Garbage left in input buffer on urxvt with transparent background color set

[tejing1]

• urxvt -fg white -bg rgba:0000/0000/0000/C000
• Inside the terminal, run gh --version, or most anything that calls termenv.DefaultOutput().BackgroundColor() I've also personally noticed what seems to be the same issue with https://github.com/numtide/treefmt
• Garbage characters are left behind and read by your shell, or whatever next reads from the terminal.

Here's the leftover input buffer contents (with 2 ctrl-d's to flush it through hexdump):

$ gh --version; hexdump -C
^[]11;rgba:0000/0000/0000/c000^[^[[114;1Rgh version 2.72.0 (nixpkgs)
https://github.com/cli/cli/releases/tag/v2.72.0
00000000  5b 31 31 34 3b 31 52 1b  5d 31 31 3b 72 67 62 61  |[114;1R.]11;rgba|
00000010  3a 30 30 30 30 2f 30 30  30 30 2f 30 30 30 30 2f  |:0000/0000/0000/|
00000020  63 30 30 30 1b 1b 5b 31  31 34 3b 31 52           |c000..[114;1R|
0000002d

Context: https://github.com/cli/cli/issues/10830

Thanks, @ei-grad for tracking this down.

[ei-grad]

A simple fix could be:

diff --git a/termenv_unix.go b/termenv_unix.go
index bef49ca..7622e97 100644
--- a/termenv_unix.go
+++ b/termenv_unix.go
@@ -223,7 +223,7 @@ func (o *Output) readNextResponse() (response string, isOSC bool, err error) {
                }

                // both responses have less than 25 bytes, so if we read more, that's an error
-               if len(response) > 25 { //nolint:mnd
+               if len(response) > 64 { //nolint:mnd
                        break
                }
        }

However, this will result in incorrect color parsing. I looked deeply into the urxvt color conversion code, but couldn't find a good solution.

[tejing1]

I can confirm that patch resolves the input buffer issue. I'm already using it as a local solution.

Properly parsing urxvt's response is obviously ideal, but bad color detection is still a big step up from "gh is unusable." 🙂