Mouse event handling in rotated QQuickItem - qt

Question

I have a simple QQuickPaintedItem which draws a circular sector at a given position, with a given sector size and azimuth. Here is the header:
#pragma once
#include <QtQuick/QQuickPaintedItem>
#include <QColor>
#include <QPainter>
class MarkerItem : public QQuickPaintedItem
{
Q_OBJECT
Q_PROPERTY(QColor color READ color WRITE setColor)
Q_PROPERTY(int azimuth READ azimuth WRITE setAzimuth)
Q_PROPERTY(int sectorSize READ sectorSize WRITE setSectorSize)
Q_PROPERTY(QPointF anchorPoint READ anchorPoint WRITE setAnchorPoint NOTIFY anchorChanged)
Q_PROPERTY(bool selected READ selected WRITE setSelected NOTIFY selectedChanged)
public:
MarkerItem(QQuickItem *parent = nullptr);
QColor color() const;
void setColor(const QColor &color);
int azimuth() const;
void setAzimuth(int angle);
int sectorSize() const;
void setSectorSize(int span);
QPointF anchorPoint() const;
void setAnchorPoint(const QPointF &value);
bool selected();
void setSelected(const bool bVal);
public slots:
void mousePressEvent(QMouseEvent *event) override;
protected:
void paint(QPainter *painter) override;
private:
QColor mcColor;
int miAzimuth;
int miSectorSize;
QPointF mcAnchorPoint;
bool mbSelected;
const int miSectorRadius = 40;
signals:
void anchorChanged(QPointF);
void selectedChanged(bool);
};
and the implementation:
#include "markeritem.h"
#include <QSGGeometryNode>
#include <QtMath>
MarkerItem::MarkerItem(QQuickItem *parent)
: QQuickPaintedItem(parent)
{
setAcceptedMouseButtons(Qt::LeftButton);
qDebug() << "MarkerItem";
setWidth(qTan(qDegreesToRadians(30.0f))*40);
setHeight(40);
mbSelected = false;
}
void MarkerItem::paint(QPainter *painter)
{
qDebug() << " > MarkerItem paint, azimuth " << miAzimuth;
QPen pen;
QBrush brush(mcColor);
if (mbSelected)
{
pen.setColor(Qt::magenta);
pen.setWidth(2);
brush.setColor(mcColor.lighter(150));
}
else
{
pen.setColor(Qt::black);
pen.setWidth(1);
}
painter->setPen(pen);
painter->setBrush(brush);
painter->setRenderHints(QPainter::Antialiasing, true);
const QRectF rect = boundingRect();
setAnchorPoint(QPointF(rect.left()+rect.width()/2.0,rect.bottom()));
// we define a helper rectangle what we use to draw a pie,
// as the drawPie() method expect a rect, and the pie will start from the
// center of that rect
QRectF cPieRect(anchorPoint().x()-rect.height(), anchorPoint().y()-rect.height(),
rect.height()*2,rect.height()*2);
painter->drawPie(cPieRect,(90-miSectorSize/2)*16, miSectorSize * 16);
// drawing the bounding rectangle in red for visual debugging
QPen pen2(Qt::red,1);
painter->setPen(pen2);
painter->setBrush(QBrush(Qt::transparent));
painter->drawRect(rect);
setTransformOriginPoint(anchorPoint());
setRotation(miAzimuth);
}
// setters/getters
QPointF MarkerItem::anchorPoint() const
{
return mcAnchorPoint;
}
void MarkerItem::setAnchorPoint(const QPointF &value)
{
mcAnchorPoint = value;
emit anchorChanged(value);
}
void
MarkerItem::mousePressEvent(QMouseEvent *event)
{
qDebug() << "MarkerItem MousePressEvent" << event;
setSelected(!mbSelected);
}
bool
MarkerItem::selected()
{
return mbSelected;
}
void
MarkerItem::setSelected(const bool bVal)
{
if (bVal == mbSelected)
{
return;
}
mbSelected = bVal;
emit selectedChanged(mbSelected);
update();
}
QColor MarkerItem::color() const
{
return mcColor;
}
void MarkerItem::setColor(const QColor &acColor)
{
mcColor = acColor;
}
int MarkerItem::azimuth() const
{
return miAzimuth;
}
void MarkerItem::setAzimuth(int angle)
{
miAzimuth = angle;
}
int MarkerItem::sectorSize() const
{
return miSectorSize;
}
void MarkerItem::setSectorSize(int angle)
{
miSectorSize = angle;
}
And using it like:
import Marker 1.0 // this is the Markeritem class
import QtQuick 2.9
import QtQuick.Window 2.2
import QtQuick.Controls 1.4
Item
{
id: root
visible: true
width: 1800
height: 900
MarkerItem
{
id: m0
x: 900
y:450
color: "green"
azimuth: 0
sectorSize: 30
}
MarkerItem
{
id: m1
x: 900
y:450
color: "green"
azimuth: 120
sectorSize: 30
}
}
The QQuickPaintedItem defines a bounding rectangle which fits to the circular section to draw, and using QPainter's drawPie() method to draw the needed shape, after which by calling setRotate(), it rotates the item into the requested azimuth. I also need to handle the mouse click event to select/unselect an item. What i experience is that when the azimuth of an item is 0 (so it's not rotated), the mouse events of the bounding rectangle are received by my handler, but when the item is rotated, my item doesn't receive the mouse event from the area of the drawn item, but receives some of the mouse events outside from the bounding rectangle, from an area which seems to be at the point reflection of the original area, where the center is the anchorpoint (the tip if the circular sector, which is also the center of the rotation), but it's hard to define the area from which the events are delivered to my handler.
My assumption would be that with the "setRotation()" call, also the mouse area is rotating. Is there something I've overlooked? Is there any method to handle mouse events from a rotated item?
The item is supposed to use in a Map item via a MapQuickItem, but the issue is also reproducible without a Map item, so the map related parts are mostly omitted here.

Answer 1

setRotation() rotates the item so it should not be in paint since that method is called every time the item is painted, for example before the mouse event, in conclusion setRotation() should only be called in setAzimuth()
void MarkerItem::paint(QPainter *painter)
{
qDebug() << " > MarkerItem paint, azimuth " << miAzimuth;
QPen pen;
QBrush brush(mcColor);
if (mbSelected)
{
pen.setColor(Qt::magenta);
pen.setWidth(2);
brush.setColor(mcColor.lighter(150));
}
else
{
pen.setColor(Qt::black);
pen.setWidth(1);
}
painter->setPen(pen);
painter->setBrush(brush);
painter->setRenderHints(QPainter::Antialiasing, true);
const QRectF rect = boundingRect();
setAnchorPoint(QPointF(rect.center().x(),rect.bottom()));
// we define a helper rectangle what we use to draw a pie,
// as the drawPie() method expect a rect, and the pie will start from the
// center of that rect
QRectF cPieRect(anchorPoint().x()-rect.height(), anchorPoint().y()-rect.height(),
rect.height()*2,rect.height()*2);
painter->drawPie(cPieRect,(90-miSectorSize/2)*16, miSectorSize * 16);
// drawing the bounding rectangle in red for visual debugging
QPen pen2(Qt::red,1);
painter->setPen(pen2);
painter->setBrush(QBrush(Qt::transparent));
painter->drawRect(rect);
}
...
void MarkerItem::setAzimuth(int angle)
{
miAzimuth = angle;
setTransformOriginPoint(anchorPoint());
setRotation(miAzimuth);
}

Answer 2

OK, so turned out that the problem was with incorrectly setting the transform origin. I set the anchor point to the bottom center of the bounding rect as:
setTransformOriginPoint(anchorPoint());
where the anchor point was set earlier to
setAnchorPoint(QPointF(rect.center().x(),rect.bottom()));
If i set the transform origin explicitly to the bottom center of the item as:
setTransformOrigin(QQuickItem::Bottom);
It works as it should.