Summary

The output buffer tracks pending rendering work at two levels:

• Cell.IsDirty for individual cells
• DirtyLines for rows that may contain pending dirty cells

Rows remain flagged in DirtyLines after their dirty cells have been written and cleared. Subsequent output passes then continue to scan those rows despite there being no cell-level work left.

Proposed optimization

Maintain the row-level dirty-state lifecycle alongside the existing cell-level lifecycle:

1. Clear DirtyLines[row] after all pending cells in that row have been processed.
2. Mark DirtyLines[row] whenever a drawing operation dirties a cell in that row.

This allows the output pass to skip rows with no pending changes while preserving correct rendering for text writes, fills, and other buffer updates.

Expected impact

A prototype benchmark using a warmed 340x65 buffer and a single-cell update measured:

The benchmark uses a no-I/O output backend, so it isolates framework overhead.

Acceptance criteria

• A row is skipped when it contains no pending dirty cells.
• A row becomes eligible for output whenever a drawing operation dirties one of its cells.
• Existing rendering behavior, including fills and wide-glyph handling, remains correct.
• Regression tests cover clearing a row after output and re-marking it after a subsequent update.

Alternatives considered

Recomputing row state from every cell during each output pass would avoid stale flags, but would retain the full-screen scan that the row-level optimization is intended to avoid.