ThinkGeoVectorTileAsyncLayer¶
Namespace: ThinkGeo.Core
ThinkGeo's vector basemap: the newer ThinkGeo vector tiles, drawn from a MapLibre style document. The successor to ThinkGeoVectorMapsAsyncLayer. The tiles carry more than the ones that layer reads - buildings, landcover and relief outside cities, mountain peaks, transit - and the published styles draw it.
public class ThinkGeoVectorTileAsyncLayer : WebBasedAsyncLayer, IHttpRequestService
Inheritance object → LayerBase → AsyncLayer → WebBasedAsyncLayer → ThinkGeoVectorTileAsyncLayer
Implements IHttpRequestService
Remarks:
The layer holds a ThinkGeoVectorTileSource for the tiles and a MapStyle for the cartography, and draws through CpuTileRenderer. Both are made on the first draw and kept: the open source and the compiled style are the expensive part. A property set afterwards is picked up on the next draw, and the tiles are not fetched again - the data is one dataset however it is dressed, so switching between light and dark re-reads nothing.
Asynchronous because a draw waits on the renderer, and the thread a web map draws its tiles on must not be held while it does. The tile requests go through the layer's own WebBasedAsyncLayer.HttpClient, so WebBasedAsyncLayer.WebProxy, WebBasedAsyncLayer.TimeoutInSeconds, WebBasedAsyncLayer.Credentials and the WebBasedAsyncLayer.SendingHttpRequest and WebBasedAsyncLayer.ReceivedHttpResponse events apply to them. The style document, its sprite and its glyphs are fetched once through the process's default client; a proxy for those is HttpClient.DefaultProxy.
A canvas is drawn at the density it says it has: on a display that packs more than one device pixel into a logical one, lines, icons and text come out the size they were designed at and sharper, not smaller. Cut into tiles, neighbouring tiles agree about a label that crosses the edge between them, because each is placed with a ring of its neighbours in play.
Properties¶
ApiKey¶
The apiKey every tile request carries. Required before the first draw; given to the constructor, or set here by markup. Setting it afterwards reads the tiles again under the new key.
public string ApiKey { get; set; }
Property Value¶
StyleUri¶
The style document the map is drawn from - its address or its text. ThinkGeoVectorStyles names the published ones, so light and dark are ThinkGeoVectorStyles.Light and ThinkGeoVectorStyles.Dark; any other MapLibre document is given the same way. Light by default, and setting it is picked up on the next draw without the tiles being fetched again.
public string StyleUri { get; set; }
Property Value¶
TransparentBackground¶
Draws the ink and nothing else: every area fill left out and the background left clear, so whatever is underneath shows through. What to put a street map on top of aerial imagery with. False by default - the layer is a map in its own right. Setting it is picked up on the next draw.
public bool TransparentBackground { get; set; }
Property Value¶
LabelDisplayMode¶
What a draw puts down: the shapes and the labels (the default), the shapes alone, or the labels alone. The two halves are for two overlays over one map - the shapes cut into tiles, which can be kept and are drawn from one vector tile each, and the labels drawn once over the whole view on top, where no tile edge runs through them and nothing of the application's own is drawn over them. The labels alone are drawn on a clear surface whatever ThinkGeoVectorTileAsyncLayer.TransparentBackground says. Setting it is picked up on the next draw.
public LabelDisplayMode LabelDisplayMode { get; set; }
Property Value¶
VectorTileCache¶
Where the vector tiles are kept on disk once they have been downloaded, so that a tile is asked of the server once rather than every time something is drawn from it. Null, the default, keeps nothing: every draw fetches its tiles again. These are the tiles themselves, not pictures of them - one cache serves every style.
public FileTileCache VectorTileCache { get; set; }
Property Value¶
ShowDebugInfo¶
Outlines every vector tile the view was drawn from and writes its zoom, column and row over it. For finding out which tiles a view asks for; false by default.
public bool ShowDebugInfo { get; set; }
Property Value¶
ProjectionConverter¶
Draws the map in a projection other than the tiles' own. The tiles are Web Mercator; given a converter whose internal projection is that (EPSG:3857) and whose external projection is the map's, each view is taken back to Web Mercator, drawn there with pixels square at the view's resolution, and the picture warped into the map's projection - labels included, which come out as the warp bends them. Null, the default, draws a Web Mercator map. Setting it is picked up on the next draw.
public ProjectionConverter ProjectionConverter { get; set; }
Property Value¶
Remarks:
It must be a GdalProjectionConverter (ThinkGeo.Gdal): what is warped is a picture, and the managed ProjectionConverter converts shapes but not images - warping a raster is GDAL's job in this SDK, here as in every raster layer and tile source. The layer this one succeeds converted its features one by one and so took the managed converter; this one draws a view at a time. Given a converter that cannot warp an image, the layer logs a warning when it is set and every draw fails; a map that keeps the managed converter keeps ThinkGeoVectorMapsAsyncLayer, or draws the tiles with MvtTilesAsyncLayer.
HttpClient¶
Gets or sets the HTTP client reused for outbound requests.
public HttpClient HttpClient { get; set; }
Property Value¶
Remarks:
Use this property when the caller needs full control over the entire WebBasedAsyncLayer.HttpClient instance, including its handler pipeline and default headers. When assigned before OpenAsyncCore, this property takes precedence over WebBasedAsyncLayer.HttpMessageHandler; the handler property is ignored.
Ownership remains with the caller. The layer reuses the supplied client rather than creating its own. The current implementation also applies WebBasedAsyncLayer.TimeoutInSeconds to HttpClient.Timeout during open, even when the client is caller-supplied. This can affect shared WebBasedAsyncLayer.HttpClient instances.
HttpMessageHandler¶
Gets or sets an optional HttpMessageHandler used to construct the internal WebBasedAsyncLayer.HttpClient at open time. Useful for Blazor WASM (injecting a browser-compatible handler), DelegatingHandler chains (Polly retry, OpenTelemetry, custom auth), or unit tests with mock handlers.
public HttpMessageHandler HttpMessageHandler { get; set; }
Property Value¶
Remarks:
Prefer this property over WebBasedAsyncLayer.HttpClient when the caller wants to control the transport pipeline but still allow the layer to create and own its runtime WebBasedAsyncLayer.HttpClient instance.
If both WebBasedAsyncLayer.HttpClient and WebBasedAsyncLayer.HttpMessageHandler are assigned before opening, WebBasedAsyncLayer.HttpClient wins and this property is ignored.
Behavior: Read once during OpenAsyncCore. Setting it after the layer is opened has no effect.Ignored when has already been assigned.When supplied, , , and automatic decompression are NOT applied — the caller owns the full handler chain.The handler is not disposed by this layer. Caller retains ownership (intended for singletons from IHttpClientFactory or DI).Not serialized; deserialized layers will fall back to the default handler.
WebProxy¶
Gets or sets the proxy through which all HTTP requests should be routed.
public IWebProxy WebProxy { get; set; }
Property Value¶
TimeoutInSeconds¶
Gets or sets the request timeout, in seconds.
public int TimeoutInSeconds { get; set; }
Property Value¶
Credentials¶
Gets or sets the credential provider used when authenticating HTTP requests.
public ICredentials Credentials { get; set; }
Property Value¶
UserAgent¶
This property allows you to specify a custom user-agent request header when making requests to a Web server. This header provides information about the client application or device and can be useful for server-side logging and analytics.
public string UserAgent { get; set; }
Property Value¶
UpperScale¶
This property gets and sets the upper threshold in the scale at which to display the image.
public double UpperScale { get; set; }
Property Value¶
double
This property gets the upper threshold in the scale at which to display the image.
Remarks:
Above the upper threshold in scale, the image will not be displayed. This, in conjunction with the LowerThreshold property, allows you to create a band in which it is suitable to display the image source. By default, the upper threshold is double.max and lower threshold is 0. This means the image should always display.
LowerScale¶
This property gets and sets the lower threshold in the scale at which to display the image.
public double LowerScale { get; set; }
Property Value¶
double
This property gets the lower threshold in the scale at which to display the image.
Remarks:
Below the lower threshold in scale, the image will not be displayed. This, in conjunction with the UpperThreshold property, allows you to create a band in which it is suitable to display the image source. By default, the upper threshold is double.max and lower threshold is 0. This means the image should always display.
Name¶
Gets or sets the display name for the layer.
public string Name { get; set; }
Property Value¶
string
The name used to identify the layer within UI components such as legends.
Remarks:
The name is user defined. Assign a descriptive value so tooling such as legends and layer lists can surface a meaningful label to end users.
IsOpen¶
Gets a value indicating whether the layer is currently open.
public bool IsOpen { get; }
Property Value¶
bool
true if the layer has completed its open routine; otherwise, false.
Remarks:
This method is the concrete wrapper for the abstract method IsOpenCore. Various methods on the Layer require that it be in an open state. If one of those methods is called when the state is not open, then the method will throw an exception. To enter the open state, you must call the Layer Open method. The method will raise an exception if the current Layer is already open.
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.
IsVisible¶
Gets or sets a value indicating whether the layer is visible.
public bool IsVisible { get; set; }
Property Value¶
bool
true to draw the layer; otherwise, false.
Remarks:
If this property is set to false, the layer will not draw. We ensure this in the Draw method. This is useful for legends and other controls that control the visibility of layers.
Projection¶
Gets the projection of the layer.
public Projection Projection { get; set; }
Property Value¶
DrawingExceptionMode¶
Gets or sets how drawing exceptions are handled when the layer renders.
public DrawingExceptionMode DrawingExceptionMode { get; set; }
Property Value¶
Background¶
Gets or sets the background color used when rendering the layer.
public GeoColor Background { get; set; }
Property Value¶
GeoColor
The fill applied to areas not covered by layer content.
Transparency¶
Gets or sets the amount of transparency applied to the rendered image.
public float Transparency { get; set; }
Property Value¶
float
A value between 0 (fully transparent) and 255 (fully opaque).
Opacity¶
Gets or sets the opacity applied to the rendered image.
public float Opacity { get; set; }
Property Value¶
float
A value between 0.0 (fully transparent) and 1.0 (fully opaque).
BlueTranslation¶
Gets or sets the intensity adjustment applied to the blue channel.
public float BlueTranslation { get; set; }
Property Value¶
float
A value between -255 and 255 representing the blue channel translation.
RedTranslation¶
Gets or sets the intensity adjustment applied to the red channel.
public float RedTranslation { get; set; }
Property Value¶
float
A value between -255 and 255 representing the red channel translation.
GreenTranslation¶
Gets or sets the intensity adjustment applied to the green channel.
public float GreenTranslation { get; set; }
Property Value¶
float
A value between -255 and 255 representing the green channel translation.
KeyColors¶
Gets the collection of key colors that should be rendered as transparent.
public Collection<GeoColor> KeyColors { get; }
Property Value¶
Remarks:
Attempting to access this collection when the associated GeoCanvas does not support key colors (see GeoCanvas.SupportKeyColor) results in an exception. Add colors to this collection to ensure they render as transparent.
IsNegative¶
Gets or sets a value indicating whether the image should be rendered with inverted colors.
public bool IsNegative { get; set; }
Property Value¶
bool
true to invert the color channels; otherwise, false.
IsGrayscale¶
Gets or sets a value indicating whether the image should be converted to grayscale prior to rendering.
public bool IsGrayscale { get; set; }
Property Value¶
bool
true to apply a grayscale filter; otherwise, false.
HasBoundingBox¶
Gets a value indicating whether the layer supports retrieving its bounding box.
public bool HasBoundingBox { get; }
Property Value¶
Remarks:
When this property is false, calls to or GetFullExtent throw an exception. The default implementation returns false.
ConcurrentAccess¶
Gets or sets how this layer behaves when more than one thread wants to draw it at once, and what a caller who wants concurrency should therefore do with it.
public ConcurrentAccess ConcurrentAccess { get; set; }
Property Value¶
ConcurrentAccess
unless the layer says otherwise: callers take turns on the one instance, which is what the screen renderer has done with a layer that did not say otherwise since this question was first asked.
Remarks:
A FeatureLayer that is not given a value of its own answers with its FeatureLayer.FeatureSource's, so a layer and the source it reads through cannot disagree about this.
ThreadSafe¶
Gets or sets the threading guarantees provided by the layer implementation.
public ThreadSafetyLevel ThreadSafe { get; set; }
Property Value¶
ThreadSafetyLevel
The level of thread safety that callers can expect when interacting with the layer.
Remarks:
Replaced by LayerBase.ConcurrentAccess and kept only so that code written against it is told, by name, what to use instead. It does not compile, so there is never a question of which of the two a caller meant: there is one value, and it is the other one. That matters because the translation was lossy in one direction - writing ThreadSafetyLevel.Unsafe could only pick ConcurrentAccess.UnsafeLock, and would silently undo a layer or source that had said ConcurrentAccess.UnsafeClone.
ColorMappings¶
Gets the color translation map that will be applied when rendering the layer.
public Dictionary<GeoColor, GeoColor> ColorMappings { get; }
Property Value¶
Dictionary<GeoColor, GeoColor>
WrappingMode¶
Gets or sets how the layer wraps when the map extent crosses world boundaries.
public WrappingMode WrappingMode { get; set; }
Property Value¶
WrappingExtent¶
Gets or sets the geographic extent to use when wrapping is enabled.
public RectangleShape WrappingExtent { get; set; }
Property Value¶
Constructors¶
ThinkGeoVectorTileAsyncLayer()¶
Initializes a new instance with no apiKey yet - for markup, which constructs first and sets properties after. ThinkGeoVectorTileAsyncLayer.ApiKey must be set before the first draw.
public ThinkGeoVectorTileAsyncLayer()
ThinkGeoVectorTileAsyncLayer(string)¶
Initializes a new instance over the published WorldStreets tiles, drawn in the light style.
public ThinkGeoVectorTileAsyncLayer(string apiKey)
Parameters¶
apiKey string
Your ThinkGeo apiKey; every tile request carries it.
ThinkGeoVectorTileAsyncLayer(string, string)¶
Initializes a new instance over the published WorldStreets tiles, drawn from the style document given.
public ThinkGeoVectorTileAsyncLayer(string apiKey, string styleUri)
Parameters¶
apiKey string
Your ThinkGeo apiKey; every tile request carries it.
styleUri string
The style document: see .
Methods¶
DrawAsyncCore(GeoCanvas, Collection<SimpleCandidate>)¶
Draws the basemap at the scale and centre the canvas is at, into the canvas.
protected Task DrawAsyncCore(GeoCanvas canvas, Collection<SimpleCandidate> labelsInAllLayers)
Parameters¶
canvas GeoCanvas
labelsInAllLayers Collection<SimpleCandidate>
Returns¶
CloseAsyncCore(CancellationToken)¶
protected Task CloseAsyncCore(CancellationToken cancellationToken)
Parameters¶
cancellationToken CancellationToken
Returns¶
Events¶
SendingHttpRequest¶
Occurs before an HTTP request is dispatched so callers can inspect or cancel it.
public event EventHandler<SendingHttpRequestMessageEventArgs> SendingHttpRequest;
ReceivedHttpResponse¶
Occurs after an HTTP response is received.
public event EventHandler<ReceivedHttpResponseMessageEventArgs> ReceivedHttpResponse;
DrawingException¶
Occurs when the DrawingException event is raised.
public event EventHandler<DrawingExceptionLayerEventArgs> DrawingException;
DrawnException¶
Occurs when the DrawnException event is raised.
public event EventHandler<DrawnExceptionLayerEventArgs> DrawnException;