Intermittent errors trying to get text width

GemBox.Pdf
1

Using GemBox PDF version 17.0.1342.
Error occurs intermittently on Windows Server 2016 Datacenter.

The code causing the error (in simplified form), looks like this:

using GemBox.Pdf.Content;

        public double GetTextWidth()
        {
            string fontFamilyName = "Verdana";
            double fontSize = 6;
            PdfFontFamily fontFamilyToUse = new PdfFontFamily(fontFamilyName);

            string text = "999 of 999";

            double width;

            // work out width
            using (var formattedText = new PdfFormattedText())
            {
                formattedText.FontFamily = fontFamilyToUse;                
                formattedText.FontSize = fontSize;

                formattedText.Append(text);

                width = formattedText.Width;                
            }

            return width;
        }

When GetTextWidth is called, it sometimes throws a Win32Exception:

Exception: System.ComponentModel.Win32Exception
Exception Message: An attempt was made to reference a token that does not exist

Stack trace:
   at MS.Win32.UnsafeNativeMethods.RegisterClassEx(WNDCLASSEX_D wc_d)
   at MS.Win32.HwndWrapper..ctor(Int32 classStyle, Int32 style, Int32 exStyle, Int32 x, Int32 y, Int32 width, Int32 height, String name, IntPtr parent, HwndWrapperHook[] hooks)
   at System.Windows.Threading.Dispatcher..ctor()
   at System.Windows.Threading.Dispatcher.get_CurrentDispatcher()
   at   ..ctor(Boolean ,    , Double )
   at   .(   , Boolean , Double )
   at GemBox.Pdf.Content.PdfFormattedText.()
   at GemBox.Pdf.Content.PdfFormattedText.()

The Win32Exception NativeErrorCode is 1008, which in hex is: 0x000003F0 , ERROR_NO_TOKEN
in: [MS-ERREF]: Win32 Error Codes | Microsoft Learn

The code is running in a Windows Service, and GetTextWidth() will get called many times.
Any ideas ?

2

Hi,

It seems there is an issue with the WPF Dispatcher.
Just in case, please try again with this bugfix:

Install-Package GemBox.Pdf -Version 17.0.1396-hotfix

If the problem remains, can you try using the PdfTextFormattingMode.HarfBuzz like the following to avoid the usage of WPF:

using (var formattedText = new PdfFormattedText())
{
    formattedText.TextFormattingMode = PdfTextFormattingMode.HarfBuzz;
    formattedText.FontFamily = fontFamilyToUse;
    formattedText.FontSize = fontSize;

    formattedText.Append(text);
    width = formattedText.Width;
}

I hope this helps.

Regards,
Mario

3

Thanks Mario. The windows service application is running in .NET Framework 4.7.2, and does not (explicitly) use WPF. For my understanding: will that code for GetTextWidth() I’ve shown, use WPF under the hood, for this type of app ?

4

Yes exactly, please check the PdfTextFormattingMode enum.

Last, note that for the PdfTextFormattingMode.HarfBuzz you’ll need to have a HarfBuzzSharp package installed: