ScrollBar class

An interactive scrollbar widget that reflects and adjusts scrolling state.

The scrollbar bounds are determined automatically by querying the associated DiscreteScrollController's viewportExtent (how much content is visible) and totalExtent (the complete virtual size of all items).

Interaction Modes

• Mouse Clicks and Dragging: Clicking or dragging along the scrollbar track recalculates the proportional offset and invokes DiscreteScrollController.scrollOffset updates, shifting the content view accordingly.

Example Usage

ScrollBar(
  controller: myScrollController,
  direction: LayoutDirection.vertical,
  thumbChar: '█',
  trackChar: '░',
);

Properties and Settings

Property	Type	Description
controller	DiscreteScrollController?	Scroll state controller.
direction	LayoutDirection	Visual orientation (vertical/horizontal).
trackStyle	Style	Style of the background scrollbar track.
thumbStyle	Style	Style of the draggable scrollbar thumb.
thumbChar	String	Character used to draw the slider thumb.
trackChar	String	Character used to draw the track background.

Inheritance

• Object
• Widget
• ScrollBar

Constructors

ScrollBar({DiscreteScrollController? controller, int? viewportHeight, int? totalItems, int? scrollOffset, void onScrollChanged(int newOffset)?, LayoutDirection direction = LayoutDirection.vertical, Style trackStyle = const Style(modifiers: Modifier.dim), Style thumbStyle = const Style(modifiers: Modifier.reverse), String thumbChar = '█', String trackChar = '░'})

Creates a ScrollBar widget.

Properties

controller → DiscreteScrollController?

The controller that manages the scrolling state.

final

direction → LayoutDirection

The visual orientation of the scrollbar.

final

hashCode → int

The hash code for this object.

no setter, inherited

key → Key?

The optional key for this widget.

final, inherited

onScrollChanged → void Function(int newOffset)?

Fallback callback invoked when the scroll offset changes.

final

runtimeType → Type

A representation of the runtime type of the object.

no setter, inherited

scrollOffset → int?

Fallback property for the current scroll offset.

final

thumbChar → String

The character used to render the thumb.

final

thumbStyle → Style

The visual style of the thumb indicator.

final

totalItems → int?

Fallback property for the total number of items.

final

trackChar → String

The character used to render the background track.

final

trackStyle → Style

The visual style of the background track.

final

viewportHeight → int?

Fallback property for the number of visible items.

final

Methods

createElement() → Element

Creates an Element to manage this widget's location in the tree.

inherited

getIntrinsicHeight(int width) → int

Computes the intrinsic height of this widget under the given width constraint.

inherited

handleMouseEvent(MouseEvent event, int localX, int localY) → void

Handles track clicks or dragging of the thumb to update the scroll offset.

noSuchMethod(Invocation invocation) → dynamic

Invoked when a nonexistent method or property is accessed.

inherited

render(Buffer buffer, Rect area) → void

Renders the widget onto the provided buffer within the specified area.

override

toString() → String

A string representation of this object.

inherited

Operators

operator ==(Object other) → bool

The equality operator.

inherited