ComponentInstance class abstract Components Core

The runtime representation of a Component in a layout or rendering process.

A ComponentInstance is created from a Component and is responsible for:

• Tracking layout bounds
• Measuring its required size
• Rendering itself to a CanvasBuffer

Unlike a Component, which is an immutable configuration object, a ComponentInstance holds mutable state such as _bounds and is tied to a specific rendering pass.

Subclasses must implement:

• measure to report the component’s desired size
• fitWidth and fitHeight for layout constraints
• render to draw the component on the screen

Example:

class MyButtonInstance extends ComponentInstance {
  @override
  Size measure(Size maxSize) {
    // Determine size based on content
  }

  @override
  int fitWidth() => 10;

  @override
  int fitHeight() => 3;

  @override
  void render(CanvasBuffer buffer, Rect bounds) {
    // Draw the button
  }
}

See also:

• Component for the immutable configuration counterpart
• EdgeInsets for padding
• Position for placement
• Rect and Size for layout geometry

Implementers

• InteractableComponentInstance
• ParentComponentInstance

Constructors

ComponentInstance.new({EdgeInsets padding = const EdgeInsets.all(0), Position position = const Position(x: 0, y: 0, positionType: PositionType.relative)})

Creates a ComponentInstance with optional padding and position.

Properties

bounds ↔ Rect

The current layout bounds for this component instance.

getter/setter pair

hashCode → int

The hash code for this object.

no setter, inherited

padding → EdgeInsets

The padding inside the component’s allocated space.

final

position → Position

The position of this component relative to its parent or container.

final

runtimeType → Type

A representation of the runtime type of the object.

no setter, inherited

Methods

fitHeight() → int

Returns the height this component should occupy based on its content or layout rules.

fitWidth() → int

Returns the width this component should occupy based on its content or layout rules.

measure(Size maxSize) → Size

Measures the size this component would like to occupy, given a maximum available size.

noSuchMethod(Invocation invocation) → dynamic

Invoked when a nonexistent method or property is accessed.

inherited

render(CanvasBuffer buffer, Rect bounds) → void

Renders the component into the provided CanvasBuffer using the given bounds as the drawing area.

toString() → String

A string representation of this object.

inherited

Operators

operator ==(Object other) → bool

The equality operator.

inherited