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Re: Packaging the new OpenPrinting project Common Print Dialog Backends

Hi,

I hope someone has read my posting from one month ago, cited below.
I have looked into how to package cpdb-libs and asked Nilanjana (the student who wrote this package) for some changes but she did not come around to do them. So I packaged the current GIT snapshot now. 

The source package is downloadable here, so that you can have a look:

http://www.openprinting.org/download/tmp/cpdb-libs_1.0+20171128-0ubuntu1.debian.tar.xz
http://www.openprinting.org/download/tmp/cpdb-libs_1.0+20171128-0ubuntu1.dsc
http://www.openprinting.org/download/tmp/cpdb-libs_1.0+20171128.orig.tar.gz
It works all well, but it has a little oddity: The source package provides two shared library, one named libcpdb-libs-backend, to be used by the print dialog backends and one named libcpdb-libs-frontend, to be used by the print dialogs. Under the binary packages generated are two packages providing the libraries and the two appropriate -dev packages. The two libraries also contain some helper functions in common, from lib/common_helper.c and described in the header common_helper.h. As these functions are linked into both libraries one would have to put common_helper.h into both -dev packages, but this would make them conflicting. Therefore I have created an additional libcpdb-libs-common-dev binary package and made the -dev pakages of both libraries depending on this one. 

Is this OK? Or have I to proceed in another way for this?

   Till

On 10/27/2017 01:58 PM, Till Kamppeter wrote:

Hi,
as you perhaps know we have started a new project in this year's Google Summer of Code. Five students have worked on a new concept to assure feature completeness, printing technology support, and maintainability of print dialogs.
A problem of desktop printing is that there are many different print dialogs, from different GUI toolkits like GTK and Qt but also from individual applications like LibreOffice or the Chromium Browser. Adding new print technologies (like Google Cloud Print) or new features to existing print technologies (like CUPS' new feature of auto-creating temporary queues for driverless IPP printers) always require changes on the print dialogs and due to the fact that they are often not well maintained and that the GUI toolkits have rather long release cycles the new technologies and features do not get supported by the print dialogs of desktop apps.
To overcome this we have introduced a concept of separating the print dialog's GUIs from the print dialog's communication with the printing systems using a frontend/backend concept with a D-Bus interface.
For each print technology (currently CUPS/IPP and Google Cloud Print, soon also save to PDF file) there is a GUI-toolkit-independent backend doing the communication with the printing system and providing a D-Bus API to the frontends (the print dialogs). A print dialog, when it is opened, first does a broadcast call into the D-Bus to find which backends are installed, then calls the list-printers function of each backend to get a list of all available printers. When the user selects a printer, the appropriate backend is asked for further capabilities of the printer (to build the printer options screen) and if the "Print" buttonis clicked, the PDF is sent to the selected printer via its backend.
To get it into Debian (and from there into Ubuntu) at first the GUI-toolkit independent parts needs to get packages. These are the following projects on the new OpenPrinting GitHub (https://github.com/OpenPrinting): 


cpdb-libs:

https://github.com/OpenPrinting/cpdb-libs

Frontend and Backend Libraries
These libraries allow for easy use of the D-Bus interface by print dialogs (frontends) and backends providing simple APIs so that the developer does not need to do the D-Bus communication directly. 


cpdb-backend-cups:

https://github.com/OpenPrinting/cpdb-backend-cups

CUPS/IPP Backend
This backend does all the communication with CUPS (and IPP printers) for listing printers and capabilities and sending off print jobs. Needs cpdb-libs. 


cpdb-backend-gcp:

https://github.com/OpenPrinting/cpdb-backend-gcp

Google Cloud Print Backend
This backend does all the communication with Google's servers for Cloud Print for listing printers and capabilities and sending off print jobs. Needs cpdb-libs.
These three projects need to be Debian-packaged in three source packages so that the GUI toolkits (GTK and Qt) and LibreOffice can get built with this functionality. LibreOffice has already adopted these changes to be included in their next release. GTK will have it in its next major release. Qt will probable include it in 5.10. An adaptor backend for using the Common Print Dialog Backends with current GTK's print dialog is in the works.
My plans are to introduce this new concept in Ubuntu 18.04 (Feature Freeze mid-February 2018). It would be great if the Debian packaging could be done soon so that I can sync it into Ubuntu. 

Thank you very much for any form of cooperation.

    Till
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