Picture Model and Rebuild

One of the more useful parts of Svg.Skia is that it does not stop at "load and draw". The runtime keeps several layers alive, and each layer has a different rebuild story.

The available layers

After loading, SKSvg can expose:

SourceDocument for authored SVG DOM work,
RetainedSceneGraph for compiled-node inspection and incremental mutation refresh,
Model for low-level ShimSkiaSharp.SKPicture command editing,
Picture for the current native SkiaSharp.SKPicture.

Choose the layer that matches the kind of change you are making.

Full document rebuild

When the DOM changes structurally or when the simplest path is good enough, mutate the document and call FromSvgDocument(...) again:

using System.Drawing;
using Svg;
using Svg.Skia;

using var svg = new SKSvg();
svg.FromSvg("<svg width=\"10\" height=\"10\"><rect id=\"r\" width=\"10\" height=\"10\" fill=\"red\" /></svg>");

var rect = (SvgRectangle)svg.SourceDocument!.GetElementById("r")!;
rect.Fill = new SvgColourServer(Color.BlueViolet);

svg.FromSvgDocument(svg.SourceDocument);

This recompiles the retained scene and regenerates the current Picture.

Retained-scene mutation refresh

For small localized DOM edits, update the scene-backed document and ask the retained scene to recompile only the affected compilation roots:

using System.Drawing;
using Svg;
using Svg.Skia;

using var svg = new SKSvg();
svg.FromSvg("<svg width=\"10\" height=\"10\"><rect id=\"r\" width=\"10\" height=\"10\" fill=\"red\" /></svg>");

var scene = svg.RetainedSceneGraph!;
var rect = (SvgRectangle)scene.SourceDocument!.GetElementById("r")!;
rect.Fill = new SvgColourServer(Color.BlueViolet);

svg.TryApplyRetainedSceneMutationByIdAndRender("r", new[] { "fill" }, out var result);

This path keeps the current Picture refreshed without paying for a full rebuild every time.

Accessing the model

SKSvg.Model exposes the ShimSkiaSharp.SKPicture command tree. This is the structure that SkiaModel later turns into SkiaSharp.SKPicture.

Editing commands

Because the model is a plain command graph, you can inspect and mutate it before rebuilding the final picture:

using System.Linq;
using ShimSkiaSharp;
using Svg.Skia;

var svg = new SKSvg();
svg.FromSvg("<svg width=\"10\" height=\"10\"><rect width=\"10\" height=\"10\" fill=\"red\" /></svg>");

foreach (var cmd in svg.Model?.Commands?.OfType<DrawPathCanvasCommand>() ?? Enumerable.Empty<DrawPathCanvasCommand>())
{
    if (cmd.Paint?.Color is { } color)
    {
        cmd.Paint.Color = new SKColor(color.Red, color.Red, color.Red, color.Alpha);
    }
}

svg.RebuildFromModel();

Avalonia rebuild flow

The same ideas exist in the Avalonia wrappers:

Avalonia.Svg.Skia.SvgSource.RebuildFromModel()
Avalonia.Svg.Skia.SvgSource.ReLoad(...)
Avalonia.Svg.Skia.SvgSource.LoadFromSvgDocument(...)
Avalonia.Svg.SvgSource.RebuildFromModel()

This makes it possible to keep an SVG-backed image source in XAML while still choosing between DOM rebuilds, parameter reloads, and low-level model mutation from code.

Cloning

The Avalonia image and source types provide cloning helpers so you can keep one original asset and derive modified variants without mutating shared state:

SvgSource.Clone()
SvgImage.Clone()

When to use each rebuild path

Use FromSvgDocument(...) when:

you added or removed elements,
the root document changed,
the simplest rebuild path is more important than maximum refresh performance.

Use retained-scene mutation refresh when:

one element or subtree changed,
you know which attributes changed,
you want to reuse the existing compiled scene as much as possible.

Use Model plus RebuildFromModel() when:

CSS alone is not expressive enough,
the asset must stay embedded but the commands need a runtime tweak,
you want to derive monochrome or recolored variants from one source,
you need testing hooks around specific command types.