# Query Disallowed Features (OSC 61)

> Ask xterm which parts of one of its guarded features are refused while that feature is off.

- **Sequence:** `OSC 61 ; Pt ST`
- **ECMA-48:** [§8.3.89 OSC – Operating System Command, p. 51](https://archive.org/details/ecma-48-5th-edition-june-1991/page/n64/mode/1up)
- **xterm:** [Operating System Commands](https://invisible-island.net/xterm/ctlseqs/ctlseqs.html)

XTQDISALLOWED, `OSC 61 ; resource ST`, asks xterm which parts of one of its
guarded features are refused while the feature's `allow…` resource is off.
`resource` is one of the names [OSC 60](https://control-codes.page/osc/allowed/index.html.md) reports, such as
`allowWindowOps`, and the answer is `OSC 61 ; list ST`, the parts by name,
separated by commas, in xterm's own order
([`unparse_disallowed_ops`](https://github.com/ThomasDickey/xterm-snapshots/blob/xterm-411a/charproc.c#L10666-L10699)).
The list is the feature's `disallowed…` resource: `disallowedWindowOps` for
`allowWindowOps`, and so on.

In a default xterm, `allowWindowOps` is off, and the window operations it
refuses are the ones in the default `disallowedWindowOps`: reporting the
icon name and the title, setting X properties, reading and setting the
selection, and the checksums of [DECRQCRA](https://control-codes.page/csi/decrqcra/index.html.md). Everything else
in [XTWINOPS](https://control-codes.page/csi/xtwinops/index.html.md) is allowed. The case follows it.

This is xterm's own, and libghostty-vt does not have it, so the case is a
known difference.

## Support

| Terminal | Version | Support | Notes |
| --- | --- | --- | --- |
| VT220 | [manual](https://vt100.net/docs/vt220-rm/), 2nd ed., 1984 | No | OSC is not among the controls it recognizes ([§4.2](https://vt100.net/docs/vt220-rm/chapter4.html#S4.2)) |
| VT510 | [manual](https://vt100.net/docs/vt510-rm/), 1st ed., 1993 | No | ignores an OSC string ([chapter 4](https://vt100.net/docs/vt510-rm/chapter4.html)) |
| xterm | patch 412, [xterm-411a](https://github.com/ThomasDickey/xterm-snapshots/tree/xterm-411a) | Yes |  |
| libghostty-vt | [0f171f6](https://github.com/ghostty-org/ghostty/tree/0f171f650a1cbbd6df4a2573b6b0c7de57cc6d90) | No | OSC61-1: not implemented |
| Konsole | 26.11.70, [a24c3d71](https://invent.kde.org/utilities/konsole/-/tree/a24c3d71be3684f24d030aa2dbe9bd723d985233) | No |  |
| ConEmu | build 230724, its [documentation](https://conemu.github.io/en/AnsiEscapeCodes.html) | No | not in ConEmu's list, [ANSI escape codes](https://conemu.github.io/en/AnsiEscapeCodes.html) |

## Validation

### OSC61-1: Which window operations are refused

*A known difference: libghostty-vt does not pass this case.*

Input, one step per line:

```text
\e]61;allowWindowOps\a
```

Expected screen:

```text
|______|
reply \e]61;GetIconTitle,GetWinTitle,SetXprop,GetSelection,SetSelection,GetChecksum\a
```

---

This is the Markdown version of <https://control-codes.page/osc/disallowed/>. On that page every validation case runs live in libghostty-vt, the terminal emulation core of Ghostty, compiled to WebAssembly.

The validation cases are written in the notation described in <https://control-codes.page/notation/index.html.md>.