[Development] QtCS - Qt Printing Session Notes

[John Layt]

Apologies for the late posting.  The Qt Printing session consisted
mostly of a ramble by me on the current status and future plans,
followed by some discussion on areas of common interest.

Release status:

* Linux looking good, just some clean-ups and bug fixes in the print dialog
* Mac mostly good, but a blocker bug with fonts (see below)
* Windows not well tested but no known issues, focus in next few weeks

The Mac font bug is [1], with a possible root cause [2], a patch [3]
fixes the issue in printing but Eskil says this is the wrong solution.
 This is probably a blocker bug.

[1] https://bugreports.qt-project.org/browse/QTBUG-25555
[2] https://bugreports.qt-project.org/browse/QTBUG-25781
[3] https://codereview.qt-project.org/#change,25065

Testing:

* Some auto tests are still marked as insignificant due to failing
tests, but a test re-write is under way to fix this.
* Currently documenting a platform feature support matrix as part of this
* Testing printer info needs ability to add/remove virtual printers,
currently being developed
* We cannot automate testing physical output, need to write manual test plans
* Windows testing is a problem, I don’t build it very often, help sought

PDF Generator:

* Not sure who is really responsible, is spread between QtGui and QtPrintSupport
* Needs improvements, ideally to PDF/A standard as used in CUPS workflow
* Bug reports that files too big and text not searchable?
* Digia plan some fixes from customer requests
* Scribus said to have a good implementation, but CLA prevents us using it
* Expert help welcomed

Future Plans:

* QtPrintSupport mostly "done", but may be willing to add features
that don't require major API additions, such as extending support for
existing features onto more platforms
* Some high-level plans for new module on
http://qt-project.org/wiki/Qt-5-QtPrint
* Possibly a Tech Preview release in 5.1 with full release in 5.2,
depending on release cycle frequency
* Could have an entirely PDF/A based workflow, but for Windows which
would need a PDF to GDI conversion, Ghostscript too big to depend on
for this (how does Scribus do it?)
* Instead will still need to support native workflows, but need to
separate painting and print system more than currently.

Print filters:

* Ability to apply manipulations to PDF print file before printing,
such as poster and booklet
* Ideally options should be supported in Print System, i.e. CUPS, but
CUPS have no plans to do so
* On Windows is often built into the print driver so option in print dialog
* Unable to support on Windows or Mac native, but possible under Linux
and maybe Mac PDF
* Could ship a standard set with dialog options supporting them
* Could allow app to chain in own filters with config via adding tabs
* Might clash with the cups filters such as n-up,but could be smart about it
* Alternatively could have a QPagedDocument that implements them
cross-platform then paints that to native print format
* Advanced feature, keep in mind for a later release

Cheers!

John.