Fix text bugs in SynPDF

[iadcode]

These changes fix some bugs in SynPDF:

• The first commit ensures that text rendering respects the bounding rectangle correctly
• The second commit fixes a bug where strikethroughs and underlines were not drawn correctly, with respect to document scaling

Before the changes After the changes

This behaviour can be tested with code such as

  procedure EmfToPdf(EmfFilename: String; PdfFilename: String);
  const
    C_PDFPPI = 72;
    C_MMperInch = 25.4;
  var
    PDFDocument: TPdfDocument;
    Metafile: TMetafile;
    Scale: Single;
  begin
    Metafile := TMetafile.Create;
    try
      Metafile.LoadFromFile(EmfFilename);
      PDFDocument := TPdfDocument.Create(False, 0, False);
      try
        PDFDocument.DefaultPaperSize := psA4;
        PDFDocument.ScreenLogPixels := C_PDFPPI;
        PDFDocument.AddPage;
        Scale := C_PDFPPI / Trunc((Metafile.Width * 100) / (Metafile.MMWidth / C_MMperInch));
        PDFDocument.Canvas.RenderMetaFile(Metafile, Scale, Scale, 0, 0, tpSetTextJustification, 99, 101, tcAlwaysClip);
        PDFDocument.SaveToFile(PdfFilename);
      finally
        FreeAndNil(PDFDocument);
      end;
    finally
      FreeAndNil(Metafile);
    end;
  end;

And using an EMF such as the one in this zip: BugsEMF.zip