ITextPDF - Link creation with PDFAnnotation - itext

Question

I have a question about hyperlinks within pdf documents created with itext. Currently, using the following code written in java, I am able to successfully create links. However, when I hover over the link, the link text is displayed. The client does not want the link text to appear upon hover-over. How can I either remove the hover-over, or give it alternate text to display (e.g. "Course Info")? I am using itext version 5.5.9. I have looked at "iText in Action" chapter 7 but was not able to find what I needed. Is there a better way to create the links? Any help and examples will be appreciated. Thanks.
package edu.ucsd.act.academic.studente2t.util;
import com.itextpdf.text.Rectangle;
import com.itextpdf.text.pdf.PdfAction;
import com.itextpdf.text.pdf.PdfAnnotation;
import com.itextpdf.text.pdf.PdfBorderArray;
import com.itextpdf.text.pdf.PdfContentByte;
import com.itextpdf.text.pdf.PdfPCell;
import com.itextpdf.text.pdf.PdfPCellEvent;
import com.itextpdf.text.pdf.PdfWriter;
class LinkInCellEvent implements PdfPCellEvent
{
protected String url;
public LinkInCellEvent(String url)
{
this.url = url;
}
public void cellLayout(PdfPCell cell, Rectangle position,
PdfContentByte[] canvases)
{
PdfWriter writer = canvases[0].getPdfWriter();
PdfAction action = new PdfAction(url);
PdfAnnotation link = PdfAnnotation.createLink(writer, position,
PdfAnnotation.HIGHLIGHT_INVERT, action);
PdfBorderArray border = new PdfBorderArray(0, 0, 0);
link.setBorder(border);
writer.addAnnotation(link);
}
}

Answer 1

This is not an iText problem. It's inherent to PDF. The PDF specification (ISO-32000-1) doesn't say anything about the way viewers should present tool tips for link annotations.
Your client (who probably should also be our client), may be confused by the following concepts:
Additional actions
The only occurrence of the word "tool tip" is in a NOTE when the E (enter) and X (exit) event are described in the section about additional actions. One can use additional actions, for instance on a widget annotation, to have a custom tool tip appear / disappear when someone hovers over a widget annotation.
When you study the PDF standard, you will see that there are several instances where you can define additional action (/AA), but link annotations aren't one of them.
Alternative field name
There's also the /TU entry (formerly known as the user name entry), which is (I quote the spec) an alternative field name that shall be used in place of the actual field name wherever the field shall be identified in the user interface (such as in error or status messages referring to the field). This text is also useful when extracting the document’s contents in support of accessibility to users with disabilities or for other purposes. The value of the /TU entry is often used by viewers as a tool tip, but as you can tell from the description, the /TU entry is specific for fields, not for annotations. It can only be used in a field dictionary, not in an annotation dictionary.
Conclusion:
Whatever is shown when someone hovers over a link annotation is not described in the specification. Every vendor of a PDF viewer may decide what to show (if anything) when a user hovers over a link annotation. There is no way to add something to the PDF that can force the viewer to show something else (or nothing).