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1. Re: Form XObjects without Resources - do we ignore ancestor forms?
First – the version of the PDF spec you are using is VERY OLD. You should be using the international standard – ISO 32000-1:2008 as it is the official document at this time.
Second – the topic you raise has come up many times on the ISO committee and how to clean up and clarify that section. You will find the version in 32000 much clearer and more specific on how to handle it. Which is that if there is no Resources dictionary at all – then you inherit. If there is a Resources dictionary, then regardless of whether it has fonts (in your case), you do not inherit.
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2. Re: Form XObjects without Resources - do we ignore ancestor forms?
Thanks for that. The PDF that prompted this query was version 1.3, so I thought it would be best to refer to that version of the spec. Does the ISO spec relate to all versions or just the later ones?
I'll see if we can get access to it, I don't currently have a copy.
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3. Re: Form XObjects without Resources - do we ignore ancestor forms?
I take issue with "We should therefore get a missing font error as the PDF is invalid". If a PDF is invalid (as it would be) the behaviour is undefined. Unless you are using software that claims to be a complete PDF validator, the PDF reader may take any behaviour and would be correct, including
- an error
- a default font
- missing text
- looking at the chain of form XObjects
A PDF creator should of course only make correct PDFs rather than rely on accidental or deliberate permissiveness in any particular viewer.
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4. Re: Form XObjects without Resources - do we ignore ancestor forms?
Yes I'll agree with that, what I really meant is we shouldn't be surprised if we get errors. I work a lot with printers and generally I'm happier if a printer just fails and gives me a chance to fix the file myself, rather than guessing what to do.
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5. Re: Form XObjects without Resources - do we ignore ancestor forms?
Me too. I should also note that many utilities will not respect inheritance from page object if they do certain transformations such as convert a page to a form XObject (e.g. for placing as a graphic). I just point this out in case, in future, anyone reading this sees a shortcut and is tempted.
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6. Re: Form XObjects without Resources - do we ignore ancestor forms?
Yes, that's what prompted this question. We use a fairly popular PDF library to reorder and combine documents from various files. The original Page becomes a Form and the Resources inheritance ends up like my question. It doesn't attempt to add the 'missing' Resources to fix it up (can't really blame them).