GridSheetSnapshot class

Immutable snapshot of grid state for undo/redo operations.

This class captures a complete snapshot of the grid's data and configuration at a specific point in time. It's used by undo/redo systems to save and restore grid state.

Captured State

The snapshot includes:

  • Data: All rows and columns with their current state
  • Sorting: Active sort keys and directions
  • Filtering: Applied filter criteria
  • Formatting: Conditional formatting rules
  • Pagination: Current page and page size

Usage Example

class GridUndoRedoManager {
  final List<GridSheetSnapshot> _undoStack = [];
  final List<GridSheetSnapshot> _redoStack = [];

  // Save current state before making changes
  void saveSnapshot(GridSheetManager manager) {
    final snapshot = GridSheetSnapshot(
      rows: List.from(manager.rows),
      columns: List.from(manager.columns),
      sortKeys: List.from(manager.sortKeys),
      filters: Map.from(manager.filters),
      conditionalFormatRules: List.from(manager.conditionalFormatRules),
      currentPage: manager.currentPage,
      rowsPerPage: manager.rowsPerPage,
    );

    _undoStack.add(snapshot);
    _redoStack.clear();  // Clear redo stack on new change
  }

  // Restore previous state
  void undo(GridSheetManager manager) {
    if (_undoStack.isEmpty) return;

    // Save current state to redo stack
    saveToRedoStack(manager);

    // Restore previous state
    final snapshot = _undoStack.removeLast();
    restoreSnapshot(manager, snapshot);
  }

  void redo(GridSheetManager manager) {
    if (_redoStack.isEmpty) return;

    // Save current state to undo stack
    saveSnapshot(manager);

    // Restore next state
    final snapshot = _redoStack.removeLast();
    restoreSnapshot(manager, snapshot);
  }

  void restoreSnapshot(GridSheetManager manager, GridSheetSnapshot snapshot) {
    manager.setRows(snapshot.rows);
    manager.setColumns(snapshot.columns);
    manager.setSortKeys(snapshot.sortKeys);
    manager.addFilters(snapshot.filters);
    manager.setConditionalFormatRules(snapshot.conditionalFormatRules);
    manager.goToPage(snapshot.currentPage);
    manager.changeRowsPerPage(snapshot.rowsPerPage);
  }
}

Deep Copy Considerations

The snapshot constructor performs shallow copies of collections. If you need true immutability with deep copies, consider:

GridSheetSnapshot createDeepCopy(GridSheetManager manager) {
  return GridSheetSnapshot(
    rows: manager.rows.map((r) => GridSheetRow(
      key: r.key,
      index: r.index,
      data: List.from(r.data),  // Deep copy data
      isSelected: r.isSelected,
      height: r.height,
      state: r.state,
    )).toList(),
    // ... similar deep copies for other fields
    columns: manager.columns.map((c) => c.copyWith()).toList(),
    sortKeys: manager.sortKeys.map((s) => s.copyWith()).toList(),
    filters: Map.from(manager.filters),
    conditionalFormatRules: manager.conditionalFormatRules
        .map((r) => r.copyWith()).toList(),
    currentPage: manager.currentPage,
    rowsPerPage: manager.rowsPerPage,
  );
}

Memory Considerations

Snapshots can consume significant memory for large grids. Consider:

  • Limiting undo/redo stack size
  • Implementing compression for old snapshots
  • Using delta-based undo (store changes, not full state)
  • Clearing history periodically or on save

See also:

Constructors

GridSheetSnapshot({required List<GridSheetRow> rows, required List<GridSheetColumn> columns, required List<GridSheetSortState> sortKeys, required Map<String, List> filters, required List<GridSheetConditionalFormatRule> conditionalFormatRules, required int currentPage, required int rowsPerPage})
Creates an immutable snapshot of grid state.
const

Properties

columns → List<GridSheetColumn>
All columns in the grid at snapshot time.
final
conditionalFormatRules → List<GridSheetConditionalFormatRule>
Conditional formatting rules at snapshot time.
final
currentPage → int
The current page number at snapshot time (1-based).
final
filters → Map<String, List>
Active filter criteria at snapshot time.
final
hashCode → int
The hash code for this object.
no setterinherited
rows → List<GridSheetRow>
All rows in the grid at snapshot time.
final
rowsPerPage → int
The rows per page setting at snapshot time.
final
runtimeType → Type
A representation of the runtime type of the object.
no setterinherited
sortKeys → List<GridSheetSortState>
Active sort keys at snapshot time.
final

Methods

copyWith({List<GridSheetRow>? rows, List<GridSheetColumn>? columns, List<GridSheetSortState>? sortKeys, Map<String, List>? filters, List<GridSheetConditionalFormatRule>? conditionalFormatRules, int? currentPage, int? rowsPerPage}) → GridSheetSnapshot
Creates a copy of this configuration with the given fields replaced.
noSuchMethod(Invocation invocation) → dynamic
Invoked when a nonexistent method or property is accessed.
inherited
toString() → String
A string representation of this object.
inherited

Operators

operator ==(Object other) → bool
The equality operator.
inherited