Update samples and add to main solution

[JimBobSquarePants]

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Description

Updates the samples project to use the latest API and includes it in the solution so we don't forget about it in the future.

[codecov]

Codecov Report

Merging #157 (7bf8be5) into master (653cf5f) will increase coverage by 0.05%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #157      +/-   ##
==========================================
+ Coverage   69.87%   69.92%   +0.05%     
==========================================
  Files          88       88              
  Lines        5135     5144       +9     
  Branches     1048     1052       +4     
==========================================
+ Hits         3588     3597       +9     
  Misses       1337     1337              
  Partials      210      210              

Flag	Coverage Δ
unittests	69.92% <100.00%> (+0.05%)	⬆️

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Impacted Files	Coverage Δ
src/ImageSharp.Drawing/Shapes/PathExtensions.cs	61.90% <100.00%> (+28.57%)	⬆️

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[tocsoft]

generally fine but looks like you have issue with the draw along path sample... looks like you have incorrectly changed the semantics.

[tocsoft]

this isn't the same thing.... (if i'm reading this right this is drawing along a path)

Imagine this path was a circle, the length of the circle in this case would be its circumference, whereas the width would just be its diameter meaning the text would only get partly around the outside before wrapping and not once it closes in itself.

[JimBobSquarePants]

Length isn’t a property anymore so how would I calculate it?

[antonfirsov]

An approximation is a sum of distances between subsequent path.Flatten().Single().Points. (I assume Flatten returns a single ISimplePath for this, but I may be wrong.)

[tocsoft]

without the limitation on single path...

static float GetLength(IPath path)
{
    float dist = 0;
    foreach (var s in path.Flatten())
    {
        var points = s.Points.Span;
        if (points.Length < 2)
        {
            // only a point
            continue;
        }

        for (var i = 1; i < points.Length; i++)
        {
            dist += Vector2.Distance(points[i - 1], points[i]);
        }

        if (s.IsClosed)
        {
            dist += Vector2.Distance(points[0], points[points.Length - 1]);
        }
    }

    return dist;
}

we should/could probably add this this as an extension on IPath, or re add it back to the IPath interface.

definitely makes the sample you threw into slack a little less broken.

[antonfirsov]

Unless we had the implementations calculating the length analytically, this should be an extension method. I would name it .CalculateApproximateLength().

[JimBobSquarePants]

As I recall there were issues calculating it as a property in ComplexPolygon. I’d rather avoid re-adding it to the interface and use an extension.

[JimBobSquarePants]

I went with ComputeLength() to match the DirectX method that does the same thing.

https://docs.microsoft.com/en-us/windows/win32/direct2d/id2d1geometry-computelength

[tocsoft]

We probably want a test that verifies the length calculates as expected for more complex paths too... i.e. any IPath where the Flatten() call returns multiple ISimplePaths

[JimBobSquarePants]

I looked for and couldn’t find one in the codebase from before IPath.Length was removed to reuse. With nothing to verify against I’m just been guessing the result.

[JimBobSquarePants]

I'm going to need a little help here.

I used LottieSharp to calculate a polygon length since it gave me access to the original DX method and attempted to replicate a polygon to match another test one.

var p = new LottieSharp.Path();
p.MoveTo(15, 0);
p.LineTo(25, 0);
p.MoveTo(15, 30);
p.LineTo(25, 0);
p.Close();

using (var factory = new SharpDX.Direct2D1.Factory(SharpDX.Direct2D1.FactoryType.SingleThreaded))
{
	p.GetGeometry(factory).ComputeLength().Dump(); // 73.24555
}

Our test code.

[Fact]
public void CanComputeUnrolledLength()
{
    var pb = new PathBuilder();
    pb.AddLine(new Vector2(15, 0), new Vector2(25, 0))
        .AddLine(new Vector2(15, 30), new Vector2(25, 30))
        .CloseFigure();

    IPath p = pb.Build();
    Assert.Equal(73.24555, p.ComputeLength()); // 83.24555206298828
}

We seem to be calculating a value exactly 10 more than the DX. I couldn't figure out a way to convert their types to ours to verify the output.

Tbh though, I don't understand how either is getting that number. The path should be a rectangle of sides 10x30 which would make the length 80 shouldn't it?

SkiaSharp seems to give me junk. Not sure what I'm doing wrong there.

using var p = new SKPath();
p.MoveTo(15, 0);
p.LineTo(25, 0);
p.MoveTo(15, 30);
p.LineTo(25, 0);
p.Close();

var measure = new SKPathMeasure(p, false, 1);
measure.Length.Dump(); // 10

[tocsoft]

I feel your overthinking this too much..... all you want is:

[Fact]
public void CanComputeUnrolledLengthComplexPath()
{
    var polygon = new ComplexPolygon(
        new RectangularPolygon(PointF.Empty, new PointF(100, 200)),
        new RectangularPolygon(new PointF(1000, 1000), new PointF(1100, 1200)));

    Assert.Equal(1200, polygon.ComputeLength());
}

this just ensures that Flatten() returns multilple ISimplePaths and that we sum the distances across all the ISimplePaths rather than just the first or any other logic.

[tocsoft]

btw your use of path builder isn't the same in your 2 samples. we don't have a move line equivalent option, the 2nd add line call adds a line joining the end of the first and the start of the 2nd and then the CloseFigure joins the start and the end, which explains the confusion in the length differences.

[JimBobSquarePants]

Oh I'm definitely overthinking things! 😄

We should probably add MoveTo and LineTo methods then shouldn't we (or have I missed an equivalent)?

I'm still intrigued by the result. I must be visualizing something badly because it seemed like a rectangle to me.