# 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.

## 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>.