SnapDelegate class abstract interface

Delegate interface for snap-to behavior during node drag operations.

Implement this interface to provide custom snapping logic, such as alignment guides, grid snapping, or magnetic snapping to other nodes.

Position Model

The snapping system uses two positions:

• position: The user's intended position (freeform, raw movement)
• visualPosition: The displayed position (snapped)

Snap delegates transform position → visualPosition. The delegate receives the intended position and returns the snapped visual position.

Usage

class MySnapDelegate implements SnapDelegate {
  @override
  SnapResult snapPosition({
    required Set<String> draggedNodeIds,
    required Offset intendedPosition,
    required Rect visibleBounds,
  }) {
    // Calculate snapped position
    final snapped = calculateSnap(intendedPosition);
    return SnapResult(
      position: snapped,
      snappingX: snapped.dx != intendedPosition.dx,
      snappingY: snapped.dy != intendedPosition.dy,
    );
  }

  @override
  void onDragStart(Set<String> nodeIds) {
    // Prepare for snapping
  }

  @override
  void onDragEnd() {
    // Clean up snap state
  }
}

Implementers

• GridSnapDelegate
• SnapDelegateChain
• SnapPlugin

Properties

hashCode → int

The hash code for this object.

no setter, inherited

runtimeType → Type

A representation of the runtime type of the object.

no setter, inherited

Methods

noSuchMethod(Invocation invocation) → dynamic

Invoked when a nonexistent method or property is accessed.

inherited

onDragEnd() → void

Called when the drag operation ends.

onDragStart(Set<String> nodeIds) → void

Called when a node drag operation starts.

snapPosition({required Set<String> draggedNodeIds, required Offset intendedPosition, required Rect visibleBounds}) → SnapResult

Calculate the snapped visual position from the intended position.

toString() → String

A string representation of this object.

inherited

Operators

operator ==(Object other) → bool

The equality operator.

inherited