Struct ScrollController 

pub struct ScrollController { /* private fields */ }

LPAR-05 scroll controller.

Consumes DragStart/DragMove/DragEnd events and tick advances to drive scroll offsets on ObjectNode-based scroll containers. Call process on every drag event and tick on every Event::Tick.

Determinism

Given identical (event, tick) input sequences, the controller produces identical emitted-event and offset sequences (LPAR-05 §8.1).

Thread safety

ScrollController is not Send or Sync. Use it from a single thread.

Implementations

impl ScrollController

pub fn new(config: ScrollConfig) -> Self

Create a new controller with the given configuration.

pub fn default_config() -> Self

Create a new controller with default configuration.

pub fn tick(&mut self, root: &mut ObjectNode, sink: &mut dyn FnMut(Rect))

Advance the internal tick counter and process any active throw/snap tween.

Call this once per Event::Tick. The sink callback receives each viewport dirty rect for every effective offset change.

pub fn process( &mut self, root: &mut ObjectNode, ev: &Event, sink: &mut dyn FnMut(Rect), )

Process a drag event (DragStart, DragMove, or DragEnd).

Pass the drag stream event from the DragRecognizer. Other events are silently ignored (use tick for Event::Tick).

The sink callback receives viewport dirty rects for every effective offset change.

pub fn is_active(&self) -> bool

Return true when a scroll session is currently active (between ScrollBegin and ScrollEnd, inclusive of the throw phase).

Use this from the platform layer to determine whether a drag event has been absorbed by the scroll controller so that it MUST NOT also be dispatched as a normal drag gesture (LPAR-05 §7.2).

pub fn cancel_if_active( &mut self, root: &mut ObjectNode, path: &[usize], sink: &mut dyn FnMut(Rect), )

Notify the controller that the container at path is being invalidated (detached, hidden, or SCROLLABLE cleared) during an active session.

If the active session targets that container, ScrollEnd is emitted before the structural change becomes visible (LPAR-05 §7.6). Call this before mutating the node.