readline: make ctrl-l clear screen & redraw line

[jepler]

.. similar to how standard Python does it.

Closes: #6635

[gamblor21]

The code looks good, the control string works when I copy it to PuTTy but I'm having issues (on my end and ran out of time) testing it so I do not want to approve just by myself.

[tannewt]

Want to make this work in Terminal too? (For displays that echo the serial output.)

[jepler]

If by "Terminal" you mean the mac terminal program / command window, I don't have a mac to test on. I only tried xfce4, a standard-ish terminal on Linux, based on the list of ANSI escape codes at https://en.wikipedia.org/wiki/ANSI_escape_code#CSI_(Control_Sequence_Introducer)_sequences (though I was reading a different reference the wikipedia codes match)

If it's not widely compatible then we can just close this up, I'm not a terminal expert.

[tannewt]

I mean CP's Terminal: https://github.com/adafruit/circuitpython/blob/main/shared-module/terminalio/Terminal.c#L52=

[jepler]

Using CSI 2 J might be worth trying, that's "clear entire screen" instead of "clear to end of screen". After the cursor has moved to 0,0 with CSI H, they should be the same, and so I chose the sequence that was shorter by 1 byte.

[jepler]

oh! taking a quick look at that code, it may be that the fix is to use the sequence CSI ; H as the H-parsing only comes after a ';' is encountered.

[jepler]

oh yes and only CSI 2 J is supported by the terminal class too

[jepler]

OK it's now tested on a pyportal. In addition to the problem of the incompatible escape sequences, it was originally inside a disabled #if block, but one that is enabled in the 'unix port' which is where I had tested initially.

[gamblor21]

Works in PuTTY now. The ifdef was why it wasn't working for me before.

[tannewt]

#6608 includes a fix for the build that runs out of space.

done!

[tannewt]

Thank you!