Struct VirtualViewCallbackInfo 

pub struct VirtualViewCallbackInfo {
    pub reason: VirtualViewCallbackReason,
    pub system_fonts: *const FcFontCache,
    pub image_cache: *const ImageCache,
    pub window_theme: WindowTheme,
    pub window_frame: WindowFrame,
    pub bounds: HidpiAdjustedBounds,
    pub materialized: LogicalRect,
    pub virtual_rect: LogicalRect,
    pub scroll_offset: LogicalPosition,
    /* private fields */
}

Fields

reason: VirtualViewCallbackReason

system_fonts: *const FcFontCache

image_cache: *const ImageCache

window_theme: WindowTheme

window_frame: WindowFrame

The window’s CURRENT frame: normal, minimized, maximized, fullscreen.

Here for the same reason window_theme is: a view whose content depends on a window-level fact should read that fact, not be handed a copy of it at build time and then kept in sync. The window control that has to draw “maximize” or “restore” is the case - a seeded copy is wrong the moment the window manager maximizes the window itself (super+up, edge snap, a tiling rule), which never goes through the button’s own callback.

bounds: HidpiAdjustedBounds

RECT 1 - THE CONTAINER: the VirtualView’s on-screen box, computed by the framework from the outer DOM. You do not set this; you render into it.

materialized: LogicalRect

RECT 2 - WHAT IS CURRENTLY MATERIALIZED, in VIRTUAL space: the window you returned last time (origin = where it starts in the document, size = its extent). Zero-sized on the first invoke.

virtual_rect: LogicalRect

RECT 3 - THE DOCUMENT, in VIRTUAL space: the extent you last declared, which is what the scrollbar currently represents.

scroll_offset: LogicalPosition

WHERE THE USER IS LOOKING: the live scroll offset in virtual space.

This is the input your “which slice do I render?” math keys off. It was previously spelled virtual_scroll_offset and the engine hardcoded that to zero, so apps computing a page index from it always rendered the first page — one of the two reasons a VirtualView could not scroll.

Implementations

impl VirtualViewCallbackInfo

pub const fn new<'a>( reason: VirtualViewCallbackReason, system_fonts: &'a FcFontCache, image_cache: &'a ImageCache, window_theme: WindowTheme, window_frame: WindowFrame, bounds: HidpiAdjustedBounds, materialized: LogicalRect, virtual_rect: LogicalRect, scroll_offset: LogicalPosition, ) -> Self

pub const fn set_callable_ptr(&mut self, callable: &OptionRefAny)

Set the callable pointer for FFI language bindings

pub fn set_measure_dom_fn(&mut self, f: MeasureDomFn, ctx: *mut c_void)

Inject the headless-measure trampoline (called by the layout crate right before the user callback is invoked).

pub fn measure_dom(&self, dom: Dom, available: LogicalSize) -> LogicalSize

Measure a DOM headlessly: style + lay it out against available constraints using the host window’s fonts and system style, without touching the live layout. Returns the union of all node bounds.

Use a very tall available.height (e.g. 1_000_000.0) to obtain a DOM’s natural height at a fixed width - the building block for virtual-scroll sizing: measure one (or a few) item template(s), then virtual_scroll_size.height = item_height * item_count and render only the visible window of items. Each call is a full cold layout pass, so cache measured sizes per item template.

Returns LogicalSize::zero() when no measure hook was injected.

pub fn measure_dom_shrink_to_fit( &self, dom: Dom, bound: LogicalSize, ) -> LogicalSize

Measure a DOM headlessly at the size its CONTENT asks for: as wide as its max-content width (no wider than bound), and as tall as that makes it. The natural-size counterpart of Self::measure_dom, whose block root stretches to whatever width it is given - so a label measured that way reports the box, not the text.

This is what a content-sized view returns as its materialized rect: a text label, a badge, a popup panel. Pass a generous bound (a few thousand pixels) for “unconstrained”; the view is then laid out at the size it reports (a VirtualView with width: auto is sized by what it returns).

Returns LogicalSize::zero() when no measure hook was injected.

pub fn get_ctx(&self) -> OptionRefAny

Get the callable for FFI language bindings (Python, etc.)

pub const fn get_bounds(&self) -> HidpiAdjustedBounds

Trait Implementations

impl Clone for VirtualViewCallbackInfo

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 VirtualViewCallbackInfo

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

Formats the value using the given formatter.