Struct ScrollState 

pub struct ScrollState {
    pub offset_x: i32,
    pub offset_y: i32,
    pub content_w: i32,
    pub content_h: i32,
    pub axis: ScrollAxis,
    pub snap: SnapConfig,
    pub snap_align: SnapAlign,
    pub scrollbar_mode: ScrollbarMode,
    pub snap_attraction_radius: i32,
}

Scroll metadata owned by a scrollable ObjectNode.

Attach via ObjectNode::set_scroll_state. The node’s SCROLLABLE flag is set automatically.

Content extent and viewport

The viewport size is derived from the node’s Widget::bounds() at the time of each scroll computation. The maximum scroll offset is:

max_scroll_y = (content_h - viewport_h).max(0)
max_scroll_x = (content_w - viewport_w).max(0)

LPAR-05 §5: SCROLLABLE is independent of actual overflow; the content extent is supplied explicitly (LPAR-10 will compute it from layout later).

Fields

offset_x: i32

Current horizontal scroll offset in logical pixels.

offset_y: i32

Current vertical scroll offset in logical pixels.

content_w: i32

Explicit content width in logical pixels.

The maximum horizontal scroll offset is (content_w - viewport_w).max(0).

content_h: i32

Explicit content height in logical pixels.

The maximum vertical scroll offset is (content_h - viewport_h).max(0).

axis: ScrollAxis

Scroll axis supported by this container.

snap: SnapConfig

Snap configuration.

snap_align: SnapAlign

Snap alignment (which viewport edge a snap point aligns to).

scrollbar_mode: ScrollbarMode

Scrollbar display mode.

snap_attraction_radius: i32

Snap attraction radius in pixels.

Implementations

impl ScrollState

pub fn new() -> Self

Create default scroll state for a vertical-only container.

Content extent must be updated via Self::content_w / Self::content_h before scroll is meaningful.

pub fn max_scroll_y(&self, viewport_h: i32) -> i32

Return the maximum allowed vertical scroll offset given a viewport height.

pub fn max_scroll_x(&self, viewport_w: i32) -> i32

Return the maximum allowed horizontal scroll offset given a viewport width.

pub fn set_offset_y(&mut self, new_y: i32, viewport_h: i32) -> bool

Clamp and set the vertical offset; returns true if it changed.

pub fn set_offset_x(&mut self, new_x: i32, viewport_w: i32) -> bool

Clamp and set the horizontal offset; returns true if it changed.

pub fn scrollbar_thumb(&self, viewport: Rect) -> Option<Rect>

Compute the vertical scrollbar thumb rect in screen space for the given viewport Rect, using the same formula as ScrollView::scrollbar_thumb() (widgets/src/scroll_view.rs lines 139–158).

Returns None when:

• scrollbar_mode is ScrollbarMode::Off, or
• the content does not overflow the viewport (content_h ≤ viewport.height).

The returned rect is positioned on the right edge of viewport with width SCROLLBAR_WIDTH and a gap of SCROLLBAR_MARGIN pixels. Thumb height is computed as:

thumb_h = (viewport_h² / content_h).clamp(SCROLLBAR_MIN_THUMB, viewport_h)

Thumb position reflects the current offset_y: at offset 0 the thumb sits at the top of the track; at max_scroll_y the thumb sits at the bottom.

Notes

• Rendering and Auto-mode visibility are the consuming widget’s responsibility. This method returns geometry only; whether the scrollbar is currently visible (e.g. during an active session in Auto mode) is managed by the caller.
• Horizontal axis is deferred (v1 vertical-first, LPAR-05 §17).

Trait Implementations

impl Clone for ScrollState

fn clone(&self) -> ScrollState

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ScrollState

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for ScrollState

fn default() -> Self

Returns the “default value” for a type.