ICustomVisualizer.Draw Method
Draws the specified feature.
Draw(Feature feature, Drawable drawable)
Draws the specified feature.Syntax
public CustomVisualizerCacheHint Draw (
Feature feature,
Drawable drawable
)Parameters
The feature to draw.
The drawable to draw on.
Return Value
A value indicating under which circumstances the result of the drawing calls just made can be cached.
Remarks
This method is called by Carmenta Engine to draw a feature with this custom visualizer, in 2D. The visualizer typically extracts the geometry from the feature, manipulates it if necessary, creates pens and brushes and then calls the drawing methods of the supplied drawable. It may also use and/or modify the 2D affine transform held by the drawable.
The feature will always be in the View.Crs (the coordinate reference system of the view). The 2D transform of the drawable will always be set up before each call so that it maps directly from the Crs coordinates to screen pixels.
The custom visualizer may use other visualizers to do some or all of the visualization. For instance, if you wish to draw a line feature with a complex line style, but you wish to modify the line in some way first, you could do it like this: First get the geometry of the line, modify it the way you want it, create a temporary line feature with the new geometry, and call the Visualizer.Draw method of an existing line visualizer.
The value returned from this method indicates under which circumstances Carmenta Engine may cache the visualization just produced by the call. If the visualization is cached, it may be reused the next time the feature should be drawn, and Carmenta Engine does not need to call out to the custom visualizer again. See CustomVisualizerCacheHint for further information. Note: This caching mechanism only works if the custom visualizer is contained in a caching layer, like a TileLayer, or a buffered OrdinaryLayer. If the layer is not cached, the return value from this method is ignored.
The PixelSizeAdjustments instance available through the drawable can be used to scale the rendering, to make it look good on both normal and high DPI monitors. If the visualizer calls other visualizers to do the rendering, the adjustments will be applied automatically.
Platforms
Windows, Linux, Android