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Vote

TrueTypeFont not working properly in multithreaded scenarios

When working in a multithreaded environment PdfTrueTypeFonts cannot be reused. The following exceptions may occur:

Starting with:

Destination array was not long enough. Check the destination index, length, and the array's lower bounds. (Parameter 'destinationArray')
   at System.Array.Copy(Array sourceArray, Int32 sourceIndex, Array destinationArray, Int32 destinationIndex, Int32 length, Boolean reliable)
   at System.Array.Copy(Array sourceArray, Array destinationArray, Int32 length)
   at System.Collections.Generic.Dictionary`2.Resize(Int32 newSize, Boolean forceNewHashCodes)
   at System.Collections.Generic.Dictionary`2.TryInsert(TKey key, TValue value, InsertionBehavior behavior)
   at Syncfusion.Pdf.Graphics.Fonts.UnicodeTrueTypeFont.SetSymbols(String text)
   at Syncfusion.Pdf.Graphics.PdfTrueTypeFont.SetSymbols(String text)
   at Syncfusion.Pdf.Graphics.PdfGraphics.ConvertToUnicode(String text, PdfTrueTypeFont ttfFont, PdfStringFormat format)
   at Syncfusion.Pdf.Graphics.PdfGraphics.DrawUnicodeLine(LineInfo lineInfo, RectangleF layoutRectangle, PdfFont font, PdfStringFormat format)
   at Syncfusion.Pdf.Graphics.PdfGraphics.DrawLayoutResult(PdfStringLayoutResult result, PdfFont font, PdfStringFormat format, RectangleF layoutRectangle)
   at Syncfusion.Pdf.Graphics.PdfGraphics.DrawStringLayoutResult(PdfStringLayoutResult result, PdfFont font, PdfPen pen, PdfBrush brush, RectangleF layoutRectangle, PdfStringFormat format)
   at Syncfusion.Pdf.Graphics.PdfGraphics.DrawString(String s, PdfFont font, PdfPen pen, PdfBrush brush, RectangleF layoutRectangle, PdfStringFormat format)
   at Syncfusion.Pdf.Graphics.PdfGraphics.DrawString(String s, PdfFont font, PdfPen pen, PdfBrush brush, Single x, Single y, PdfStringFormat format)
   at Syncfusion.Pdf.Graphics.PdfGraphics.DrawString(String s, PdfFont font, PdfPen pen, PdfBrush brush, PointF point, PdfStringFormat format)
   at Syncfusion.Pdf.Graphics.PdfTextElement.DrawInternal(PdfGraphics graphics)
   at Syncfusion.Pdf.Graphics.PdfGraphicsElement.Draw(PdfGraphics graphics, Single x, Single y)
   at Syncfusion.Pdf.Graphics.PdfGraphicsElement.Draw(PdfGraphics graphics, PointF location)
   at Syncfusion.Pdf.Graphics.PdfGraphicsElement.Draw(PdfGraphics graphics)

continuing with:
System.InvalidOperationException: Collection was modified; enumeration operation may not execute.   at System.Collections.Generic.Dictionary`2.Enumerator.MoveNext()
   at Syncfusion.Pdf.Primitives.PdfDictionary.SaveItems(IPdfWriter writer)
   at Syncfusion.Pdf.Primitives.PdfDictionary.Save(IPdfWriter writer, Boolean bRaiseEvent)
   at Syncfusion.Pdf.Primitives.PdfStream.Save(IPdfWriter writer)
   at Syncfusion.Pdf.IO.PdfCrossTable.DoSaveObject(IPdfPrimitive obj, PdfReference reference, PdfWriter writer)
   at Syncfusion.Pdf.IO.PdfCrossTable.SaveIndirectObject(IPdfPrimitive obj, PdfWriter writer)
   at Syncfusion.Pdf.IO.PdfCrossTable.SaveObjects(PdfWriter writer)
   at Syncfusion.Pdf.IO.PdfCrossTable.Save(PdfWriter writer)
   at Syncfusion.Pdf.PdfDocument.Save(Stream stream)

or

System.Collections.Generic.KeyNotFoundException: The given key '/Filter' was not present in the dictionary.
   at System.Collections.Generic.Dictionary`2.get_Item(TKey key)
   at Syncfusion.Pdf.Primitives.PdfStream.AddFilter(String filterName)
   at Syncfusion.Pdf.Primitives.PdfStream.CompressContent(IPdfWriter writer)
   at Syncfusion.Pdf.Primitives.PdfStream.Save(IPdfWriter writer)
   at Syncfusion.Pdf.IO.PdfCrossTable.DoSaveObject(IPdfPrimitive obj, PdfReference reference, PdfWriter writer)
   at Syncfusion.Pdf.IO.PdfCrossTable.SaveIndirectObject(IPdfPrimitive obj, PdfWriter writer)
   at Syncfusion.Pdf.IO.PdfCrossTable.SaveObjects(PdfWriter writer)
   at Syncfusion.Pdf.IO.PdfCrossTable.Save(PdfWriter writer)
   at Syncfusion.Pdf.PdfDocument.Save(Stream stream)


and ends up being in a deadlock situation with this error:



System.InvalidOperationException: Operations that change non-concurrent collections must have exclusive access. A concurrent update was performed on this collection and corrupted its state. The collection's state is no longer correct.
   at System.Collections.Generic.Dictionary`2.Remove(TKey key)
   at Syncfusion.Pdf.Primitives.PdfDictionary.Remove(PdfName key)
   at Syncfusion.Pdf.Primitives.PdfStream.Clear()
   at Syncfusion.Pdf.Graphics.Fonts.UnicodeTrueTypeFont.GenerateCmap()
   at Syncfusion.Pdf.Primitives.PdfDictionary.OnBeginSave(SavePdfPrimitiveEventArgs args)
   at Syncfusion.Pdf.Primitives.PdfStream.Save(IPdfWriter writer)
   at Syncfusion.Pdf.IO.PdfCrossTable.DoSaveObject(IPdfPrimitive obj, PdfReference reference, PdfWriter writer)
   at Syncfusion.Pdf.IO.PdfCrossTable.SaveIndirectObject(IPdfPrimitive obj, PdfWriter writer)
   at Syncfusion.Pdf.IO.PdfCrossTable.SaveObjects(PdfWriter writer)
   at Syncfusion.Pdf.IO.PdfCrossTable.Save(PdfWriter writer)
   at Syncfusion.Pdf.PdfDocument.Save(Stream stream)
A reproducible example is added in the attachements. It would be best to be able to reuse one cached instance for performance aspects.

Following workarounds seem to be available but all come at a cost.
  1. Use of PdfStandardFont -> No viable option most of the time
  2. Create a new PdfTrueTypeFont for each string -> Execution time and memory consumption can grow very fast
  3. Using a locking-mechanism (e.g. Semaphore) around the Save-Method seems to work -> Out method of choice for the time being as we are producing relatively small documents that are rendered fast and the throughput normally isn't too high to get in trouble. Also a good choice for us considering the overall execution time vs option 2