copy/paste not working on remote screen sessions with kitty

[jrmd54]

Hello,

This tool is amazing; i integrated it in my workflow to copy/paste over ssh when the remote server has no X server.

I tested it with alacritty and kitty, and i found a small issue with kitty:

By using the osc binary, i am able to do the following:
alacritty/kitty + screen : copy/paste
alacritty/kitty + ssh : copy/paste

However, when opening a screen session after having connected to a remote server, copy/paste does not work if the used terminal is kitty.

Steps to reproduce:

open kitty terminal (tested with version 0.35.2)
$ssh remote
$screen
$echo foo | osc copy # 'foo' is not copied to clipboard

Using alacritty (tested with version 0.13.2) does not reproduce the issue.

In both case, the verbose option produced the same output:
2024-07-24T14:34:43+02:00 DEBUG logging started
2024-07-24T14:34:43+02:00 DEBUG term name: screen.xterm-256color, aliases: []
2024-07-24T14:34:43+02:00 DEBUG Setting screen dcs passthrough
2024-07-24T14:34:43+02:00 DEBUG Beginning osc52 copy operation
2024-07-24T14:34:43+02:00 DEBUG Ended osc52

(i assumed that since osc52 does not work within screen unless osc binary is used, the issue is related to osc and not kitty but i may be wrong)

[jrmd54]

By running kitty from another terminal (to obtain debug logs), using 'osc copy' through ssh+screen gives the following errors:
[157,734] [PARSE ERROR] Unknown DCS escape code: ␛]52;c;dG90bw==
[157,734] [PARSE ERROR] Unknown char after ESC: 0x5c

(where ␛ corresponds to 0x241b)

[jrmd54]

With the latest version of the project, I found a fix for the issue:

Cf this blog post that uses 'BEL ESC BS' as terminator sequence for osc52 copy when inside screen instead of current 'ESC BS ESC BS',

replacing

	if isScreen {
		debugLog.Println("Setting screen dcs passthrough")
		oscOpen = DCS_OPEN + oscOpen
		oscClose = oscClose + DCS_CLOSE
	} else if isTmux {

with

	if isScreen {
		debugLog.Println("Setting screen dcs passthrough")
		oscOpen = DCS_OPEN + oscOpen
		oscClose = string(BEL) + oscClose
	} else if isTmux {

seem to do the trick.

However this seems to break copy for other terminals (such as alacritty) when inside screen, and I don't see an elegant way of performing a check without relying on envvars...