Struct SliverConstraints 

pub struct SliverConstraints {
    pub axis: ScrollAxis,
    pub scroll_offset: f64,
    pub preceding_scroll_extent: f64,
    pub overlap: f64,
    pub remaining_paint_extent: f64,
    pub cross_axis_extent: f64,
    pub viewport_main_axis_extent: f64,
    pub cache_origin: f64,
    pub remaining_cache_extent: f64,
    pub user_scroll_direction: ScrollDirection,
}

The sliver protocol a scrolling viewport lays its children out with — a widget implements SliverWidget and overrides Widget::as_sliver to answer SliverConstraints with a SliverGeometry; a viewport lays such a child out through ChildPod::layout_sliver_child. Lifted so an app’s own sliver needs no direct frust-core dependency. What a viewport hands each sliver child: its position in the scroll and the space left to fill — Flutter’s SliverConstraints.

All extents are logical pixels along axis unless named cross_axis_*. PartialEq is what ChildPod::layout_sliver_child’s layout skip compares, so constraints carrying a NaN never compare equal and always lay out again.

Fields

axis: ScrollAxis

The axis the viewport scrolls along (Flutter’s axis, derived there from axisDirection).

scroll_offset: f64

How far into this sliver the viewport’s leading edge has scrolled: 0 while the sliver’s start is on screen or ahead of it (Flutter’s scrollOffset).

preceding_scroll_extent: f64

The scroll extent consumed by every sliver before this one (Flutter’s precedingScrollExtent); may be infinite after an unbounded sliver.

overlap: f64

How many pixels from this sliver’s paint start an earlier sliver has already painted over, e.g. a pinned header (Flutter’s overlap).

remaining_paint_extent: f64

How many pixels of content the sliver should consider providing — the viewport’s paint space not yet taken by earlier slivers (Flutter’s remainingPaintExtent); may be infinite for a shrink-wrapping viewport.

cross_axis_extent: f64

The viewport’s extent across the scroll axis (Flutter’s crossAxisExtent).

viewport_main_axis_extent: f64

The viewport’s extent along the scroll axis (Flutter’s viewportMainAxisExtent).

cache_origin: f64

Where the cache area starts relative to scroll_offset, never positive (Flutter’s cacheOrigin).

remaining_cache_extent: f64

How much content the sliver should provide starting at cache_origin, visible region plus cache area (Flutter’s remainingCacheExtent).

user_scroll_direction: ScrollDirection

The direction the user is scrolling in (Flutter’s userScrollDirection).

Implementations

impl SliverConstraints

pub fn growth_direction(&self) -> GrowthDirection

Which way content grows — always GrowthDirection::Forward (Flutter’s growthDirection).

pub fn as_box_constraints(&self) -> BoxConstraints

Box constraints for a box child laid out inside this sliver: tight to cross_axis_extent across the axis, unbounded along it (Flutter’s asBoxConstraints() with its default extents).

pub fn debug_assert_valid(&self)

Debug-assert the constraints are well formed — Flutter’s SliverConstraints.debugAssertIsValid (including isNormalized).

Checks that scroll_offset, cross_axis_extent, viewport_main_axis_extent, remaining_paint_extent and remaining_cache_extent are non-negative (NaN fails), that cache_origin is not positive, and that preceding_scroll_extent and overlap are not NaN. Compiles to nothing without debug_assertions.

Trait Implementations

impl Clone for SliverConstraints

fn clone(&self) -> SliverConstraints

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for SliverConstraints

impl Debug for SliverConstraints

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

Formats the value using the given formatter.

impl PartialEq for SliverConstraints

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for SliverConstraints