Be careful with QPainter::drawRect etc

[John Tapsell]

Hey all,

  I have tracked down a bugs in KFormula where the problem was that:

QPainterPath rect;
rect.addRect(0, -baseLine(), width(), baseLine() );
painter.drawPath( rect );

and

painter.drawRect(0, -baseLine(), width(), baseLine() );

Draw different rectangles.  The reason for this is that addRect takes
reals, and drawRect takes int.  The drawRect thus loses precision, and
draws incorrectly.

This is a very subtle and very nasty bug, as at 500% zoom, it's off by
less than 10 pixels typically.

I have grepped the koffice source code and found hundreds of uses of
drawRect, drawLine etc.  I'm sure that many of this are wrong.

Can we put a check for this use ebn?  There will be false positives,
but I think we need to check all uses of this.

(same for drawLine, etc)

John