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feat(term): synchronized output (DEC mode 2026) via the sync-output capability - #139
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… capability Full-screen frames wrap in BSU/ESU when RuntimeCapabilities.syncOutput is true; the flag rides reduce() per frame so a capability flip takes effect on the next rendered frame with no invalidation signal. Zero-diff frames emit zero bytes even when wrapped, and line mode is never wrapped. Renderer-spec 7.9 discharges the deferral recorded in 7.8.
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Changeset suggestionThe current changeset no longer matches this PR. This review contains a corrected replacement. Why: Changeset package scope does not match the affected packages confidently. Changeset contains implementation or roadmap noise. View the proposed changeset---
'@bomb.sh/tty': minor
---
Adds synchronized output (DEC mode 2026) driven by the `sync-output` capability.
When `RuntimeCapabilities.syncOutput` is true, every full-screen render is wrapped in Begin/End Synchronized Update (`CSI ? 2026 h` / `CSI ? 2026 l`) so the terminal presents the frame as one atomic repaint. No-op frames emit nothing even when wrapping is active. Line-mode renders are never wrapped.
`syncOutput` is raised by three channels: the `Sync` extended capability in the parsed terminfo entry, the `TMUX` environment variable, and probe replies (DECRPM 2026 and XTGETTCAP `Sync`). Probe replies take precedence in both directions — a DECRPM 0 or 4 reply clears the capability even when detection seeded it.
#### Migration
`Capabilities` gains a new required field and `reduce` gains a new `sync` parameter.
```diff
- interface Capabilities {
+ interface Capabilities {
readonly styledUnderline: boolean;
+ readonly syncOutput: boolean;
}
```
```diff
- reduce(ct, buf, len, mode, row, deltaTime);
+ reduce(ct, buf, len, mode, row, deltaTime, sync);
```
Pass `0` for `sync` to preserve the previous unwrapped behaviour, or forward `RuntimeCapabilities.syncOutput ? 1 : 0` to enable wrapping.Review this changeset manually If this draft is correct, react with 🚀 and Cooper will commit it to this branch. |
![bombshell-cooper[bot]](https://avatars.githubusercontent.com/in/4226441?s=60&v=4){kind=small}
| @@ -0,0 +1,7 @@ | |||
| --- | |||
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There was a problem hiding this comment.
Changeset needs revision.
Changeset package scope does not match the affected packages confidently. Changeset contains implementation or roadmap noise.
View the proposed replacement
---
'@bomb.sh/tty': minor
---
Adds synchronized output (DEC mode 2026) driven by the `sync-output` capability.
When `RuntimeCapabilities.syncOutput` is true, every full-screen render is wrapped in Begin/End Synchronized Update (`CSI ? 2026 h` / `CSI ? 2026 l`) so the terminal presents the frame as one atomic repaint. No-op frames emit nothing even when wrapping is active. Line-mode renders are never wrapped.
`syncOutput` is raised by three channels: the `Sync` extended capability in the parsed terminfo entry, the `TMUX` environment variable, and probe replies (DECRPM 2026 and XTGETTCAP `Sync`). Probe replies take precedence in both directions — a DECRPM 0 or 4 reply clears the capability even when detection seeded it.
#### Migration
`Capabilities` gains a new required field and `reduce` gains a new `sync` parameter.
```diff
- interface Capabilities {
+ interface Capabilities {
readonly styledUnderline: boolean;
+ readonly syncOutput: boolean;
}
```
```diff
- reduce(ct, buf, len, mode, row, deltaTime);
+ reduce(ct, buf, len, mode, row, deltaTime, sync);
```
Pass `0` for `sync` to preserve the previous unwrapped behaviour, or forward `RuntimeCapabilities.syncOutput ? 1 : 0` to enable wrapping.
|
Size Increased — +0.6 KB 123.3 KB unpacked |
commit: |
Per the approved spec amendment (terminfo-spec §6.1/§6.3/§7.1/§7.2/§8/§9.1, renderer-spec §7.9): syncOutput is raised only on positive evidence from three channels. - Probe row 8: XTGETTCAP Sync (DCS + q 53796e63) as its own request — some terminals honor only one capability per XTGETTCAP request, so it must not merge into the RGB;Tc query. A value-carrying reply confirms; a reply naming Sync without a value denies. Sync replies never touch the colordepth tally. - Static Capabilities gains syncOutput, seeded from the Sync extended capability in the parsed terminfo entry and from TMUX environment evidence (tmux consumes mode 2026 from inner applications). - TINV-3 precedence: probe replies outrank detect-time seeding in both directions; runtimeFromStatic now flows the seeded field through. The reply's sequence value is discarded in v1: emission remains the DEC mode 2026 form, unchanged from §7.9's normative rules.
natemoo-re
marked this pull request as ready for review
October 12, 2026 01:04
cowboyd
reviewed
Oct 12, 2026
| mode, | ||
| row, | ||
| dt, | ||
| currentCaps.syncOutput ? 1 : 0, |
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I thought we were going to move capabilities into the native state rather than copy them over on every call.
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Author
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That was indeed the direction we discussed! Oversight on my part, I'll take another pass at this.
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Implements synchronized output (DEC mode 2026), previously deferred in renderer-spec §7.8.
When
RuntimeCapabilities.syncOutputis true, each full-screen frame is wrapped in BSU/ESU (CSI ? 2026 h/CSI ? 2026 l) so the terminal presents it as one atomic repaint, which prevents tearing mid-frame.