[Rd] Writing in R // R 4.2.0 on Windows doesn't work with Dasher

[Ivan Krylov]

On Sun, 15 May 2022 11:10:49 -0300
Paulo Barata <pb using infolink.com.br> wrote:

> I noticed today that R 4.2.0 responds to the "Enter" character of
> Dasher version 5.0.0 beta in "Direct Entry" mode. An "Enter" in
> Dasher causes the R prompt to jump to the next line, as an "Enter"
> should do.
> 
> No other characters (letters, digits, special characters like + = & ~
> | # $) are accepted by R 4.2.0 through Dasher.

This seems to be very similar to the problem discussed here:
https://stat.ethz.ch/pipermail/r-devel/2022-May/081683.html

For the record, here's the part of Dasher responsible for "Direct
Entry" on Windows:
https://github.com/dasher-project/dasher/blob/0ec7d646dbaadf06b8eebfc11b784738a20e75af/Src/Win32/Widgets/Edit.cpp#L302

MSDN says:

>> If KEYEVENTF_UNICODE is specified, SendInput sends a WM_KEYDOWN or
>> WM_KEYUP message to the foreground thread's message queue with
>> wParam equal to VK_PACKET. Once GetMessage or PeekMessage obtains
>> this message, passing the message to TranslateMessage posts a
>> WM_CHAR message with the Unicode character originally specified by
>> wScan.

<https://docs.microsoft.com/en-us/windows/win32/api/winuser/ns-winuser-keybdinput>

Previously, Tomas Kalibera has mentioned:

> For Unicode Windows, GraphApp uses WM_IME_COMPOSITION messages to
> read the keys instead of WM_CHAR, which it uses for non-Unicode
> windows.

I think that for a combination of R >= 4.2 and Dasher, this means an
impasse. Either Dasher should be taught to send WM_IME_COMPOSITION
messages to R (?), or R should learn to understand WM_CHAR messages in
its Unicode windows in addition to WM_IME_COMPOSITION it currently uses.

-- 
Best regards,
Ivan