Delay the calculation of m_width and m_height (and all its associated things) until first time the widget is shown (paintEvent), doing KGlobalSettings::desktopGeometry(this); in PresentationWidget::PresentationWidget always returns the geometry of the first screen, so it must be done in paintEvent (for example), where the widget has already been shown and KGlobalSettings::desktopGeometry(this); returns the geometry of the correct screen.
Thanks to Olaf Bonorden for the patch testing
BUGS: 97347

svn path=/trunk/kdegraphics/kpdf/; revision=389970