How to draw graphics as efficiently as possible in

问题:

I am creating a tool which relies heavily on graph-node trees. The current implementation is done in Java and I'm porting it to a generic code-base on C#, so it can be used by various rendering implementations and also because I want to use the power of WPF for a user-friendly interface.

After browsing around for a day, I came across various methods to draw Vector-graphics through WPF.

This guy speaks about different layers within WPF developers can choose from. As I want to use WPF PURELY for his rendering at first, I want to work on the "Visual Layer".

I then came across things like: DrawingVisual, GeometryDrawing, FrameworkElement / UIElement / Shapes

So, I'm a bit overwhelmed by all the different implementations that do eventually the same in totally different ways.

The Graph-Node library has been ported to C# already with all it's logic (including collision detection and dragging with mouse). As it is made with graphic-renderers in mind (like XNA, SlimDX, OpenTK, etc.), what would be the best way in terms of performance to implement a WPF renderer (as in, it will draw whatever the graph library tells it to draw?

Basically, the resulting WPF control acts as a canvas, but it has to be SUPER lightweight and not have any neat WPF features besides providing me a way to draw my circles, lines and other shapes :)

EDIT:

I basically want to know: What is the way to go? Do I extend Canvas as "Host" for my graphics and then add my custom implementation of a UIElement? Or can I have one class which can draw EVERYTHING (as in, one mega super ultra graphic). Much like overriding OnPaint in GDI or Paint-method in Java (which gives a Graphics object to do everything with).

回答1:

I'd recommend reading Optimizing Performance: 2D Graphics and Imaging (dead link -- readable via Internet Archive) -

Basically, Drawing objects will be lighter weight than Shapes, in general. This is probably what you want to use.

回答2:

Generally, better performance is obtained with lower-level services. In WPF, this means the Drawing family of objects. All you get are: Drawing, DrawingGroup, GeometryDrawing, GlyphRunDrawing, ImageDrawing, and VideoDrawing. However, they are sufficient for all needs. Using these types is very friendly with WPF because Drawing is the conceptual unit that WPF exchanges with your GPU accelerator, possibly retaining and managing it there if possible. This works because the Drawing is expressed in terms of portable vector drawing primitives.

Once you start re-architecting your app around Drawings however, you might need some interop with your higher-level code which is still based on UIElement, FrameworkElement, etc. One thing that I haven't found built-in to WPF is a simple way to wrap a Drawing as a FrameworkElement in the lowest-overhead way possible. DrawingVisual isn't a complete solution, because it only derives from Visual--meaning it still requires a hosting element.

The following class will host any WPF Drawing directly without using an intermediate DrawingVisual. I added support for FrameworkElement's Margin property (with no performance penalty if unused) but little else. Because of WPF's single rendering thread it's safe and easy to cache a single TranslateTransform object to implement the margin. I'd recommend that you supply only drawings which have been Frozen; in fact, in the version that I use, I have an assert to that effect in the constructor.

public class DrawingElement : FrameworkElement
{
    static readonly TranslateTransform tt_cache = new TranslateTransform();

    public DrawingElement(Drawing drawing)
    {
        this.drawing = drawing;
    }
    readonly Drawing drawing;

    TranslateTransform get_transform()
    {
        if (Margin.Left == 0 && Margin.Top == 0)
            return null;
        tt_cache.X = Margin.Left;
        tt_cache.Y = Margin.Top;
        return tt_cache;
    }
    protected override Size MeasureOverride(Size _)
    {
        var sz = drawing.Bounds.Size;
        return new Size
        {
            Width = sz.Width + Margin.Left + Margin.Right,
            Height = sz.Height + Margin.Top + Margin.Bottom,
        };
    }
    protected override void OnRender(DrawingContext dc)
    {
        var tt = get_transform();
        if (tt != null)
            dc.PushTransform(tt);
        dc.DrawDrawing(drawing);
        if (tt != null)
            dc.Pop();
    }
};

[edit:] This is also useful for inserting a WPF Drawing into the InlineUIContainer.Child property (i.e. using TextBlock.InlinesCollection to format the contents of the TextBlock more richly).

回答3:

the DrawingVisual seems to be a valid choice:

The DrawingVisual is a lightweight drawing class that is used to render shapes, images, or text. This class is considered lightweight because it does not provide layout or event handling, which improves its performance. For this reason, drawings are ideal for backgrounds and clip art.

source: Using DrawingVisual Objects

so this seems to be absolutely what you ask, a Canvas SUPER lightweight.