Class LayerAsync

Namespace

ThinkGeo.Core.Async

Assembly

ThinkGeo.Core.dll

This class is the base class for all types of Layers.

public abstract class LayerAsync : Layer

Inheritance

object

Layer

LayerAsync

Derived

WebBasedLayer

MbTilesLayer

MbTilesRasterLayer

Inherited Members

Layer.CloneDeep()

Layer.CloneDeepCore()

Layer.LoadLayer(Uri)

Layer.LoadLayer(Stream)

Layer.Open()

Layer.Close()

Layer.GetBoundingBox()

Layer.GetBoundingBoxCore()

Layer.Draw(GeoCanvas, Collection<SimpleCandidate>)

Layer.DrawWithColorTransformation(GeoCanvas, Collection<SimpleCandidate>, RectangleShape, float, float)

Layer.DrawException(GeoCanvas, Exception)

Layer.DrawExceptionCore(GeoCanvas, Exception)

Layer.OnDrawingException(DrawingExceptionLayerEventArgs)

Layer.OnDrawnException(DrawnExceptionLayerEventArgs)

Layer.IsDrawingNeeded(double)

Layer.IsDrawingNeededCore(double)

Layer.DrawAttributionCore(GeoCanvas, string)

Layer.OnDrawingAttribution(DrawingAttributionLayerEventArgs)

Layer.OnDrawnAttribution(DrawnAttributionLayerEventArgs)

Layer.OnDrawingProgressChanged(DrawingProgressChangedEventArgs)

Layer.RequestDrawing()

Layer.RequestDrawing(RectangleShape)

Layer.RequestDrawing(IEnumerable<RectangleShape>)

Layer.RequestDrawing(TimeSpan)

Layer.RequestDrawing(TimeSpan, RequestDrawingBufferTimeType)

Layer.RequestDrawing(RectangleShape, TimeSpan)

Layer.RequestDrawing(RectangleShape, TimeSpan, RequestDrawingBufferTimeType)

Layer.RequestDrawing(IEnumerable<RectangleShape>, TimeSpan)

Layer.RequestDrawing(IEnumerable<RectangleShape>, TimeSpan, RequestDrawingBufferTimeType)

Layer.StartRequestDrawing()

Layer.OnRequestedDrawing(RequestedDrawingLayerEventArgs)

Layer.OnRequestingDrawing(RequestingDrawingLayerEventArgs)

Layer.IsOpen

Layer.HasBoundingBox

Layer.IsOpenCore

Layer.DrawingTime

Layer.Name

Layer.Attribution

Layer.IsVisible

Layer.Transparency

Layer.BlueTranslation

Layer.RedTranslation

Layer.GreenTranslation

Layer.KeyColors

Layer.IsNegative

Layer.IsGrayscale

Layer.ColorMappings

Layer.DrawingExceptionMode

Layer.ThreadSafe

Layer.Projection

Layer.Background

Layer.WrappingMode

Layer.WrappingExtent

Layer.RequestDrawingInterval

Layer.DrawingProgressChanged

Layer.DrawingException

Layer.DrawnException

Layer.DrawingAttribution

Layer.DrawnAttribution

Layer.RequestedDrawing

Layer.RequestingDrawing

object.GetType()

object.MemberwiseClone()

object.ToString()

object.Equals(object)

object.Equals(object, object)

object.ReferenceEquals(object, object)

object.GetHashCode()

Remarks

The Layer class is where all other types of layers are inherited from. It provides the base set of functionality. Though all Layers inherit from this class, we strongly suggest if you decide to create your own layer type that you consider inheriting from the higher level RasterLayer for image-based layers and FeatureLayer for feature-based layers. They provide a rich set of default operations for the various types of layers and are simple to inherit from.

As it is abstract, there are a number of methods you need to implement. The first is DrawCore. In this method, you are responsible for drawing the layer's representation. The other two required methods are OpenCore and CloseCore. These open and close the Layer. In the Open, you are responsible for getting the layer ready for drawing. You should open any file references, etc. In the Close, you need to clean up all file handles, close other objects etc. It is important that the Close puts the class in a state where it can be re-opened in the future. It is different than Dispose, as closed Layers will still exist and can be re-opened later in the mapping life cycle. Many methods (in the layer and in higher level objects) will require that the Layer be open before these methods are called, otherwise they will throw an exception.

Constructors

LayerAsync()

This is the default constructor for the Layer.

protected LayerAsync()

Remarks

None

Methods

CloseAsync(CancellationToken)

This method closes the Layer and releases any resources it was using.

public Task CloseAsync(CancellationToken cancellationToken = default)

Parameters

cancellationToken CancellationToken

Returns

Task

None

Remarks

This abstract method is called from the concrete public method Close. The close method plays an important role in the life cycle of the Layer. It may be called after drawing to release any memory and other resources that were allocated since the Open method was called.

If you override this method, it is recommended that you take the following things into account: This method may be called multiple times, so we suggest you write the method so that that a call to a closed Layer is ignored and does not generate an error. We also suggest that in the Close you free all resources that have been opened. Remember that the object will not be destroyed, but will be re-opened possibly in the near future.

CloseAsyncCore(CancellationToken)

protected virtual Task CloseAsyncCore(CancellationToken cancellationToken)

Parameters

cancellationToken CancellationToken

Returns

Task

CloseCore()

[Obsolete("Please use its async version instead for better efficiency and responsiveness. This sync version will no longer be available after 13.3.")]
protected override void CloseCore()

DrawAsync(GeoCanvas, Collection<SimpleCandidate>)

This method draws the Layer.

public Task DrawAsync(GeoCanvas canvas, Collection<SimpleCandidate> labelsInAllLayers)

Parameters

canvas GeoCanvas

This parameter is the view object or a NativeImage to draw on.

labelsInAllLayers Collection<SimpleCandidate>

This parameter represents the labels used for collision detection and duplication checking.

Returns

Task

None

Remarks

This method is the concrete wrapper for the abstract method DrawCore. This method draws the representation of the layer based on the extent you provided.

As this is a concrete public method that wraps a Core method, we reserve the right to add events and other logic to pre- or post-process data returned by the Core version of the method. In this way, we leave our framework open on our end, but also allow you the developer to extend our logic to suit your needs. If you have questions about this, please contact our support team as we would be happy to work with you on extending our framework.

Exceptions

ArgumentNullException

If you pass a null as the worldExtent, we will throw an ArgumentNullException.

ArgumentNullException

If you pass a null as the geoImageOrNativeImage, we will throw an ArgumentNullException.

ArgumentNullException

If you pass a null as the labeledInLayers, we will throw an ArgumentNullException.

ArgumentOutOfRangeException

If you pass in a mapUnit that is not defined in the enumeration, it will throw a ArgumentOutOfRangeException.

DrawAsyncCore(GeoCanvas, Collection<SimpleCandidate>)

protected abstract Task DrawAsyncCore(GeoCanvas canvas, Collection<SimpleCandidate> labelsInAllLayers)

Parameters

canvas GeoCanvas

labelsInAllLayers Collection<SimpleCandidate>

Returns

Task

DrawCore(GeoCanvas, Collection<SimpleCandidate>)

[Obsolete("Please use its async version instead for better efficiency and responsiveness. This sync version will no longer be available after 13.3.")]
protected override void DrawCore(GeoCanvas canvas, Collection<SimpleCandidate> labelsInAllLayers)

Parameters

canvas GeoCanvas

labelsInAllLayers Collection<SimpleCandidate>

OpenAsync(CancellationToken)

This method opens the Layer so that it is initialized and ready to use.

public Task OpenAsync(CancellationToken cancellationToken = default)

Parameters

cancellationToken CancellationToken

Returns

Task

None

Remarks

This method is the concrete wrapper for the abstract method OpenCore. The open method plays an important role, as it is responsible for initializing the Layer. Most methods on the Layer will throw an exception if the state of the Layer is not opened. When the map draws each layer, the layer will be opened as one of its first steps; then, after it is finished drawing with that layer, it will close it. In this way, we are sure to release all resources used by the Layer.

When implementing the abstract method, consider opening the FeatureSource or RasterSource. You will get a chance to close these in the Close method of the Layer.

As this is a concrete public method that wraps a Core method, we reserve the right to add events and other logic to pre- or post-process data returned by the Core version of the method. In this way, we leave our framework open on our end, but also allow you the developer to extend our logic to suit your needs. If you have questions about this, please contact our support team as we would be happy to work with you on extending our framework.

OpenAsyncCore(CancellationToken)

This method opens the Layer so that it is initialized and ready to use.

protected virtual Task OpenAsyncCore(CancellationToken cancellationToken)

Parameters

cancellationToken CancellationToken

Returns

Task

None

Remarks

This abstract method is called from the concrete public method Open. The open method plays an important role, as it is responsible for initializing the Layer. Most methods on the Layer will throw an exception if the state of the Layer is not opened. When the map draws each layer, the layer will be opened as one of its first steps; then, after it is finished drawing with that layer, it will close it. In this way, we are sure to release all resources used by the Layer.

When implementing the abstract method, consider opening the FeatureSource or RasterSource. You will get a chance to close these in the Close method of the Layer.

Exceptions

InvalidOperationException

In the event you attempt to call this method on a Layer which has already been opened, it will throw an InvalidOperationException.

OpenCore()

[Obsolete("Please use its async version instead for better efficiency and responsiveness. This sync version will no longer be available after 13.3.")]
protected override void OpenCore()