Currently the QPrinter constructor, setOutputFormat() and
setPrinterName() make bad assumptions about the availability of printers
when configuring NativeFormat which can lead to inconsistent print
engine set-ups leading to crashes in the print dialog, especially on
Windows where a valid DEVMODE is needed.
This change cleans up the init and methods to ensure NativeFormat can
only ever be set if we have both a valid plugin and a valid printer,
if not the PdfFormat is used. One side-effect of this is that it is
now impossible to set an invalid printer name via QPrinter (but still
able to be done via QPrintEngine if really needed). Also if no
default printer is set then use the first available one.
This also fixes a bug where setting a new printer name on Windows
reset all the saved settings.
[ChangeLog][Important Behavior Changes] QPrinter no longer allows you
to set an invalid printer name.
Task-number: QTBUG-34345
Task-number: QTBUG-26008
Task-number: QTBUG-26430
Change-Id: I19737e4209d8c8df5817ea83246b3dd0c483ee85
Reviewed-by: Gunnar Sletta <gunnar.sletta@digia.com>
e8a45152b5