PDF content not visible (white/empty view)

[GerHobbelt]

As reported by Tiffany here: https://getsatisfaction.com/qiqqa/topics/pdf-content-not-visible

I am using v. 78. I have a large library. Many of my pdfs display perfectly but some do not. If I have over the document, I still get the quick view. However, when I open the document none of the pages display, nor are they visible in the preview tab. The documents open fine in an external viewer.

Related issue report: https://getsatisfaction.com/qiqqa/topics/pdfs_stop_displaying_blank_pages

[GerHobbelt]

This is still an issue in v79 (last non-open-sourced release).

It is unclear to me if it's all due to a single cause or multiple causes.

Some of the (possible) reasons why

№ 1: protected PDF

One of the reasons Qiqqa will show a blank slate for an otherwise correctly imported PDF is when that PDF is flagged as protected. Many datasheets published in PDF format exhibit this behaviour once imported in Qiqqa.

As part of the Qiqqa reverse engineering work done in the years past (https://github.com/GerHobbelt/qiqqa-revengin), it turned out that taking those PDFs and deprotecting them using an external tool such as qpdf helps: this does (of course) NOT resolve the issue itself but the deprotected PDF will show up all right in Qiqqa once that one has been imported as well, thus providing a reasonable work-around. (https://github.com/GerHobbelt/qiqqa-revengin/blob/master/mv_protected_pdf.sh)

Examples of protected PDFs which cause this: On-Semi/Fairchild datasheets. (It's been long since I had this problem myself, so no ready example available straight away at the time of this writing, alas)

№ 2: bad or broken PDF imported into Qiqqa

When you use the Qiqqa Sniffer to find and download additional publications, once in a while a download MAY fail in such a way that Qiqqa believes a file has been obtained, but only part of the data has actually arrived (or even nothing at all): this will cause a bad/broken PDF file to be imported into Qiqqa, which will not be reported as broken or damaged, but instead will show up a a document with 1 or many utterly blank pages.

№ 3: ...

(Anything else from the discussion board?...)

[GerHobbelt]

Related to #34

[GerHobbelt]

An example PDF which exhibits this behaviour:
F7D042DAF56686EFEADFA1EDED8B5E9CCEE3C364.pdf

[GerHobbelt]

This is due to the Sorax library not handling certain PDFs.

See also #209

AFAICT this bug doesn't exit in MuPDF, at least not in the same form. Keeping this one open until #209 is done, as it's a known issue and a nauseating one.

[GerHobbelt]

See #209. This was a SORAX-specific bug. As bleeding edge now has kicked out SORAX, this problem at least is gone.

[GerHobbelt]

Afterparty Note: this bug is SORAX barfing a hairball ona whole slew of PDFs, particularly ones that are "protected" against printing, etc. OnSemi IC datasheets are a prime example: they failed all of them. MuPDF has no problem with them, so preprocessing these PDFs with qpdf before importing into Qiqqa is not needed any longer.