Unexpected results with KPrinter and QPaintDeviceMetrics

[Michael Goffioul]

Due to internal reasons, a synchronization step needs to be done between the
options set in the print dialog, and the internal PS generator (QPrinter).
This
corresponds to KPrinter::preparePrinting (which is protected). However, this
function is automatically called when calling QPainter::begin() on the
KPrinter
object. There's 2 solutions:

1) the normal one:

KPrinter printer;
if (printer.setup())
{
   QPainter painter(&printer);
   QPaintDeviceMetrics metrics(&printer);
   // you should now have the correct values
}

2) solution 1) is only valid if you intend to print something, which is
usually the
case. Indeed, QPainter::end() will send the PS to the selected printer. If
you
want to avoid that, the workaround is to inherits from KPrinter like this:

class MyPrinter : public KPrinter
{
public:
   // constructors, and so on
   void doPrepare() { preparePrinting(); }
   void doFinish() { finishPrinting(); }
}

and then:

MyPrinter printer;
printer.setup();
printer.doPrepare();
QPaintDeviceMetrics metrics(&printer);
// you should have the correct values

I plan to add such utility functions to the KPrinter API and add a mechanism
to avoid such problems, for 3.2.

Bye.
Michael.