DrawingVisual performance with Opacity=0

Question

If I have a DrawingVisual in WPF with Opacity=0, is that enough for it not to be drawn? We have hundreds of DrawingVisuals on a Canvas, and are currently setting Opacity=0 o

Answer 1

I solved a very similar problem by using a DrawingGroup and adding or removing Drawing objects from the DrawingGroup as they either needed to be displayed or hidden. The key is to organize your Drawing objects in such a way that they are easy to manage and to understand how to add and remove them from the DrawingGroup.

Remember that you want to add and remove the Drawing objects from the DrawingCollection exposed by the DrawingGroup.Children property. So use DrawingGroup.Children.Add() or the other DrawingCollection methods: Insert, Remove, RemoveAt, Clear. You will need to keep an external list of the Drawing objects you add/remove to the DrawingGroup to do this successfully.

I used this technique to great effect by drawing an Image (bitmap) into the first child in my instance of DrawingGroup and then adding and removing Drawing objects to this instance of DrawingGroup in order to layer polygons, paths, text, etc on top of the drawing.

I "draw" or "erase" on the image by adding or removing Drawing objects to the instance of the DrawingGroup. The DrawingGroup is treated as a single Drawing and so any scaling, panning, or other manipulations will affect all Drawing objects within the DrawingGroup.