Module: ui.widgets.scrollview

Source: ./ui/widgets/scrollview.reef

Overview

ui/widgets/scrollview.reef - Scrollable container widget Part of reef-stdlib UI module

The ScrollView widget provides a scrollable view into content that may be larger than the visible area. It supports both horizontal and vertical scrolling with optional scrollbars.

ScrollView features:

Horizontal and/or vertical scrolling
Scrollbars (auto-hide, always visible, or never visible)
Smooth scrolling with momentum (optional)
Mouse wheel and keyboard navigation
Content clipping

Types

ScrollBarPolicy (enum)

Variants:

Auto
Always
Never

ScrollDirection (enum)

Variants:

Horizontal
Vertical
Both

Objects

ScrollView

Extends: widget.Widget

Fields:

Name	Type
`scroll_x`	`float`
`scroll_y`	`float`
`content_width`	`float`
`content_height`	`float`
`h_policy`	`ScrollBarPolicy`
`v_policy`	`ScrollBarPolicy`
`dragging_h`	`bool`
`dragging_v`	`bool`
`drag_start_x`	`float`
`drag_start_y`	`float`
`drag_start_scroll`	`float`
`h_hovered`	`bool`
`v_hovered`	`bool`

`proc init(id: widget.WidgetId)`

Methods:

`override shared fn kind(): string`

`exclusive proc set_scroll(x: float, y: float)`

`exclusive proc set_content_size(size: core.Size)`

`exclusive proc set_h_policy(policy: ScrollBarPolicy)`

`exclusive proc set_v_policy(policy: ScrollBarPolicy)`

`exclusive proc scroll_by(dx: float, dy: float)`

`exclusive proc scroll_to_top()`

`exclusive proc scroll_to_bottom()`

`exclusive proc scroll_to_left()`

`exclusive proc scroll_to_right()`

`shared fn clone(): ScrollView`

D2 (docs/design/2026-09-08-ui-modernization.md): a SHALLOW copy. Setters mutate the receiver (reef-lang#62), so "give me a variant and leave the original alone" has to be asked for explicitly. Referenced objects are shared, not deep-copied.

`shared fn preferred_size(content_size: core.Size): core.Size`

`exclusive proc layout(constraints: layout.Constraints)`

`override exclusive fn handle_event(e: event.Event): widget.EventResult`

`override exclusive proc paint(surf: surface.Surface, th: theme.Theme)`

Functions

`fn scrollbar_auto(): ScrollBarPolicy`

`fn scrollbar_always(): ScrollBarPolicy`

`fn scrollbar_never(): ScrollBarPolicy`

`fn is_scrollbar_auto(p: ScrollBarPolicy): bool`

`fn is_scrollbar_always(p: ScrollBarPolicy): bool`

`fn is_scrollbar_never(p: ScrollBarPolicy): bool`

`fn scroll_horizontal(): ScrollDirection`

`fn scroll_vertical(): ScrollDirection`

`fn scroll_both(): ScrollDirection`

`fn scrollview(): ScrollView`

`fn scrollview_with_policy(h_policy: ScrollBarPolicy, v_policy: ScrollBarPolicy): ScrollView`

`fn scrollview_content_size(sv: ScrollView): core.Size`

`fn scrollview_viewport_size(sv: ScrollView): core.Size`

`fn scrollview_can_scroll_h(sv: ScrollView): bool`

`fn scrollview_can_scroll_v(sv: ScrollView): bool`

`fn scrollview_needs_h_scrollbar(sv: ScrollView): bool`

`fn scrollview_needs_v_scrollbar(sv: ScrollView): bool`

`fn scrollview_content_bounds(sv: ScrollView): core.Rect`

`fn handle_mouse_event(sv: ScrollView, me: event.MouseEvent): widget.EventResult`

`fn handle_key_event(sv: ScrollView, ke: event.KeyEvent): widget.EventResult`

`fn get_scrollbar_thumb_color(hovered: bool, colors: theme.ThemeColors): core.Color`

`fn get_v_thumb_height(sv: ScrollView): float`

`fn get_h_thumb_width(sv: ScrollView): float`

`fn get_v_thumb_position(sv: ScrollView, track_height: float): float`

`fn get_h_thumb_position(sv: ScrollView, track_width: float): float`

`fn clamp_scroll_x(sv: ScrollView, x: float): float`

`fn clamp_scroll_y(sv: ScrollView, y: float): float`

Procedures

`proc start_v_drag(sv: ScrollView, mx: float, my: float)`

`proc start_h_drag(sv: ScrollView, mx: float, my: float)`

`proc end_drag(sv: ScrollView)`

`proc update_v_drag(sv: ScrollView, my: float)`

`proc update_h_drag(sv: ScrollView, mx: float)`

`proc update_hover(sv: ScrollView, h_hover: bool, v_hover: bool)`

`proc paint_vertical_scrollbar(sv: ScrollView, surf: surface.Surface, th: theme.Theme, x: float, y: float, w: float, h: float)`

`proc paint_horizontal_scrollbar(sv: ScrollView, surf: surface.Surface, th: theme.Theme, x: float, y: float, w: float, h: float)`

`proc draw_border(surf: surface.Surface, x: float, y: float, w: float, h: float, color: core.Color)`

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