Instruction file imported from openmarketdata/qpad3 (.github/instructions/viewer.instructions.md). Copyright stays with the author.

REPL Viewer — src/viewer.mjs

Readonly CodeMirror 6 instance that displays q input/output with gutter markers.

Conventions

• Uses StateField + StateEffect (addPrompt / clearPrompts) with RangeSet for per-line gutter markers — follow this pattern for any new marker types.
• PromptMarker subclass of GutterMarker renders q) (input) and => (output) markers.
• Auto-trims to last 16 q) calls and 64 => results via trimToFit().
• Theme is viewerTheme, defined inline — dark theme consistent with the editor.
• Shares qLanguage + qHighlightStyle from lang-q.mjs.

When Modifying

Adding a new display format

1. Extend viewer.disp() to handle the new prompt type.
2. Add a new GutterMarker subclass following the PromptMarker pattern.
3. Register the new marker in the gutter's StateField if needed.

Adding visual panel tabs (future)

• The right pane (div.two) will host tabs: REPL, Chart, Grid.
• Viewer remains the REPL tab; new panels mount alongside in the same container.
• Tab switching should preserve viewer scroll position and state.