Model contracts

This section defines the minimal Core model contracts.

1) Row model

Base API:

• getSnapshot()
• getRow(index) / getRowsInRange(range)
• setViewportRange(range)
• setSortModel(model) / setFilterModel(model)
• setGroupBy(spec | null) / toggleGroup(groupKey)
• refresh(reason)

DataGridRowNode is required:

• kind: "leaf" | "group"
• rowKey (stable identity)
• sourceIndex / displayIndex
• groupMeta for groups
• state.selected/expanded/pinned

2) Column model

Canonical column fields: key, label, width, minWidth, maxWidth, visible, pin.

API:

• getSnapshot() / getColumn(key)
• setColumns(columns)
• setColumnOrder(keys)
• setColumnVisibility(key, visible)
• setColumnWidth(key, width)
• setColumnPin(key, pin)

3) Edit model

• getSnapshot()
• getEdit(rowId, columnKey)
• setEdit(patch) / setEdits(patches)
• clearEdit(rowId, columnKey) / clearAll()

4) GroupBy and TreeView

• GroupBy lives in the RowModel.
• Tree is a projection of group/leaf rows.
• Virtualization always consumes a flat stream.