[pdftex] Adobe Battles Backward-Compatibility Woes

Ross Moore ross at ics.mq.edu.au
Wed Mar 15 23:10:08 CET 2006

Hi Hans,

On 16/03/2006, at 2:04 AM, Hans Hagen wrote:

> James Quirk wrote:
>> On Wed, 15 Mar 2006, Martin Schr�der wrote:
>>> On 2006-03-15 12:05:50 +0100, holop ferenc wrote:
>>>> seems like pdf will be the next html :)
>>>> sooner or later, welcome the pdf quirk mode :)
>> Some of us have been using PDF in ``quirk mode'' for quite some time!
>>> I pity everyone who has to maintain a pdf rendering application.
>>> If you follow the specs, your application will not work well in
>>> the real world (i.e. with "legacy documents" -- fonts are a
>>> constant source of trouble). Making it work in the real world is
>>> a constant challenge.
>> One way of handling "legacy documents" would be for Adobe to  
>> introduce
>> a system-hook whereby a PDF could be automatically filtered,  
>> before it is passed to a viewer. The idea being that the filter  
>> translates what
>> it finds into "compliant PDF," whatever that happens to be at
>> the time of viewing.
> Such filters have been around for a while: pdf/x cum suis  
> compliance can be tested in acrobat 6 and higher. Unless one messes  
> around with pdfliterals in uncontrolled ways, pdftex output is  
> rather well pdf/x compliant.

Yes, but James is talking about having a filter mechanism available
to the *viewer*, not at the *creator* level.

> A weak spot in pdf files can be tricky things with annotations and  
> javascripts and multi-media stuff; such (new) features have always  
> been unstable, subjected to subtle changes, etc. I normally tend to  
> not supporting things like that officially unless proven stable  
> (enough) which often means skipping at least one version (of pdf or  
> the viewer)

For example, I developed a mechanism for hacking LaTeX's \ref so that  
when the
target is a float (figure or table) then an image pops-up of the  
float contents
above the location of the reference.
It uses an extra button placed over the normal hyperlink anchor-text.
Then James and I developed a way to drag this image around, using  

If Javascript is not enabled, then you want this new button to be  
and a mouse-click to be passed to the underlying hyperlink.
This is indeed what happens in Adobe Reader.
However in Apple's Safari, which doesn't support Javascript, the  
is not passed through the over-lying inactive button --- even though its
tool-tip does appear.

While this can be regarded as an error in Safari, it could be fixed  
by simply changing the order of the object references in an /Annots  
This is a simple edit that doesn't change any byte-counts.

Having a 3rd-party-programmer-supplied filter that analysed enough of  
PDF to detect the problem and implement the fix *for this browser*,  
make my documents employing these pop-up features much more widely  



> Hans
> -----------------------------------------------------------------
>                                          Hans Hagen | PRAGMA ADE
>              Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
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>                                             | www.pragma-pod.nl
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Ross Moore                                         ross at maths.mq.edu.au
Mathematics Department                             office: E7A-419
Macquarie University                               tel: +61 +2 9850 8955
Sydney, Australia  2109                            fax: +61 +2 9850 8114

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