QgsRectangle QgsMapSettings::computeExtentForScale( const QgsPointXY &point, double scale, const QgsCoordinateReferenceSystem &sourceCrs ) const
{
QgsPointXY center = QgsCoordinateTransform( sourceCrs, destinationCrs(), mTransformContext ).transform( point );
// Output width in inches
double outWIn = outputSize().width() / double( outputDpi() );
// Desired visible width (honouring scale)
double scaledWIn = outWIn * scale;
if ( mapUnits() == QgsUnitTypes::DistanceDegrees )
{
// Start with an 1x1 extent around the center
QgsRectangle ext( center.x() - 0.5, center.y() - 0.5, center.x() + 0.5, center.y() + 0.5 );
// Get scale at extent, and then scale extent to the desired scale
double testScale = mScaleCalculator.calculate( ext, outputSize().width() );
ext.scale( scale / testScale );
return ext;
}
// Conversion from inches to mapUnits
double conversionFactor = 12 * QgsUnitTypes::fromUnitToUnitFactor( QgsUnitTypes::DistanceFeet, mapUnits() );
double delta = 0.5 * scaledWIn * conversionFactor;
return QgsRectangle( center.x() - delta, center.y() - delta, center.x() + delta, center.y() + delta );
}
void QgsMapSettings::setMagnificationFactor( double factor )
{
double ratio = mMagnificationFactor / factor;
mMagnificationFactor = factor;
double rot = rotation();
setRotation( 0.0 );
QgsRectangle ext = visibleExtent();
ext.scale( ratio );
mRotation = rot;
mExtent = ext;
mDpi = outputDpi() / ratio;
updateDerived();
}