Class OverscaleCurtainRegionCache

Namespace: EncDotNet.S100.Renderers.Mapsui

Assembly: EncDotNet.S100.Renderers.Mapsui.dll

A memoising ComputeRegions(IReadOnlyList<OverscaleCellInput>, double) for a caller that recomputes the curtain on every zoom step over a mostly unchanged set of cells (issue #691).

public sealed class OverscaleCurtainRegionCache

Inheritance: object

OverscaleCurtainRegionCache

Inherited Members: object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.ReferenceEquals(object, object)

object.ToString()

Remarks

A cell's curtain region (its coverage minus every strictly-finer overlapping coverage) and its compilation resolution depend only on the cells, never on the viewport. Only the overscale factor, and so which cells get a region, depends on the resolution. This cache keeps the resolution-independent part per cell. A call with the same cells as the previous one re-evaluates the factors (cheap) and reuses every region it has already computed, instead of running the NetTopologySuite Intersects / Difference overlay for every overscaled cell against every finer cell again.

"The same cells" means the same count, and at each position a cell with the same Coverage instance, compilation-scale denominator and name. Anything else discards the cache, so the result is always what ComputeRegions(IReadOnlyList<OverscaleCellInput>, double) returns for the given cells and resolution. Regions are still computed lazily, the first time a cell is overscaled, so a cell that never is costs nothing.

Not thread-safe: use one instance per caller (the Viewer calls it on the UI thread).

Methods

ComputeRegions(IReadOnlyList<OverscaleCellInput>, double)

Computes the overscale-curtain regions for cells at viewportResolution, identical to ComputeRegions(IReadOnlyList<OverscaleCellInput>, double), reusing per-cell regions computed by earlier calls over the same cells.

public IReadOnlyList<OverscaleRegion> ComputeRegions(IReadOnlyList<OverscaleCellInput> cells, double viewportResolution)

Parameters

cells IReadOnlyList<OverscaleCellInput>: The loaded, drawing, scale-bearing cells.
viewportResolution double: The current viewport resolution in Web-Mercator metres per pixel (must be positive and finite; otherwise an empty list is returned).

Returns