RE: Future of DSSSL: What about PDF?

["Didier PH Martin" <martind@xxxxxxxxxxxxx>]

Hi Carlos

<YourComment>
As I understand the page-sequence FOs are not currently implemented by
Jade. Though, James has said, implementing the front end part of it
should be relatively easy, however no backend can currently support
the DSSSL page model.

Where can I get some examples on using the page-sequence FOs? It's
difficult for me to understand how they should work from the spec.
And since there are no tools to play with...

I thought about attempting to design such a formatter some time ago.
However, it's been only that, just an attempt!
One of the key points, of course,  is to implement the DSSSL
page model and the synchronization flow objects from the start,
then a simple-page-sequence would be implemented in terms of the
more general page-sequence. There's no gain on not implementing
the page model, we already have that.
However, after reading the spec several times about the page
model, I need some practical examples, to make sure I have
the correct interpretation.
</YourComment>

<Reply>
Me too, I am having difficulties to understand the page-sequence FO and
would be glad to get an example or someone giving me an example. Maybe,
because there isn't any, we can find some meaning by starting a discussion
thread on it.

I' tell you my understanding:

There is two page models:

a) window based  - the page is a window and the corresponding formatting
object is the scroll object. the document can be bigger than the window and
a scroll mechanism allows access to the document. This page model conform to
today's GUIs. The page could be seen as a huge paper roll :-)
b) page based - the page is a surface. this model could be emulated on GUIs
or based on a real paper substrate. The main distinction here is that the
page is limited in length and the whole document showned as page collection
intead of a single page model as with the scroll FO.

Both models provide margins or area around the text.

So, the page-simple-sequence FO fits case (b).

I'll read the specs on the scroll object to be sure, but I think that the
document width is limited by the window size and the document length is
unlimited. So the document could be longer than the window surface and a
scroll mechanism provides access to the whole document. The document width
is forced to fit in the window width by reformatting the content when the
window is resized. When the document length equal the window length (or I
should say window's height) then the scroll becomes optional even not
necessary and can be removed from the window's set of interactors. For
example HTML is based implicitely on a Scroll FO.

In the case of page based, each page has limited dimensions then the display
mechanism will show this page separation.

<Question>
I seems we have now this question, how do we emulate or show on paper a
simple-page-sequence. If we take "paper" surfaces, how would we model a
simple-page-sequence ?
</Question>

So, now let's find it. I'll read also the specs again and try an
explanation, write it, and if I am wrong we all find the right
interpretation :-) So, I'll do my homework and come back with an
explanation.

Do we all agree on the scroll versus page-xxx interpretation? so that we can
say that dsssl basic document presentation objects are of two kinds: GUI
based and represented by the scroll object (displayed in a window with the
rule previously mentioned) and "paper" based either on real paper surface or
emulated in a GUI. The former has documents seen as a big long "paper"
(imagine a very long paper). A window is used to see the document and  can
only see a portion of it. <Question> could the scroll object be larger than
the window or the document is always resized to fit in the window's
width?</Question>. The latter has pages with limited length. A page is then
a limited sized surface and not a big roll :-) When this model is emulated
on GUIs, the document is cut into several surfaces with limited length (not
a huge roll like the former). The scroll mechanism provides access to the
surface collection. Thus, the essential distinction between the former and
the latter is that the former (scroll) present the document as a whole and
the latter as a collection of pages.

I know this is basic, but it helps sometime to go back to the basics to
progress further.
<Reply>

Regards
Didier PH Martin
mailto:martind@xxxxxxxxxxxxx
http://www.netfolder.com


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