Interface ICollisionProvider

Namespace

FlowGraph.Avalonia.Input

Assembly

FlowGraph.Avalonia.dll

Interface for providing collision detection and prevention during node drag operations. External systems (like collision managers) can implement this interface to prevent nodes from overlapping during drag without directly modifying node positions themselves.

public interface ICollisionProvider

Remarks

This follows the "single authority" pattern where the drag system remains the sole authority for setting node positions. Collision providers suggest offsets to prevent overlap, and the drag system applies them after snap offsets.

Semantic difference from ISnapProvider:

• Snap = attraction (guide lines pull nodes toward alignment)
• Collision = repulsion (prevents nodes from overlapping)

Methods

GetCollisionOffset(IReadOnlyList<Node>, Point)

Calculate an offset to prevent collision for nodes being dragged.

Point? GetCollisionOffset(IReadOnlyList<Node> nodes, Point proposedPosition)

Parameters

nodes IReadOnlyList<Node>

The nodes currently being dragged.

proposedPosition Point

The position the drag system is proposing for the primary node (after applying delta, grid snapping, and snap provider offset).

Returns

Point?

An offset to apply to prevent collision, or null if no collision would occur. The offset is relative to the proposed position.

OnDragEnd(IReadOnlyList<Node>, bool)

Called when a drag operation ends.

void OnDragEnd(IReadOnlyList<Node> nodes, bool cancelled)

Parameters

nodes IReadOnlyList<Node>

The nodes that were dragged.

cancelled bool

Whether the drag was cancelled.

OnDragStart(IReadOnlyList<Node>, Point)

Called when a drag operation starts.

void OnDragStart(IReadOnlyList<Node> nodes, Point startPosition)

Parameters

nodes IReadOnlyList<Node>

The nodes being dragged.

startPosition Point

The starting canvas position of the drag.