QGraphicsItem *GridLineFactory::ellipseItem (const Transformation &transformation,
double radiusLinearCartesian,
const QPointF &posStartScreen,
const QPointF &posEndScreen) const
{
// LOG4CPP_INFO_S is below
QPointF posStartGraph, posEndGraph;
transformation.transformScreenToRawGraph (posStartScreen,
posStartGraph);
transformation.transformScreenToRawGraph (posEndScreen,
posEndGraph);
// Get the angles about the origin of the start and end points
double angleStart = posStartGraph.x() * DEGREES_TO_RADIANS;
double angleEnd = posEndGraph.x() * DEGREES_TO_RADIANS;
if (angleEnd < angleStart) {
angleEnd += TWO_PI;
}
double angleSpan = angleEnd - angleStart;
// Get origin
QPointF posOriginGraph (0, 0), posOriginScreen;
transformation.transformLinearCartesianGraphToScreen (posOriginGraph,
posOriginScreen);
LOG4CPP_INFO_S ((*mainCat)) << "GridLineFactory::ellipseItem"
<< " radiusLinearCartesian=" << radiusLinearCartesian
<< " posStartScreen=" << QPointFToString (posStartScreen).toLatin1().data()
<< " posEndScreen=" << QPointFToString (posEndScreen).toLatin1().data()
<< " posOriginScreen=" << QPointFToString (posOriginScreen).toLatin1().data()
<< " angleStart=" << angleStart / DEGREES_TO_RADIANS
<< " angleEnd=" << angleEnd / DEGREES_TO_RADIANS
<< " transformation=" << transformation;
// Compute rotate/shear transform that aligns linear cartesian graph coordinates with screen coordinates, and ellipse parameters.
// Transform does not include scaling since that messes up the thickness of the drawn line, and does not include
// translation since that is not important
double ellipseXAxis, ellipseYAxis;
QTransform transformAlign;
createTransformAlign (transformation,
radiusLinearCartesian,
posOriginScreen,
transformAlign,
ellipseXAxis,
ellipseYAxis);
// Create a circle in graph space with the specified radius
QRectF boundingRect (-1.0 * ellipseXAxis + posOriginScreen.x(),
-1.0 * ellipseYAxis + posOriginScreen.y(),
2 * ellipseXAxis,
2 * ellipseYAxis);
GraphicsArcItem *item = new GraphicsArcItem (boundingRect);
item->setStartAngle (angleStart * RADIANS_TO_TICS);
item->setSpanAngle (angleSpan * RADIANS_TO_TICS);
item->setTransform (transformAlign.transposed ().inverted ());
return item;
}
