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Text Input Policies ​

Shared text input policies keep eager Input widgets and file-backed VirtualInput widgets aligned where behavior is independent of storage size. Eager Input and InputModel are the behavioral oracle for accepted text interaction, focus, caret, and command semantics. When shared behavior differs, fix VirtualInput or the shared policy unless a lazy storage difference is explicitly documented.

VirtualInput must not become eager to gain parity. It keeps file-backed storage, viewport rows, byte anchors, bounded movement APIs, selection, save, and per-row rendering in the lazy stack.

Policy ownership ​

  • assets/lua/text-input-focus-policy.fnl owns focus request, focus/blur, active-input connection, text-state entry, disconnect normalization, and focus-visual updates for Input-like widgets.
  • assets/lua/text-input-caret-policy.fnl owns focus-gated caret visibility, normal/insert caret color, mode-dependent caret width, line-height and column-width resolution, and bounded caret height rules.
  • assets/lua/text-input-key-policy.fnl owns direct widget shortcuts that are valid outside the normal-command engine, currently save, copy, and page scrolling. It must not grow private normal-mode edit or navigation handling.
  • assets/lua/text-input-geometry.fnl owns storage-neutral pointer/local-point, row, column, row-y, and screen-point geometry math.
  • assets/lua/text-normal-commands.fnl owns normal-mode command semantics. Commands call assets/lua/text-editing-port.fnl, which adapts eager InputModel and lazy VirtualInput operations without exposing storage internals to command code.

Lazy boundaries ​

Shared policies do not own file-scale data access. VirtualInput and LazyTextBuffer own the lazy boundaries:

  • file-backed piece-table storage and save/conflict behavior;
  • sparse line anchors, byte offsets, and viewport row anchors;
  • bounded cursor movement and row/column-to-byte resolution;
  • selection/copy state for the file-backed widget;
  • viewport sizing, clipping, child Text row construction, and per-row rendering;
  • exact scan paths for commands that intentionally require document-wide knowledge.

Future policy changes should pass storage-specific data into shared helpers rather than materializing huge files into strings, eager InputModel instances, or whole-line caches.

Validation expectations ​

For future VirtualInput interaction changes, add or update file-backed lazy parity tests. Fixtures should force lazy paths with tiny chunks, narrow viewports, long rows, far horizontal scroll, or enough content to exercise bounded anchor discovery. Tests may compare against eager Input for safe small fixtures, but huge-file behavior must never be implemented or validated by loading the whole file into eager storage.

Use project-native validation in this order for Fennel-facing behavior: compile check, constraints, then focused input/virtual-input tests. Broader make test or E2E validation is appropriate when command routing, file viewer pointer routing, or central runtime behavior changes.