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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. View the proposed changeset---
'@bomb.sh/tty': minor
---
Adds synchronized output (DEC mode 2026) to full-screen rendering.
When `RuntimeCapabilities.syncOutput` is true, every full-screen frame is wrapped in Begin/End Synchronized Update (`CSI ? 2026 h` / `CSI ? 2026 l`) so the terminal presents the frame as one atomic repaint without tearing. No-op frames and line-mode output are never wrapped.
`Capabilities.syncOutput` is raised by three evidence sources, in precedence order: a DECRPM 2026 probe reply, an XTGETTCAP `Sync` reply (value discarded; only support is recorded), and detection-time seeding from the `Sync` extended capability in the terminfo entry or a non-empty `TMUX` environment variable. Probe replies outrank seeded evidence in both directions, so a negative DECRPM reply turns the capability off even when detection seeded it.
#### Migration
`Capabilities` gains a required `syncOutput` field. Any object literal passed to `createTerm` as `terminfo.capabilities` must include it:
```diff
terminfo: {
capabilities: {
colors: 256,
trueColor: false,
bce: true,
autoMargin: true,
xenl: true,
altScreen: true,
styledUnderline: false,
+ syncOutput: false,
},
}
```
`createTermNative` now requires a `RenderCapabilities` argument as its third parameter:
```diff
- const native = await createTermNative(width, height);
+ const native = await createTermNative(width, height, { syncOutput: false });
```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 @@ | |||
| --- | |||
Contributor
There was a problem hiding this comment.
Changeset needs revision.
Changeset package scope does not match the affected packages confidently.
View the proposed replacement
---
'@bomb.sh/tty': minor
---
Adds synchronized output (DEC mode 2026) to full-screen rendering.
When `RuntimeCapabilities.syncOutput` is true, every full-screen frame is wrapped in Begin/End Synchronized Update (`CSI ? 2026 h` / `CSI ? 2026 l`) so the terminal presents the frame as one atomic repaint without tearing. No-op frames and line-mode output are never wrapped.
`Capabilities.syncOutput` is raised by three evidence sources, in precedence order: a DECRPM 2026 probe reply, an XTGETTCAP `Sync` reply (value discarded; only support is recorded), and detection-time seeding from the `Sync` extended capability in the terminfo entry or a non-empty `TMUX` environment variable. Probe replies outrank seeded evidence in both directions, so a negative DECRPM reply turns the capability off even when detection seeded it.
#### Migration
`Capabilities` gains a required `syncOutput` field. Any object literal passed to `createTerm` as `terminfo.capabilities` must include it:
```diff
terminfo: {
capabilities: {
colors: 256,
trueColor: false,
bce: true,
autoMargin: true,
xenl: true,
altScreen: true,
styledUnderline: false,
+ syncOutput: false,
},
}
```
`createTermNative` now requires a `RenderCapabilities` argument as its third parameter:
```diff
- const native = await createTermNative(width, height);
+ const native = await createTermNative(width, height, { syncOutput: false });
```
|
Size Increased — +1.6 KB 124.2 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, |
Collaborator
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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.
Capabilities were copied into reduce() on every render. The renderer now owns them: set_capabilities(ct, flags) stores a CAP_* bitfield on the Clayterm instance, and reduce() reads it from there. The host pushes flags at creation and again from term.update() only when a folded event changes them. init() zeroes instance state, so the native wrapper re-pushes after every re-init; a resize keeps the wrap.
input.h already defines CAP_SYNC_OUTPUT as a CapabilityEvent key (5). Any translation unit including both headers silently redefined it.
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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.