Adding Powerpoint notes slides

[maciejwie]

Requested feature

Presenter notes are a valuable part of a Powerpoint presentation and are worth extracting. Docling uses uses the python-pptx library for parsing Powerpoint pptx files, which supports reading from the presenter notes, and which are stored as notes slides. The code to read the notes is fairly trivial and could look something like:

class MsPowerpointDocumentBackend(DeclarativeDocumentBackend, PaginatedDocumentBackend):
[...]
    def walk_linear(self, pptx_obj, doc) -> DoclingDocument:
[...]
            # Handle notes slide
            if slide.has_notes_slide:
                notes_slide = slide.notes_slide
                notes_text = notes_slide.notes_text_frame.text.strip()
                if notes_text:
                    bbox = BoundingBox(l=0, t=0, r=0, b=0)
                    prov = ProvenanceItem(
                        page_no=slide_ind + 1, charspan=[0, len(notes_text)], bbox=bbox
                    )
                    doc.add_text(
                        label=DocItemLabel.TEXT,
                        parent=parent_slide,
                        text=notes_text,
                        prov=prov,
                    )

but I'm not sure how the core team would like to see provenance handled, since there is no bounding boxes to use but the model will not accept None. Should we use an empty bbox? How would you want something like this handled?

Alternatives

Since the python-pptx library used already supports this feature, no alternatives are necessary and it can be integrated as-is.