Document actual default for ITerminalOptions.scrollback #174

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1. ThomasK33

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   on Jun 26, 2026
2. ThomasK33 commented on Jun 26, 2026

   

   ThomasK33

   on Jun 26, 2026

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   1. Classification — documentation; no outcome label. The reported mismatch is reproducible by static inspection, so status:could-not-reproduce is not applicable.

   2. Summary — The issue reports that the public ITerminalOptions.scrollback comment documents Default: 1000, while the Terminal constructor currently defaults options.scrollback to 10000. That is a small API documentation/default consistency problem, separate from the runtime scrollback byte/line issue tracked elsewhere.

   3. Evidence / reproduction — I read the full issue thread for Document actual default for ITerminalOptions.scrollback #174 (no comments at triage time), the related getViewport() returns corrupted data when viewport spans multiple pages #139 discussion, adjacent scrollbackLimit is documented as lines but interpreted as bytes by WASM #140, and the scrollback-related PRs called out below. The mismatch reproduces on the current checkout (6a1a50d) with a targeted grep:

      rg -n "scrollback\?: number|scrollback: options\.scrollback \?\? 10000|scrollbackLimit\?: number|scrollback_limit: number" lib/interfaces.ts lib/terminal.ts lib/types.ts

      lib/types.ts:535:  scrollbackLimit?: number;
      lib/types.ts:607:  scrollback_limit: number; // Number of scrollback lines (default: 10,000)
      lib/interfaces.ts:13:  scrollback?: number; // Default: 1000
      lib/terminal.ts:147:      scrollback: options.scrollback ?? 10000,
      

      The lines directly relevant to this issue are:

      // lib/interfaces.ts
      scrollback?: number; // Default: 1000
      
      // lib/terminal.ts
      scrollback: options.scrollback ?? 10000,

   4. Candidate fixes checked — No PR directly references Document actual default for ITerminalOptions.scrollback #174 yet.

      • docs: correct GhosttyTerminalConfig.scrollbackLimit docs #151 (docs: correct GhosttyTerminalConfig.scrollbackLimit docs) is open and only changes low-level lib/types.ts documentation for GhosttyTerminalConfig.scrollbackLimit / TerminalConfig.scrollback_limit. Its body explicitly notes that ITerminalOptions.scrollback remains misleading, so it does not resolve this issue.
      • docs(types): correct scrollbackLimit field documentation #168 (docs(types): correct scrollbackLimit field documentation) is closed and makes the same low-level docs change plus unrelated ignore-file changes; it does not touch lib/interfaces.ts or lib/terminal.ts.
      • fix: use cached row pins for WASM viewport rendering #133 (fix: use cached row pins for WASM viewport rendering) is the candidate fix for getViewport() returns corrupted data when viewport spans multiple pages #139. Its diff touches lib/ghostty.ts, WASM patch code, and regression tests; it converts scrollback line counts to bytes in the WASM path but does not update the ITerminalOptions.scrollback default comment, so it is not a direct fix for this documentation mismatch.

   5. Relevant code / likely cause — lib/interfaces.ts appears to have kept an xterm.js-shaped scrollback default comment (1000), while lib/terminal.ts intentionally constructs baseOptions.scrollback with options.scrollback ?? 10000. The neighboring low-level comments in lib/types.ts are also under active discussion in scrollbackLimit is documented as lines but interpreted as bytes by WASM #140/docs: correct GhosttyTerminalConfig.scrollbackLimit docs #151, but the exact mismatch reported here is the public ITerminalOptions comment versus the constructor default.

   6. Recommendation — Keep this open as a documentation cleanup. The smallest safe implementation is to update lib/interfaces.ts so ITerminalOptions.scrollback documents the actual 10000 default. If maintainers instead want xterm.js-compatible 1000 behavior, the constructor default and tests should be changed intentionally rather than only editing the comment. When scrollbackLimit is documented as lines but interpreted as bytes by WASM #140/fix: use cached row pins for WASM viewport rendering #133 is resolved, consider wording the scrollback docs so both the default and unit semantics remain clear.

   7. Adjacent issues — Existing scrollbackLimit is documented as lines but interpreted as bytes by WASM #140 tracks the larger scrollbackLimit line-count-vs-byte mismatch, and getViewport() returns corrupted data when viewport spans multiple pages #139 tracks viewport corruption that can be exacerbated by that runtime mismatch. I did not find another open or closed issue specifically for the ITerminalOptions.scrollback default comment, and no new adjacent issue was created.
3. ThomasK33

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   needs-triageIssue should be considered by the Mux triage loopIssue should be considered by the Mux triage loop

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   on Jun 26, 2026
4. ThomasK33

   closed this as completedin #178on Jun 26, 2026