Struct VirtualScrollView 

pub struct VirtualScrollView<D, B: Fn(usize, &D) -> Element> { /* private fields */ }

One-direction scrollable area that dynamically builds and renders items based in their size and current available size, this is intended for apps using large sets of data that need good performance.

Unlike ScrollView, which lays out every child even when it is off screen, a VirtualScrollView takes a builder closure and only calls it for the items that are actually visible, so the cost stays roughly constant no matter how long the list is.

It needs two things to know which items fall inside the viewport: item_size, the fixed size of each item along the scroll axis, and length, the total number of items.

Example

fn app() -> impl IntoElement {
    rect().child(
        VirtualScrollView::new(|i, _| {
            rect()
                .key(i)
                .height(Size::px(25.))
                .padding(4.)
                .child(format!("Item {i}"))
                .into()
        })
        .length(300usize)
        .item_size(25.),
    )
}

Preview

Implementations

impl<B: Fn(usize, &()) -> Element> VirtualScrollView<(), B>

pub fn new(builder: B) -> Self

Creates a virtual scroll view that builds each item on demand from its index.

pub fn new_controlled(builder: B, scroll_controller: ScrollController) -> Self

Like new but driven by the given ScrollController.

impl<D, B: Fn(usize, &D) -> Element> VirtualScrollView<D, B>

pub fn new_with_data(builder_data: D, builder: B) -> Self

Like new but passes shared builder_data to every item build.

The builder closure cannot be compared across renders, so data captured inside it never triggers a rebuild. Passing the data here instead makes it part of the view’s PartialEq, so the visible items are rebuilt whenever it changes.

fn app() -> impl IntoElement {
    let items = use_state(|| vec!["a".to_string(), "b".to_string(), "c".to_string()]);

    // The current items are passed as data, so editing `items` rebuilds the visible rows.
    VirtualScrollView::new_with_data(items.read().clone(), |i, items: &Vec<String>| {
        rect()
            .key(i)
            .height(Size::px(25.))
            .child(items[i].clone())
            .into()
    })
    .length(items.read().len())
    .item_size(25.)
}

pub fn new_with_data_controlled( builder_data: D, builder: B, scroll_controller: ScrollController, ) -> Self

Like new_with_data but driven by the given ScrollController.

pub fn show_scrollbar(self, show_scrollbar: bool) -> Self

Toggles whether the scrollbar is shown when the content overflows.

pub fn direction(self, direction: Direction) -> Self

Sets the axis the items flow and scroll in.

pub fn scroll_with_arrows(self, scroll_with_arrows: impl Into<bool>) -> Self

Toggles whether the arrow keys scroll the view while it is focused.

pub fn item_size(self, item_size: impl Into<f32>) -> Self

Sets the fixed size of every item along the scroll axis, used to decide which items to render.

pub fn length(self, length: impl Into<usize>) -> Self

Sets the total number of items the view can scroll through.

pub fn invert_scroll_wheel(self, invert_scroll_wheel: impl Into<bool>) -> Self

Inverts the direction of the mouse wheel relative to the content.

pub fn drag_scrolling(self, drag_scrolling: bool) -> Self

Toggles scrolling by dragging the content, useful mainly for touch input.

pub fn scroll_controller( self, scroll_controller: impl Into<Option<ScrollController>>, ) -> Self

Attaches a ScrollController to drive this view externally.

pub fn max_width(self, max_width: impl Into<Size>) -> Self

Caps the width of the scroll view.

pub fn max_height(self, max_height: impl Into<Size>) -> Self

Caps the height of the scroll view.

Trait Implementations

impl<D: Clone, B: Clone + Fn(usize, &D) -> Element> Clone for VirtualScrollView<D, B>

fn clone(&self) -> VirtualScrollView<D, B>

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<D: PartialEq + 'static, B: Fn(usize, &D) -> Element + 'static> Component for VirtualScrollView<D, B>

fn render(self: &VirtualScrollView<D, B>) -> impl IntoElement

fn render_key(&self) -> DiffKey

impl<D: PartialEq, B: Fn(usize, &D) -> Element> ContainerSizeExt for VirtualScrollView<D, B>

fn width(self, width: impl Into<Size>) -> Self

Set the element’s width. See [Size].

fn height(self, height: impl Into<Size>) -> Self

Set the element’s height. See [Size].

fn expanded(self) -> Self

Expand both width and height using [Size::fill()].

impl<D: PartialEq, B: Fn(usize, &D) -> Element> KeyExt for VirtualScrollView<D, B>

fn write_key(&mut self) -> &mut DiffKey

Returns a mutable reference to the element’s diff key.

fn key(self, key: impl Hash) -> Self

Assign a key derived from any hashable value, used to reconcile elements in dynamic lists.

impl<D: PartialEq, B: Fn(usize, &D) -> Element> LayoutExt for VirtualScrollView<D, B>

fn get_layout(&mut self) -> &mut LayoutData

Returns a mutable reference to the element’s layout data.

fn layout(self, layout: LayoutData) -> Self

Replace all of the element’s layout data at once. See [LayoutData].

impl<D: PartialEq, B: Fn(usize, &D) -> Element> PartialEq for VirtualScrollView<D, B>

fn eq(&self, other: &Self) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.