Struct ScrollHandle 

pub struct ScrollHandle(/* private fields */);

A handle to the scroll state of an element, used to read the scroll position and to scroll it.

Create it with ScrollHandle::new, attach it with StatefulInteractiveElement::track_scroll, and keep it across renders, since the scroll state lives in the handle. Clones of a handle share the same state.

Example

let handle = ScrollHandle::new();
assert_eq!(handle.offset(), point(px(0.), px(0.)));
assert_eq!(handle.children_count(), 0);

Implementations

impl ScrollHandle

pub fn new() -> Self

Creates a new scroll handle with no scroll state. The offset is zero until an element is tracked with it.

pub fn offset(&self) -> Point<Pixels>

Returns the current scroll offset.

The offset is the distance from the top left of the scrolling element to the top left of its content. It is zero at the top and becomes more negative as the content scrolls up or to the left.

pub fn max_offset(&self) -> Point<Pixels>

Returns the largest offset the element can scroll to. The values are the distances the content can move, as positive values.

pub fn top_item(&self) -> usize

Returns the index of the first child that is at least partly visible at the top of the viewport.

Returns 0 if the element has no children.

pub fn bottom_item(&self) -> usize

Returns the index of the last child that is at least partly visible at the bottom of the viewport.

Returns 0 if the element has no children.

pub fn bounds(&self) -> Bounds<Pixels>

Returns the bounds of the scrolling element’s viewport, in window coordinates.

pub fn bounds_for_item(&self, ix: usize) -> Option<Bounds<Pixels>>

Returns the bounds of the child at ix, in window coordinates, or None if there is no such child.

pub fn scroll_to_item(&self, ix: usize)

Scrolls the smallest amount that makes the child at ix fully visible.

The scroll happens during the next prepaint. If the element is not scrollable on the axis, nothing happens.

pub fn scroll_to_top_of_item(&self, ix: usize)

Scrolls so that the child at ix is at the top of the viewport.

The scroll happens during the next prepaint.

pub fn scroll_to_bottom(&self)

Scrolls to the bottom of the content on the next prepaint.

pub fn set_offset(&self, position: Point<Pixels>)

Sets the scroll offset directly.

The offset is the distance from the top left of the scrolling element to the top left of its content, so scrolling down makes the offset more negative. Values outside the scrollable range are clamped during the next prepaint.

pub fn logical_scroll_top(&self) -> (usize, Pixels)

Returns the child at the top of the viewport, and how far its top edge is above the viewport’s top edge.

Use the pair to restore the same scroll position after the children change: scroll to the index, then offset by the pixels.

pub fn logical_scroll_bottom(&self) -> (usize, Pixels)

Returns the child at the bottom of the viewport, and how far its bottom edge is below the viewport’s bottom edge.

pub fn children_count(&self) -> usize

Returns the number of children that were laid out in the most recent frame.

Trait Implementations

impl Clone for ScrollHandle

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for ScrollHandle

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

Formats the value using the given formatter.

impl Default for ScrollHandle

fn default() -> Self

Returns the “default value” for a type.