[pdftex] Adobe Battles Backward-Compatibility Woes

[Ross Moore]

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  
Javascript.

If Javascript is not enabled, then you want this new button to be  
inactive,
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  
mouse-click
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  
easily
by simply changing the order of the object references in an /Annots  
list.
This is a simple edit that doesn't change any byte-counts.

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


Cheers,

	Ross


> Hans
> -----------------------------------------------------------------
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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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