Hangs when drawing a path

Prerequisites

I have written a descriptive issue title
I have verified that I am running the latest version of ImageSharp.Drawing
I have verified if the problem exist in both DEBUG and RELEASE mode
I have searched open and closed issues to ensure it has not already been reported

Description

I had a bug in my code that set some (admittedly unreasonable) paths but when running it appears to get stuck and run forever in FixupIntersectionOrder.

Steps to Reproduce

I made a small project that reproduces it https://github.com/Fenyx4/SixLaborsHang
Probably could be made even smaller but I recreated the exact instance I ran into.

System Configuration

ImageSharp.Drawing version: 1.0.0-beta15 (and 1.0.0-beta13)
Other ImageSharp packages and versions:
Fonts 1.0.0-beta18
ImageSharp 2.1.3
Environment (Operating system, version and so on):
Windows 10
.NET Framework version:
3.1
Additional information:
Visual Studio 2022 - 17.3.2

This reproduction you provided is very big, it will be really hard to debug this in this form. Can you try to make it simpler?

FYI I have been working on trimming this down.

As I trimmed it down I did discover a few things. It does not appear to run forever just a long, long time. Trimmed down versions run around an hour. When I remove some of the lines it drops down to around a minute. So I have been removing lines that don't cause it to drop below 50 minutes.

Oddly some lines I remove have caused the time to increase.

I'll keep working on getting a simpler version that still takes a long time but wanted to let you know the above in case it helps.

Allrighty! Trimmed it down as much as I could and still have it above 50 minutes.

Hope that helps.

Does the hang occur during the PathBuilder.ClosePath operation or during the actual drawing operation?

Actual drawing operation

The issue here is in the .GenerateOutline() extension/clipper library.

A much reduced case can be found with

var pathBuilder = new PathBuilder();
var transform = Matrix3x2.CreateRotation(-0.04433158f, new Vector2(948, 640));
pathBuilder.SetTransform(transform);
pathBuilder.AddQuadraticBezier(new PointF(-2147483648, 677), new PointF(-2147483648, 675), new PointF(-2147483648, 675));
IPath path = pathBuilder.Build();

// this line hangs/takes ages inside the 'clipper'
var outline = path.GenerateOutline(2);

this is the entry line that ends up hanging/taking a long time.

ImageSharp.Drawing/src/ImageSharp.Drawing/Shapes/Clipper/clipper.cs

Line 4828 in dc838dc

public void Execute(ref Paths solution, double delta)

Looks like Clipper2 is out! Maybe we could try dropping it in as a replacement?

https://github.com/AngusJohnson/Clipper2/releases/tag/Clipper2_1.0.4

Clipper2 seems to have the same problem. Will need to create an example and submit an issue/PR upstream.

We also cannot use them as a NuGet dependency as the library is not strong named.

Fix #244

Will be fixed with #377

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Hangs when drawing a path #244

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Hangs when drawing a path #244

Description

Prerequisites

Description

Steps to Reproduce

System Configuration

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brianpopow commented on Sep 1, 2022

Fenyx4 commented on Sep 6, 2022

Fenyx4 commented on Sep 13, 2022

JimBobSquarePants commented on Sep 13, 2022

Fenyx4 commented on Sep 19, 2022

tocsoft commented on Sep 19, 2022

JimBobSquarePants commented on Sep 20, 2022

JimBobSquarePants commented on Oct 24, 2022

JimBobSquarePants commented on Mar 12, 2026

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