How to Generate Table-of-Figures Dot Leaders in a

问题:

I have a Table of Figures generated using PDFPTable like so.

-------------------------------------- 
|Caption|Figure Title           |  PP|
-------------------------------------- 
| fig 1 |title text             |  2 |
--------------------------------|----|
| fig 2 | This is a longer title|    |
|       | text that wraps       | 55 |
--------------------------------------
| fig N | another title         | 89 |
--------------------------------------

I need to generate leader dots from the last line of text; it may have wrapped in the cell.

Here's a sample again showing the Figure 2 item of wrapped titled text and additionally having leader dots from the end of the text to the right side of the cell.

| fig 2 | This is a longer title|    |
|       | text that wraps.......| 55 |

This is what I want to achieve.

When I write the cell text I don't know where it will wrap and therefore I don't know what the last line of text will be for the purpose of measuring it, and if I do know about the last line of text I'm hard pressed to find the immediate x position following it.

So far, I've tried harnessing Cell Events and Table Events to write the leader dots after the fact. The two problems that have stopped me so far are:

1. I can't find the x position directly after the last line of wrapped text.

2. If I try the strategy of underlying dots beneath the entire last line of text (so I don't have to know where it stops in the x position. I do now the y position) the only canvas that allows the dots to appear is PdfPTable.TEXTCANVAS however it writes the leader dots on top of the existing text instead of beneath. I can give the text chunk a background color, so if some leader dots exist behind it they will not be visible (a poor man's crop).

I'm open to any strategy inside the context of the PDFPTable.

回答1:

First things first: +1 for your question and the answer you provided yourself.

But...

Although your answer may work, there is a better way to achieve your goal. I've written a small sample called DottedLineLeader as an alternative that will be much easier to maintain. This example uses the DottedLineSeparator wrapped in a Chunk object.

Take a look at how such a chunk separator is used:

Chunk leader = new Chunk(new DottedLineSeparator());
Paragraph p;
p = new Paragraph("This is a longer title text that wraps");
p.add(leader);

When we add this Paragraph to a PdfPCell, we get the following effect:

The dots in the dotted line are not '.' characters. Instead it's an actual line (vector data) with a specific dash pattern. Using this approach instead of your own, will significantly reduce the number of lines in your code, use less CPU and result in cleaner PDFs.

回答2:

Here's one solution that suffices the question requirements.

Each PdfPCell object has a .Column property that "Returns the list of composite elements of the column". Its property ColumnText.LastX returns "The X position after the last line that has been written". This is the position where we want the leader dots to start.

This work can be done in the PdfPTablEvent.TableLayout handler where all the cell positions are known.

class TofEvents : IPdfPTableEvent {
    public void TableLayout(PdfPTable table, float[][] widths, float[] heights, int headerRows, int rowStart, PdfContentByte[] canvases)
    {
      // do the work here 
    }
 }

Because we know where the last line of the text ends on the page, and where the right side the cell is, we can fill that space with dots.

General calculation for creating the proper number of dots for a particular cell is:

// You'll have to get references to things you need from the handler method args - 
float ptXCellLeft = GetLeftSideOfCellFromIncomingWidthsArgument();
PdfPCell cell = GetCurrentCellFromIncomingCellsArgument(); 

// the math - 
Font f = getTheFontToUse(); // for measuring the text size in this font 
float leaderDotSymbolWidth = f.BaseFont.GetWidthPoint(".", f.Size);
float leaderDotsWidth = cell.Width - (cell.Column.LastX - ptXCellLeft);
string strLeaderDotsFillText = ".".Repeat(Convert.ToInt32(leaderDotsWidth / leaderDotSymbolWidth));

The resulting strLeaderDotsFillText should fit nicely into the last line's space.