[ESS] C-c C-c in R console buffer causes Control key to get "stuck" (Windows)

[Mark Seeto]

Dear ESS group,

When I press C-c C-c using the right (not left) Control key in the R
console window (the Emacs buffer named "*R*"), Emacs starts acting as
though the Control key is being held down. For example, if I press C-c
C-c Return in the R console buffer (to cancel a partially entered
command), I get the message "<C-return> is undefined", and it keeps
happening with further key presses (e.g. pressing p moves to the
previous line). The problem doesn't happen if I press C-c C-c in the R
console buffer using the left Control key. Even other programs (e.g.
Notepad, Firefox) start acting as though Control is being pressed.

The "stuck" Control key can be "released" by pressing the left Control
key, and that's the only thing I know of that fixes it.

If I press C-c C-c (using either Control key) in an Emacs buffer with
a .R file, the problem doesn't happen, and code is sent to the R
console as expected. As far as I know, the problem only happens if I
press C-c C-c using the right Control key in an R console buffer.

The problem happens using the laptop keyboard and also using an
external keyboard plugged into the laptop.

I'm using Windows 10, Emacs 26.3 (Vincent Goulet's version), ESS
18.10.2, R 3.6.1.

The problem doesn't happen using Emacs 25.2 (Vincent Goulet's
version), ESS 16.10, R 3.6.1 on the same computer

The same thing happens when I try it on a different Windows 10
computer (problem happens with Emacs 26.3, ESS 18.10.2, but not with
Emacs 25.2, ESS 16.10).

To try to investigate further, I installed ESS 18.10.2 on my Emacs
25.2 but I then couldn't start R - I got the message "Wrong type
argument: consp, nil".

I don't know that ESS is causing the problem, but since it only starts
happening when I'm in an R console buffer in Emacs, I thought this
would be a good place to ask about it.

I would be grateful for any ideas on how to prevent this problem from
happening. Thanks also to the ESS team for providing ESS, and to
Vincent Goulet for providing his modified Emacs.

Mark Seeto
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