Feature request: table of contents generation without requiring to know in advance how many pages it will span

[alallier]

With this exception

fpdf.errors.FPDFException: The rendering function passed to FPDF.insert_toc_placeholder triggered to many page breaks: page 9 was reached while it was expected to span only 1 pages

Although I checked the code here and it doesn't seem it should fail

[alallier]

I was looking at the code and I see in the placeholder arguments you can specify how many pages it will span. This seems to work although you need to know your page count ahead of time which is impossible to do when running against dynamic datasets.

[Lucas-C]

Yeah, this a current limitation of this implementation.

I think I see how I can make this fully dynamic now, I'm going to have a look at it.

[Lucas-C]

Without knowing in advance how many page the ToC will span, we will have to shift page numbers according to its size once rendered.

The challenge will then be to increment all references to page numbers:

• in self.pages : dict containing pages and metadata
• in self.annots : link & text annotations
• in self.links : internal links inside the document
• in self.struct_builder.doc_struct_elem.k (all page.id)
• in self._outline

I fear this will introduce quite some code, and lower code readability...

As a workaround for now, you can always generate your documents with increasing values of pages passed to .insert_toc_placeholder, and stop when you do not have raised any exception.
It's an ugly approach, but it should work I think.

[jwinkel13]

A workaround would be to estimate the # of pages if the estimate is off one can use the # of pages the error returns to set the correct number. It allows for a max of 2 iteration

[yaminle]

If there is still any interest in this topic: Did an implementation of that. A little bit hacky though:

1. create the ToC at the end of the pdf
   -- use placeholders for the current page-numbers (like number of pages -> {nb})
2. reorder the pages and put the ToC in place
3. fix the links
4. replace the placeholders
   -- with the same limitations as the replacement of {nb}

I think that this could well be included in the current implementation