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[PR #13208] Add support for the DECPS (Play Sound) escape sequence #29428

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opened 2026-01-31 09:34:51 +00:00 by claunia · 0 comments
claunia commented 2026-01-31 09:34:51 +00:00
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Original Pull Request: https://github.com/microsoft/terminal/pull/13208

State: closed
Merged: Yes

Summary of the Pull Request

The DECPS (Play Sound) escape sequence provides applications with a
way to play a basic sequence of musical notes. This emulates
functionality that was originally supported on the DEC VT520 and VT525
hardware terminals.

PR Checklist

Detailed Description of the Pull Request / Additional comments

When a DECPS control is executed, any further output is blocked until
all the notes have finished playing. So to prevent the UI from hanging
during this period, we have to temporarily release the console/terminal
lock, and then reacquire it before returning.

The problem we then have is how to deal with the terminal being closed
during that unlocked interval. The way I've dealt with that is with a
promise that is set to indicate a shutdown. This immediately aborts any
sound that is in progress, but also signals the thread that it needs to
exit as soon as possible.

The thread exit is achieved by throwing a custom exception which is
recognised by the state machine and rethrown instead of being logged.
This gets it all the way up to the root of the write operation, so it
won't attempt to process anything further output that might still be
buffered.

Validation Steps Performed

Thanks to the testing done by @jerch on a real VT525 terminal, we have a
good idea of how this sequence is supposed to work, and I'm fairly
confident that our implementation is reasonably compatible.

The only significant difference I'm aware of is that we support multiple
notes in a sequence. That was a feature that was documented in the
VT520/VT525 manual, but didn't appear to be supported on the actual
device.

**Original Pull Request:** https://github.com/microsoft/terminal/pull/13208 **State:** closed **Merged:** Yes --- ## Summary of the Pull Request The `DECPS` (Play Sound) escape sequence provides applications with a way to play a basic sequence of musical notes. This emulates functionality that was originally supported on the DEC VT520 and VT525 hardware terminals. ## PR Checklist * [x] Closes #8687 * [x] CLA signed. * [ ] Tests added/passed * [ ] Documentation updated. * [ ] Schema updated. * [x] I've discussed this with core contributors already. Issue number where discussion took place: #8687 ## Detailed Description of the Pull Request / Additional comments When a `DECPS` control is executed, any further output is blocked until all the notes have finished playing. So to prevent the UI from hanging during this period, we have to temporarily release the console/terminal lock, and then reacquire it before returning. The problem we then have is how to deal with the terminal being closed during that unlocked interval. The way I've dealt with that is with a promise that is set to indicate a shutdown. This immediately aborts any sound that is in progress, but also signals the thread that it needs to exit as soon as possible. The thread exit is achieved by throwing a custom exception which is recognised by the state machine and rethrown instead of being logged. This gets it all the way up to the root of the write operation, so it won't attempt to process anything further output that might still be buffered. ## Validation Steps Performed Thanks to the testing done by @jerch on a real VT525 terminal, we have a good idea of how this sequence is supposed to work, and I'm fairly confident that our implementation is reasonably compatible. The only significant difference I'm aware of is that we support multiple notes in a sequence. That was a feature that was documented in the VT520/VT525 manual, but didn't appear to be supported on the actual device.
claunia added the pull-request label 2026-01-31 09:34:51 +00:00
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Reference: starred/terminal#29428
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