if they were much better.  Even touch event response in XFCE alone
was not very deterministic.  (This was with the prebuilt OS's for the BBB. 
Optimizations could make this better, but it would have to be significantly
better).

2) The standard mouse drivers that the touchscreen uses on the above OSs do
not do proper touch position filtering/averaging and are nearly useless with
resistive screens being touched by a finger.  This could be fixed by a new
mouse driver, but I haven't dug into it yet.  (With an app running on SDL
directly to the framebuffer, doing the position filtering/averaging is easy,
although doing it at a driver level is still probably the right choice. 
Last I remembered, I had a rudimentary mouse event interpreter in place in
my UI framework).

3) Given that this is a purpose-build UI, I'm somewhat hesitant to bring
along the look and feel of a window manager.  The big thing that I suspect
that Mono would bring along, beyond what I've already built, is sub-window
drawing (I had this nearly implemented the last time I hacked on the code),
and out-of-the-box UI widgets (I have about 70% of the UI widgets the app
needs already done).  That would be valuable, but I'm concerned about
everything listed above and a few widgets aren't enough to offset those
concerns.

If anyone has performance data on Mono apps writing directly to the
framebuffer on an ARM SoC (ideally the Beagle Bone Black/BlueSteel, or
Raspberry Pi 2) that would be interesting.

-Kris




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