Re: [Libaps-general] Using libAPS in KDE

[Waldo B. <ba...@kd...>]

On Tue, 13 Jun 2000, you wrote:
> Waldo,
>
> > I'm working on migrating KDE 2.x to a APS based printing solution. As
> > such I have added v1.0 of libaps to kdesupport. Since it needs to write
> > to /etc it needs to be root so I haven't made it install by default. So
> > you need to pass --with-aps when configuring kdesupport.
>
> Suffice it to say that I'm very interested in what you're doing here, and
> what you have in mind. Is any of your code available (e.g. committed) yet,
> or are you still working on it locally?
>
> Brian

See below for what I have in mind :-) I have some code which I will commit to 
kdelibs/kprint this afternoon. It doesn't do much yet though.

Cheers,
Waldo

RFC: Printing in KDE 2.0
========================
Date: May 22, 2000
Author: Waldo Bastian

Printing support in KDE has not been changed since KDE 1.1.2. As such
it is not completely up to spec with the rest of KDE 2.0. In this document 
a printing architecture for KDE 2.0 is proposed.

Requirements
============

Four different desired printing related abilities can be identified 
within KDE:

1) The ability of a user to select a printer from the list of installed 
printers to be used for a print request and to select, possibly 
application specific, options for the print request.

2) The ability of a user to be notified of the status of his outstanding
print requests and the ability for the user to cancel outstanding print
requests.

3) The ability of an application to query the properties of the printer
used for a certain print request as well as options specified by the user
for this specific print request.

4) The ability of a user to add and configure a printer.


Status in KDE 1.1.2
===================

Ad 1) QPrintDialog provides this functionality in KDE 1.1.2. The drawbacks 
are that this dialog does not fit in well with the KDE translation meachanism
and that it is not possible to add application specific options to this 
dialog.

Ad 2) In KDE 1.1.2 applications exists which provide this functionality. The 
user has to start these applications explicitly. There is no integration
with the application that issued the print-request.

Ad 3) The QPrinter class provides basic information about the printer and
the specific print request, mostly based on information supplied by the user.

Ad 4) KDE 1.1.2 provides no way to do this.

Proposed KDE 2.0 printing architecture
======================================

I suggest to adopt sysAPS as API to access the operating systems printing 
system, e.g. CUPS or LPR:

KDE -> sysAPS -> IPP -> CUPS -> filters -> driver -> backend
              -> LPR -> filters -> driver -> backend

Other printing systems can be supported by adding support for them to sysAPS.

To quote the sysAPS homepage:

"This project, driven by Corel, provides a unified API for accessing 
printing-specific services outside the realm of the graphics API. This 
includes querying & controlling features of a given printer model, sending 
jobs, accessing queues and configuration."

sysAPS is under LGPL, is written in C and has both a C as well as an optional 
C++ API. It is a rather young project so it should not be a problem to adapt 
to any specific wishes in the API. You can find them at 
http://sourceforge.net/project/?group_id=2328.

Based on sysAPS it will be relatively straightforward to meet KDEs printing
requirements:

1) A KPrintDialog based on KDIalogBase should be made. It can use sysAPS
to query for available printers and enable/disable available options
based on the capabilities of the selected printer.

2) A notification/control interface should be made for printing job-control.
sysAPS seems to provide all necassery functionality. We only need to provide
the UI. Maybe this can be part of kio_uiserver. Maybe it should be made a
seperate application.

3) For now the QPrinter class seems to be adequate. It might be desirable to
embed this class in a KPrinter class to make it possible to add KDE wide
options not provided by Qt. In addition this class could give access to 
a printer's PPD file allowing applications to fine tune their print output.

4) A kcontrol module should be written which allows printer configuration.
sysAPI seems to provided al necassery functionality. Only the GUI part needs
to be added.


Considerations
==============

*) The proposed printing architecture is not limited to Postscript output, 
although that is what the Qt printing classes produce.

*) The proposed sysAPS library can be used by non-KDE applications, including
command line tools. Although the GNOME project is not interested in
cooperation in this area, there are no compelling technical reasons which 
prevent them from adopting sysAPS, now or in the future.


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