LayoutEngine class Layout

The engine responsible for measuring and positioning components in the terminal UI.

A LayoutEngine recursively measures components starting from the root ComponentInstance, assigns bounds, and produces a list of PositionedComponentInstances ready for rendering.

Responsibilities

• Measure components using their ComponentInstance.measure method.
• Apply layout direction (Axis.horizontal or Axis.vertical).
• Account for padding, gaps, and absolute positioning.
• Record which component renders each child.

Lifecycle

• Created by the application’s renderer before layout computation.
• compute is called to produce layout results.
• Internal _layoutRecursiveCompute is called recursively to measure and assign bounds to all child components.

See also

• ParentComponentInstance — For components that can contain children.
• PositionedComponentInstance — Holds final position data.
• Axis — Layout direction.
• Rect — Defines positions and sizes.

Example

final engine = LayoutEngine(
  rootInstance: myRoot,
  children: myRoot.childrenInstance,
  direction: Axis.vertical,
  bounds: Rect(x: 0, y: 0, width: 80, height: 24),
  childGap: 1,
);
final positioned = engine.compute(Size(width: 80, height: 24));

Constructors

LayoutEngine({required ComponentInstance rootInstance, required List<ComponentInstance> children, required Axis direction, required Rect bounds, int childGap = 0})

Creates a layout engine with the given configuration.

Properties

bounds → Rect

The total bounds available for layout.

final

childGap → int

Gap between children in the specified layout direction.

final

children → List<ComponentInstance>

Direct children of the root instance.

final

direction → Axis

Layout direction for children.

final

hashCode → int

The hash code for this object.

no setter, inherited

result → List<PositionedComponentInstance>

Stores the final positioned results after computation.

final

rootInstance → ComponentInstance

The root component in the layout hierarchy.

final

runtimeType → Type

A representation of the runtime type of the object.

no setter, inherited

Methods

compute(Size maxSize) → List<PositionedComponentInstance>

Computes the layout starting from rootInstance.

fitHeight() → int

Computes the total height needed to fit all children based on direction and childGap.

fitWidth() → int

Computes the total width needed to fit all children based on direction and childGap.

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