Check is needed for GDI+ implementation of AppendPath method of PdfSharp.Drawing.Pdf.XGraphicsPdfRenderer class

[MikeGratsas]

Method internal void AppendPath(GraphicsPath path) was implemented in PdfSharp v. 1.32 as follows:

            int count = path.PointCount;
            if (count == 0)
                return;
            ...

However, this additional path.PointCount check is omitted in the current version:

AppendPath(XGraphics.MakeXPointArray(path.PathPoints, 0, path.PathPoints.Length), path.PathTypes);

Therefore, if GraphicsPath is empty and doesn't contain any objects (due to invalid parameters or another reason) an exception is thrown by GDI+ reading properties path.PathPoints and path.PathTypes. In my opinion, the mentioned path.PointCount; check is still needed to prevent exceptions.

[ThomasHoevel]

In my opinion, the check is still there. Closed until we have code that reproduces a real issue.

[MikeGratsas]

I attached the solution representing the issue upgrading to PdfSharp library version 1.50. If the project references PdfSharp v. 1.32, the program execution completes successfully. However, if you change the reference to PdfSharp library version to 1.50, as implemented in the project PdfSharpApplication-1.50.5147.csproj, you will get an unhandled exception. I wonder why four years are required to fix the mentioned issue. PdfSharpApplication.zip

[ThomasHoevel]

I tried your code. No exception with 1.32, no exception with 1.50.5147.
Wasted enough time, back to working on PDFsharp 6.0.0.

[Floyddotnet]

I tried your code. No exception with 1.32, no exception with 1.50.5147. Wasted enough time, back to working on PDFsharp 6.0.0.

Hi thomas, I have not been involved in this ticket before but it caught my attention.

I tried the example project "1.50.5147" and I get an ArgumentExecption.

Stacktrace:

   at System.Drawing.Drawing2D.GraphicsPath.get_PathPoints()
   at PdfSharp.Drawing.Pdf.XGraphicsPdfRenderer.AppendPath(GraphicsPath path)
   at PdfSharp.Drawing.Pdf.XGraphicsPdfRenderer.DrawPath(XPen pen, XBrush brush, XGraphicsPath path)
   at PdfSharp.Drawing.XGraphics.DrawPath(XBrush brush, XGraphicsPath path)
   at PdfSharpApplication.Program.Main(String[] args) in C:\Users\xxx\Downloads\PdfSharpApplication\PdfSharpApplication\Program.cs:line 16

Env:

Windows 10 Pro
Visual Studio 2022 64 Bit (17.4.4)

Also, I could not see any obvious error in the project (apart from the fact that the path does not contain any points 😁)

[ThomasHoevel]

Windows 10 here. Tried VS 2017 before. Now I tried VS 17.5.4. Still no exception. I hadn't seen the "hidden" project that is not included in the solution, but still no exception with that.

And this is the code I see after pressing F12 a few times:

    /// <summary>Appends the content of a GraphicsPath object.</summary>
    internal void AppendPath(CoreGraphicsPath path) => this.AppendPath(path.PathPoints, path.PathTypes);

    private void AppendPath(XPoint[] points, byte[] types)
    {
      int length = points.Length;
      if (length == 0)
        return;
      for (int index1 = 0; index1 < length; ++index1)

[Floyddotnet]

correct, accessing path.PathPoints throws the error. internal void AppendPath(CoreGraphicsPath path) => this.AppendPath(/* ---->*/ path.PathPoints /* <----*/, path.PathTypes);

System.ArgumentException: "Ungültiger Parameter." = System.ArgumentException: "Invalid Parameter."

see Stacktrace:

at System.Drawing.Drawing2D.GraphicsPath.get_PathPoints() = get method of PathPoints property.

[Floyddotnet]

If you want i can debug this at the next days (maybe at Thusday) and give you a full investigation report.

[Floyddotnet]

btw: Maybe you disable "Break on Exception" for "ArgumentExceptions"?

[ThomasHoevel]

btw: Maybe you disable "Break on Exception" for "ArgumentExceptions"?

No, all exceptions are active. And unhandled exceptions will always throw anyway.

Please let me know if you can replicate this.

[MikeGratsas]

You should use .NET Framework, not .NET Core to find an exception.

[ThomasHoevel]

OK, I can replicate the exception now.

[TH-Soft]

The issue will be fixed with PDFsharp 6.0.0-Preview-2 (coming soon now). Those who want to stick to version 1.50 or 1.51 can make the changes themselves.

The old code (line 1333):

#if GDI
        /// <summary>
        /// Appends the content of a GraphicsPath object.
        /// </summary>
        internal void AppendPath(GraphicsPath path)
        {
#if true
            AppendPath(XGraphics.MakeXPointArray(path.PathPoints, 0, path.PathPoints.Length), path.PathTypes);
#else

The new code:

#if GDI
        /// <summary>
        /// Appends the content of a GraphicsPath object.
        /// </summary>
        internal void AppendPath(GraphicsPath path)
        {
#if true
            int count = path.PointCount;
            if (count == 0)
                return; // Nothing to do if list is empty.
            var points = path.PathPoints;
            AppendPath(XGraphics.MakeXPointArray(points, 0, points.Length), path.PathTypes);
#else

If you don't want to change the PDFsharp package, make sure you do not call AppendPath for empty paths. I don't know if NuGet packages with that fix will be published for PDFsharp 1.50 or 1.51. If possible, switch to PDFsharp 6.0.0.