c# iText7 how to set the position of the top left corner of a paragraph

Question

I wan't write a paragraph in the pdf file so that the top left corner of the paragraph is exactly positioned at the top left corner of the page 100,100.The code:

var targetPdfPath = "100x100.pdf";
using (PdfDocument pdfDoc = new PdfDocument(new PdfWriter(targetPdfPath)))
{
    Document document = new Document(pdfDoc);
    var page = pdfDoc.AddNewPage(PageSize.A4);
    Paragraph paragraph = new Paragraph("Must be at (100,100)");
    PdfFont FontHELVETICA = PdfFontFactory.CreateFont(StandardFonts.HELVETICA);
    paragraph.SetFontSize(20f);
    var pageHeight = PageSize.A4.GetHeight();
    PdfCanvas pdfCanvas = new PdfCanvas(page);
    var rectHeight = 200f;
    var rectWidth = 200f;
    pdfCanvas.SetLineWidth(0.5f);
    pdfCanvas.Rectangle(100, pageHeight - 100 - rectHeight, 200, 200);//It is easy to place the rectangle in the position of (100,100)pt
    pdfCanvas.Stroke();

    Canvas canvas = new Canvas(pdfCanvas, PageSize.A4);
    var paragraphHeight = 0f;//How to get it??
    paragraph.SetFixedPosition(100, pageHeight - 100f - paragraphHeight, 200);//It is difficult to place paragraphs in the position of (100,100)pt
    canvas.Add(paragraph);
}

I can't get the right result no matter how much I test.How can I do? 100x100.pdf

Answer 1

You already use a Canvas. How about setting the Canvas area to have its upper left corner at (100, 100) and let iText do the layout work:

Canvas canvas = new Canvas(pdfCanvas, PageSize.A4.ApplyMargins(100, 0, 0, 100, false));
canvas.Add(paragraph);

You may have to set the paragraph margin and padding to 0 before adding:

paragraph.SetMarginTop(0);
paragraph.SetPaddingTop(0);

(PositionParagraph test PositionParagraphAt100_100)

(I don't have Adobe Illustrator, so I cannot check whether this conforms to Illustrator's idea of the top left corner of the text.)