Struct MapTileCache 

pub struct MapTileCache {
    pub layer: MapTileLayer,
    pub viewport: MapViewport,
    pub tiles: BTreeMap<MapTileId, TileEntry>,
    pub fetch_callback: Option<ThreadCallback>,
    pub drag_anchor: Option<LogicalPosition>,
    pub pinch_anchor: Option<f32>,
    pub on_viewport_changed: OptionMapViewportChanged,
    pub press_origin: Option<LogicalPosition>,
    pub on_pin_tap: OptionMapPinTap,
}

Fields

layer: MapTileLayer

viewport: MapViewport

tiles: BTreeMap<MapTileId, TileEntry>

Ready(svg) once the tile has been fetched + decoded; Pending while queued, Fetching while a worker thread is in flight; absent otherwise. BTreeMap for deterministic iteration so the debug log + e2e snapshots are stable.

fetch_callback: Option<ThreadCallback>

Worker thread entry point that fetches + decodes one tile. Supplied by MapWidget::dom_with_fetch (the caller, usually azul_dll’s map-tiles glue, provides this because the MVT decoder lives in azul-dll, which azul-layout can’t depend on). None means “no fetch wired”: tiles stay Pending and the placeholder grid renders. The merge callback carries this across relayout. Held as the ThreadCallback wrapper (not the raw fn pointer) so it round-trips through the FFI codegen.

drag_anchor: Option<LogicalPosition>

Pixel coordinates of the cursor at the last mouse-down / touch-down on the widget. Some while a drag is in flight, None between drags. The framework consults this on every mouse-move to derive the pixel delta, which then converts to a lat/lon delta via the Web Mercator inverse.

pinch_anchor: Option<f32>

Pinch reference distance (pixels) — the two-finger separation the last time a pinch event was observed for this widget. Some while a pinch is in flight, None between gestures. On each subsequent pinch update we compute dz = log2(current_distance / pinch_anchor) and add it to viewport.zoom, then reset the anchor to the current distance — so the gesture stays continuous across many frames.

on_viewport_changed: OptionMapViewportChanged

The user’s on_viewport_changed hook, copied here from the builder so the pan / pinch callbacks can fire it. Carried across relayout.

press_origin: Option<LogicalPosition>

Pixel position of the last pointer-down (the original press point, not overwritten by pan moves). Used to tell a tap from a drag in pointer-up.

on_pin_tap: OptionMapPinTap

The user’s on_pin_tap hook, copied from the builder so pointer-up can fire it. Carried across relayout.

Implementations

impl MapTileCache

pub fn new(layer: MapTileLayer, viewport: MapViewport) -> Self

pub fn mark_tile_ready(&mut self, tile: MapTileId, svg: AzString)

Worker-thread → main-thread write path. Set the decoded SVG for a tile (called from map_tile_writeback). Stamps Ready.

pub fn mark_tile_failed(&mut self, tile: MapTileId, error: AzString)

Mark a tile’s fetch as failed so the grid doesn’t re-spawn it every frame.

Trait Implementations

impl Debug for MapTileCache

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

Formats the value using the given formatter.