R devel - Jun 2022 - Writing Extensions for R under Windows: is it better for GUIs to communicate with R via Rgui.exe, Rterm.exe or R.dll?

Writing Extensions for R under Windows: is it better for GUIs to 
communicate with R via Rgui.exe, Rterm.exe or R.dll?

In the construction of extensions (GUIs) for R, in the establishment of 
communication, according to the options below:

1- Rgui.exe (via Windows API) vs. R.dll (embedded R)
2- Rterm.exe (via IPC) vs. R.dll (embedded R)

What are the advantages and disadvantages in each case?

I would like to take advantage of the email to thank Tomas Kalibera for 
his efforts in solving the problems
of R 4.2.0 communication and the Tinn-R project. Once fixed the issues 
in R that surfaced
due to using GraphApp (cross-platform GUI Library in C for Windows) it 
was possible to fix the communication issues in Tinn-R
with Rterm.exe and Rgui.exe. Version 9.01.XX.XX with the corrections 
will be released soon. At the moment we are in
extensive testing phase.

Thanks in advance,
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Jose Claudio Faria
UESC/DCET/Brasil
joseclaudio.faria at gmail.com
Telefones:
55(73)3680.5545 - UESC
55(73)99966.9100 - VIVO
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If you have software to deal with statistics, you have arms,
if you have good software, you have arms and legs,
if you have software like R, you have arms, legs and wings...
the height of your flight depends only on you.

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On Sat, 04 Jun 2022 03:43:39 +0000
jcfaria <joseclaudio.faria at gmail.com> wrote:
> Writing Extensions for R under Windows: is it better for GUIs to 
> communicate with R via Rgui.exe, Rterm.exe or R.dll?
Well, WRE section 8 is all about linking the GUI to R as a DLL. It does
mention the alternative approaches like Rserve or DCOM, but such
interfaces are limited to some extents.
> In the construction of extensions (GUIs) for R, in the establishment
> of communication, according to the options below:
> 
> 1- Rgui.exe (via Windows API) vs. R.dll (embedded R)
Setting aside the fact that Windows API is not cross platform (which
may be not the point if you're writing a Windows-only GUI), the
messages that the application accepts and interprets are not a part of
a documented interface, so while they tend to be stable (because
Windows is mostly stable in handing the same kinds of messages to the
applications running there), they may be broken (like in R 4.2.0).

Linking to R.dll has a higher initial cost of setting up (you have to
write those callbacks, you have to set up R_HOME...), but the interface
won't be broken without a good reason and a migration plan.
> 2- Rterm.exe (via IPC) vs. R.dll (embedded R)
The console interface might be better understood and more stable than
passing messages to windows. If you're writing some kind of universal
interface suitable for different applications, all of which run a
Run-Eval-Print Loop in the command line, this may be a better approach
to take instead of linking to them individually. Although not without
problems [*], this is probably more stable than talking to Rgui.exe by
means of SendInput().
> What are the advantages and disadvantages in each case?
The advantages of linking to R.dll include being able to set up all
kinds of callbacks (EditFile, Busy, dataentry/dataviewer/selectlist) to
make their behaviour fit the theme of your application. The
disadvantages include a higher initial cost of setting it up and maybe
having to recompile it for different versions of R.

-- 
Best regards,
Ivan

[*] Check out ConEmu <https://conemu.github.io/> source code for
workarounds they probably amassed for all kinds of applications that
would otherwise prefer to be running in the standard console window.