SharpMap/Examples/ExampleCodeSnippets/ClipLabelPosition.cs at v1/main · SharpMap/SharpMap · GitHub

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namespace ExampleCodeSnippets

{

/// <summary>

/// A clipping utility that ensures every geometry is labeled within the current map viewport

/// </summary>

public class ClipLabelPosition

{

private GeoAPI.Geometries.IGeometry _clip;

private GeoAPI.Geometries.Prepared.IPreparedGeometry _prepClip;

/// <summary>

/// Creates an instance of this class

/// </summary>

/// <param name="map">A map</param>

public ClipLabelPosition(SharpMap.Map map)

{

map.MapViewOnChange += () =>

{

_clip = map.Factory.ToGeometry(map.Envelope);

_prepClip = NetTopologySuite.Geometries.Prepared.PreparedGeometryFactory.Prepare(_clip);

};

}

/// <summary>

/// A <see cref="SharpMap.Layers.LabelLayer.GetLocationMethod"/> implementation that clips

/// a feature's geometry to the current viewport of the map

/// </summary>

/// <param name="row">A feature</param>

/// <returns>A label position</returns>

public GeoAPI.Geometries.Coordinate GetClippedPosition(SharpMap.Data.FeatureDataRow row)

{

var g = _prepClip.Contains(row.Geometry)

? row.Geometry

: _clip.Intersection(row.Geometry);

return g.InteriorPoint.Coordinate;

}