How do I determine column number using itext 7 - itext7

Question

I have created documents using itext 7 and its ColumnDocumentRenderer. I would like to force some text into the last column. By "last column" I mean for example if I have a single page defined by ColumnDocumentRenderer to have 3 columns but I only have one column of text, I still want column 3 to contain my forced value. So I suppose (presupposing a solution, others appreciated) that I would need mechanisms to know the column number I'm in and to force a column break. Since StackOverflow wants this in the form of a question, (a) what are these mechanisms? and (b) what are alternative approaches?
Question How to skip text insertion point to the next column using iText? apparently asks a similar question but apparently is using an earlier release of itext; mine has no ColumnText that I can find.
Thanks in advance for any help.

Answer 1

I was answering from my phone yesterday, but now that I have access to a computer, I changed ColumnDocumentRenderer like this:
public class ColumnDocumentRenderer extends DocumentRenderer {
protected Rectangle[] columns;
protected int nextAreaNumber;
public ColumnDocumentRenderer(Document document, Rectangle[] columns) {
super(document);
this.columns = columns;
}
public ColumnDocumentRenderer(Document document, boolean immediateFlush, Rectangle[] columns) {
super(document, immediateFlush);
this.columns = columns;
}
#Override
protected LayoutArea updateCurrentArea(LayoutResult overflowResult) {
if (overflowResult != null && overflowResult.getAreaBreak() != null && overflowResult.getAreaBreak().getType() != AreaBreakType.NEXT_AREA) {
nextAreaNumber = 0;
}
if (nextAreaNumber % columns.length == 0) {
super.updateCurrentArea(overflowResult);
}
return (currentArea = new LayoutArea(currentPageNumber, columns[nextAreaNumber++ % columns.length].clone()));
}
public int getNextAreaNumber() {
return nextAreaNumber;
}
}
The change will be in iText 7.0.1, but you can use this code in your own renderer.
You can now use this renderer like this:
public void createPdf(String dest) throws IOException {
OutputStream fos = new FileOutputStream(dest);
PdfWriter writer = new PdfWriter(fos);
PdfDocument pdf = new PdfDocument(writer);
Document document = new Document(pdf);
float offSet = 36;
float gutter = 23;
float columnWidth = (PageSize.A4.getWidth() - offSet * 2) / 3 - gutter * 2;
float columnHeight = PageSize.A4.getHeight() - offSet * 2;
Rectangle[] columns = {
new Rectangle(offSet, offSet, columnWidth, columnHeight),
new Rectangle(offSet + columnWidth + gutter, offSet, columnWidth, columnHeight),
new Rectangle(offSet + 2 * (columnWidth + gutter), offSet, columnWidth, columnHeight)};
ColumnDocumentRenderer renderer = new ColumnDocumentRenderer(document, columns);
document.setRenderer(renderer);
for (int i = 0; i < 50; i++) {
document.add(new Paragraph("Hello World"));
}
while (renderer.getNextAreaNumber() % 3 != 0)
document.add(new AreaBreak());
document.add(new Paragraph("Third column"));
document.add(new AreaBreak());
for (int i = 0; i < 80; i++) {
document.add(new Paragraph("Hello World"));
}
while (renderer.getNextAreaNumber() % 3 != 0)
document.add(new AreaBreak());
document.add(new Paragraph("Third column"));
document.add(new AreaBreak());
for (int i = 0; i < 10; i++) {
document.add(new Paragraph("Hello World"));
}
while (renderer.getNextAreaNumber() % 3 != 0)
document.add(new AreaBreak());
document.add(new Paragraph("Third column"));
document.close();
}
The first column has index 0 and the next area number is 1, the second column has index 1 and the next area number is 2, and so on.
This means that you can check for and go to the third column on a page like this.
while (renderer.getNextAreaNumber() % 3 != 0)
document.add(new AreaBreak());