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PDFsharp - A .NET library for processing PDF & MigraDoc Foundation - Creating documents on the fly
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PostPosted: Thu Apr 23, 2015 1:22 pm 
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Joined: Thu Apr 23, 2015 11:50 am
Posts: 2
Hi everyone,

I spent the whole day trying to find out why one of my MigraDoc tables is showing weird borders.
Finally, I managed to create a bugfix and want to let the developers know about it.
Because my original table is pretty large, I broke the little nasty bug down to a smaller table like this one:

Code:
Document document = new Document();   
Section section = document.AddSection();
Table table = section.AddTable();

Column col = table.AddColumn();
col.Borders.Left.Width = 2;

col = table.AddColumn();
col.Borders.Left.Color = Colors.Red;
col.Borders.Left.Width = 1;

Row row = table.AddRow();

row = table.AddRow();
row.Borders.Top.Width = 2;

PdfDocumentRenderer renderer = new PdfDocumentRenderer(true, PdfFontEmbedding.Always);
renderer.Document = document;
renderer.RenderDocument();

string filename = "TheBug.pdf";
renderer.PdfDocument.Save(filename);
Process.Start(filename);

The table contains two columns and two rows.
The two columns each have different borders on the left hand; I used a black 2px border for the first, and a red 1px border for the second column, so we can easily distinguish between them.

Then I added two rows, one without any changes, the other one with a top border been set. This is important, because changing any(!) border of a row causes the bug to occur.

--------

Now let's talk about the results. I expected the pdf to look like this:
Attachment:
withoutbug.PNG
withoutbug.PNG [ 895 Bytes | Viewed 3235 times ]

But in fact it looked like this:
Attachment:
withbug.PNG
withbug.PNG [ 1.15 KiB | Viewed 3235 times ]

So I downloaded the source and started to dig down, trying to find out what's wrong with this table.
I finally found the bug deep in the source of MigraDoc.DocumentObjectModel.Visitors\VisitorBase.cs

I have been using version 1.32 for bugfixing, but the bug appears in the latest 1.50 beta as well.
Please note this information, I can't guarantee that the line numbers are still valid for 1.50 beta.

---------

To eliminate the bug, open VisitorBase.cs, go to line 797 in the VisitTable-method.
Change:
Code:
if (cell.borders == null)
   cell.borders = row.borders;
else if (row.borders != null)
    FlattenBorders(cell.borders, row.borders);
if (cell.borders == null)
   cell.borders = column.borders;
else if (column.borders != null)
   FlattenBorders(cell.borders, column.borders);

to that:
Code:
if (row.borders != null)
   FlattenBorders(cell.Borders, row.borders);
if (column.borders != null)
   FlattenBorders(cell.Borders, column.borders);

The reason why, should be pretty obvious.
For example: In a row, where every cell's border has not been set (is null), 'cell.borders = row.borders;' is called for each cell in this row. Unfortunately, this will set the cell's border to a pointer of the row's border. Each cells border is now identical, so each cell looks the same.
In my case, I wanted the cells to get their border information from the corresponding columns, so I got the weird result.
I wonder why this hasn't already been discovered and fixed by someone.


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PostPosted: Thu Apr 23, 2015 1:32 pm 
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Joined: Mon Oct 16, 2006 8:16 am
Posts: 2953
Location: Cologne, Germany
Hi!
Thank you for your feedback.
Physikbuddha wrote:
I wonder why this hasn't already been discovered and fixed by someone.
This was fixed with 1.50 beta.
The bug was reported more than one year ago:
viewtopic.php?p=7835#p7835
At that time a workaround solved the issue for the user.

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Thomas Hoevel
PDFsharp Team


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PostPosted: Thu Apr 23, 2015 1:34 pm 
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Joined: Thu Apr 23, 2015 11:50 am
Posts: 2
As I wrote, I've installed v1.50 with the NuGet console and the bug still occurs.
Quote:
PM> Install-Package PDFsharp-MigraDoc-WPF -IncludePrerelease
"PDFsharp-MigraDoc-WPF 1.50.3638-beta" wird installiert.
"PDFsharp-MigraDoc-WPF 1.50.3638-beta" wurde erfolgreich installiert.
"PDFsharp-MigraDoc-WPF 1.50.3638-beta" wird hinzugefügt.
"PDFsharp-MigraDoc-WPF 1.50.3638-beta" wurde erfolgreich hinzugefügt.

Ran my code again, still the same bugged result. :(


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nuget.PNG
nuget.PNG [ 29.68 KiB | Viewed 3231 times ]
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PostPosted: Thu Apr 23, 2015 1:53 pm 
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PDFsharp Guru
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Joined: Mon Oct 16, 2006 8:16 am
Posts: 2953
Location: Cologne, Germany
Physikbuddha wrote:
As I wrote, I've installed v1.50 with the NuGet console and the bug still occurs.
You're right. It was fixed after 1.50 beta was published.

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Thomas Hoevel
PDFsharp Team


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