Summary

• allow pager.layout and pager.position to be configured as layout-time callbacks
• evaluate both callbacks after dynamic maxRow / maxCol have been resolved
• expose rect, resolved orient, legend id, maxRow, and maxCol through a shared callback context
• preserve existing static string configurations and scrollbar behavior
• document the callback API in English and Chinese

Motivation

Multi-row discrete legends may need vertically arranged pager handlers aligned to the first row, while single-row legends should retain a horizontal, centered pager. Resolving these values during layout lets the pager follow responsive row and column counts.

Validation

• discrete legend callback unit coverage for dynamic and static layout / position
• verified callback order after maxRow / maxCol resolution
• verified resize transitions between single-row and multi-row results
• verified generated CJS, ESM, and public TypeScript declarations
• downstream split-render acceptance completed with a real multi-row legend