Overlay¶

Namespace: ThinkGeo.UI.WebApi

Provides base functionality for WebApi overlays, including drawing lifecycle hooks and exception handling.

public abstract class Overlay

Inheritance Object → Overlay

Properties¶

Id¶

Gets the identifier that external callers can use to reference this overlay.

public string Id { get; }

Property Value¶

String
Overlay identifier supplied at construction.

IsVisible¶

Gets or sets a value indicating whether this overlay participates in draw requests.

public bool IsVisible { get; set; }

Property Value¶

Boolean
true when the overlay should render; otherwise, false.

DrawingExceptionMode¶

Gets or sets the strategy used when an exception occurs while drawing.

public DrawingExceptionMode DrawingExceptionMode { get; set; }

Property Value¶

DrawingExceptionMode
One of the values.

Methods¶

Draw(GeoCanvas)¶

Renders the overlay onto the provided while honoring Overlay.DrawingExceptionMode and raising lifecycle events.

public void Draw(GeoCanvas geoCanvas)

Parameters¶

geoCanvas GeoCanvas
Canvas that receives the overlay output.

DrawCore(GeoCanvas)¶

When overridden in a derived class, draws the overlay contents onto the supplied canvas.

protected abstract void DrawCore(GeoCanvas geoCanvas)

Parameters¶

geoCanvas GeoCanvas
Canvas to receive the overlay output.

DrawException(GeoCanvas, Exception)¶

Handles draw failures by delegating to .

protected void DrawException(GeoCanvas geoCanvas, Exception e)

Parameters¶

geoCanvas GeoCanvas
Canvas that should display the fallback visual.

e Exception
Exception that caused the draw operation to fail.

DrawExceptionCore(GeoCanvas, Exception)¶

Provides the overridable implementation that renders a diagnostic placeholder when drawing fails.

protected void DrawExceptionCore(GeoCanvas geoCanvas, Exception e)

Parameters¶

geoCanvas GeoCanvas
Canvas that should display the fallback visual.

e Exception
Exception that caused the draw operation to fail.

OnDrawing(DrawingOverlayEventArgs)¶

Raises the Overlay.Drawing event before drawing so subscribers can inspect or cancel rendering.

protected void OnDrawing(DrawingOverlayEventArgs e)

Parameters¶

e DrawingOverlayEventArgs
Event data describing the pending draw operation.

OnDrawn(DrawnOverlayEventArgs)¶

Raises the Overlay.Drawn event after drawing so subscribers can perform post-processing.

protected void OnDrawn(DrawnOverlayEventArgs e)

Parameters¶

e DrawnOverlayEventArgs
Event data that references the completed draw.

Events¶

Drawing¶

Raised before the overlay begins drawing.

public event EventHandler<DrawingOverlayEventArgs> Drawing;

Drawn¶

Raised after the overlay finishes drawing.

public event EventHandler<DrawnOverlayEventArgs> Drawn;