Note: re-opening #616 after v2-exp merge

What is broken?

This all started with lipgloss.HasDarkBackground timing out most (80%?) of the time when running in Windows Terminal.

After ignoring the problem for a few weeks, I finally decided to figure out what was happening: queryBackgroundColor sends an OSC 11 and a CSI DA1 request one after the other and is supposed to receive back (at least) one response of each type.

The code (with a couple of debug statements) running in the VSCode integrated terminal:

Read 25 bytes: "\x1b]11;rgb:1f1f/2424/3030\x1b\\"
Received sequence: "\x1b]11;rgb:1f1f/2424/3030\x1b\\", state: 0, command: 11, data: "11;rgb:1f1f/2424/3030"
Read 7 bytes: "\x1b[?1;2c"
Received sequence: "\x1b[?1;2c", state: 0, command: 16227, data: ""

The same code in Windows Terminal:

Read 16 bytes: "\x1b]11;rgb:1a1a/1b"
Received sequence: "\x1b]11;rgb:1a1a/1b", state: 5, command: 11, data: "11;rgb:1a1a/1b"
Read 7 bytes: "1b/2626"
Received sequence: "1b/2626", state: 5, command: 11, data: "11;rgb:1a1a/1b1b/2626"
Read 2 bytes: "\x1b\\"
Received sequence: "\x1b\\", state: 0, command: 11, data: "11;rgb:1a1a/1b1b/2626"
Read 16 bytes: "\x1b[?61;4;6;7;14;2"
Received sequence: "\x1b[?61;4;6;7;14;2", state: 2, command: 16128, data: ""
Read 16 bytes: "1;22;23;24;28;32"
Received sequence: "1;22;23;24;28;32", state: 2, command: 16128, data: ""
Read 7 bytes: ";42;52c"
Received sequence: ";42;52c", state: 0, command: 16227, data: ""

As you can see, the terminal response is being received in chunks. Lipgloss assumes that somehow we will always end the read on a sequence boundary, and:

• Resets the parser state between reads
• Sends every partial read to filter() regardless of the current parser state.

This causes filter() to:

• Fail to parse the color (the least of our problems)
• Fail to recognize the DA1 response, thus never exiting the loop until the cancel reader times out

What am I changing?

The patch makes sure that we only ever send complete sequences to filter(), while maintaining the parser state in between reads so that we can successfully complete parsing a sequence even if it's split inconveniently.

If you have any better ideas on how to implement this, please feel free to propose them :)

Side note, in all terminals I use the CSI DA1 request causes the terminal to return the background and foreground colors in addition to the DA1 response. I feel like maybe there's an opportunity to simplify queryBackgroundColor, but I don't know how this behaves in other terminal emulators.

• I have read CONTRIBUTING.md.
• I have created a discussion that was approved by a maintainer (for new features).