Moving/Dragging
You can use BoxTransformer.move to translate a box by some amount of pixels.
final Box rect = Box.fromLTWH(50, 50, 100, 100);
final MoveResult result = BoxTransformer.move(
initialRect: rect,
initialLocalPosition: Vector2.zero(),
localPosition: Vector2.zero(),
);
result.position; // the new position of the box
BoxTransformer.move returns a MoveResult that contains information about the new position of the box.
result.position is a Vector2 that defines the new position of the box.
Limiting movements
You can limit the movements by providing clampingRect to BoxTransformer.move to limit the movements to a specific
area.
final Box rect = Box.fromLTWH(50, 50, 100, 100);
final MoveResult result = BoxTransformer.move(
initialRect: rect,
initialLocalPosition: Vector2.zero(),
localPosition: Vector2.zero(),
clampingRect: Box.fromLTWH(0, 0, 1000, 1000),
);
result.position; // the new position of the box
Moving a rotated box
BoxTransformer.move accepts rotation (radians) and bindingStrategy parameters. The solver computes the joint
feasible translation interval that keeps the rect inside the clamp under the active strategy and slides into it; if
the requested delta would push the box past the clamp, the result is clamped to the wall.
final MoveResult result = BoxTransformer.move(
initialRect: Box.fromLTWH(50, 50, 100, 100, rotation: 0.4),
initialLocalPosition: startCursor,
localPosition: currentCursor,
rotation: 0.4,
bindingStrategy: BindingStrategy.boundingBox,
clampingRect: clamp,
);
See Rotating and Binding Strategies for the rotation-specific semantics.