How to be notified on dragEnterEvent?

[tuxit]

Hello,

I have a custom type called polygon, which is a subcalss of QDeclarativeItem.

I want to be notified when a mouse clicked out of it, then dragged into it, (before mouse released!!!).

I have found out that QDeclarativeItem(super class of my custom type) has a function: dragEnterEvent.

I can override it in C++ class, but then everything will be all in C++.

I want to ask if it is possible to write something like

Polygon {
         id: aPolygon
         anchors.centerIn: parent
         width: 100; height: 100
         name: "A simple polygon"
         color: "blue"
         vertices:[
 
         Point{x:20.0; y:40.0},
         Point{x:40.0; y:40.0},
         Point{x:20.0; y:20.0}
         ]
 
         dragEnterEvent: aPolygon.doSomething
 
 
     }

Polygon {
         id: aPolygon
         anchors.centerIn: parent
         width: 100; height: 100
         name: "A simple polygon"
         color: "blue"
         vertices:[

         Point{x:20.0; y:40.0},
         Point{x:40.0; y:40.0},
         Point{x:20.0; y:20.0}
         ]

         dragEnterEvent: aPolygon.doSomething


     }

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How can it be possible? Using mouse area, but it does not have dragEnterEvent. How can i do this?
Thanks for any idea.

[laszlo.gosztola]

Hi!

Try to create a signal at C++ side and a handler on QML side with on prefix.
Like this:
c++
signals:
void dragStarted();

QML:
onDragStarted()

http://doc.qt.nokia.com/4.7-snapshot/qml-extending.html

[tuxit]

Hi, thanks for reply.
I tried to add signal but could not run.

Here is my polygon.cpp code:

#include "polygon.h"
#include "point.h"
#include <QPainter>
#include <stdio.h>
#include <iostream>
#include <sstream>
#include <QGraphicsSceneDragDropEvent>
#include <QFocusEvent>
#include "DeclarativeDragDropEvent.h"
 
using namespace std;
using namespace Qt;
 
Polygon::Polygon(QDeclarativeItem *parent)
    : QDeclarativeItem(parent)
{
    // need to disable this flag to draw inside a QDeclarativeItem
    setFlag(QDeclarativeItem::ItemHasNoContents, false);
    setFlags(ItemIsSelectable|ItemIsMovable|ItemIsFocusable);
    setAcceptDrops(true);
 
 
}
QVariant Polygon::itemChange(GraphicsItemChange change, const QVariant &value)
{
 
    return QGraphicsItem::itemChange(change, value);
}
 
 
void Polygon::focusInEvent ( QFocusEvent * event ){
    cout<<"focusin"<<endl;
}
 
QRectF Polygon::boundingRect() const{
 
    QVector<QPointF> vPnt=listToVector(m_vertices);
    return QPolygonF(vPnt).boundingRect();
 
}
 
QPainterPath Polygon::shape () const
{
    QPainterPath path;
    QVector<QPointF> vPnt=listToVector(m_vertices);
    path.addPolygon(QPolygonF(vPnt));
return path;
}
...
 
void Polygon::paint(QPainter *painter, const QStyleOptionGraphicsItem *, QWidget *)
{
    QPen pen(m_color, 2);
    painter->setPen(pen);
    painter->setRenderHints(QPainter::Antialiasing, true);
 
 
QVector<QPointF> vPnt=listToVector(m_vertices);
    painter->setBrush(QBrush(m_color,Qt::SolidPattern));
    painter-> drawPolygon(QPolygonF(vPnt),Qt::OddEvenFill);
 
 
 
}

#include "polygon.h"
#include "point.h"
#include <QPainter>
#include <stdio.h>
#include <iostream>
#include <sstream>
#include <QGraphicsSceneDragDropEvent>
#include <QFocusEvent>
#include "DeclarativeDragDropEvent.h"

using namespace std;
using namespace Qt;

Polygon::Polygon(QDeclarativeItem *parent)
    : QDeclarativeItem(parent)
{
    // need to disable this flag to draw inside a QDeclarativeItem
    setFlag(QDeclarativeItem::ItemHasNoContents, false);
    setFlags(ItemIsSelectable|ItemIsMovable|ItemIsFocusable);
    setAcceptDrops(true);


}
QVariant Polygon::itemChange(GraphicsItemChange change, const QVariant &value)
{

    return QGraphicsItem::itemChange(change, value);
}


void Polygon::focusInEvent ( QFocusEvent * event ){
    cout<<"focusin"<<endl;
}

QRectF Polygon::boundingRect() const{

    QVector<QPointF> vPnt=listToVector(m_vertices);
    return QPolygonF(vPnt).boundingRect();

}

QPainterPath Polygon::shape () const
{
    QPainterPath path;
    QVector<QPointF> vPnt=listToVector(m_vertices);
    path.addPolygon(QPolygonF(vPnt));
return path;
}
...

void Polygon::paint(QPainter *painter, const QStyleOptionGraphicsItem *, QWidget *)
{
    QPen pen(m_color, 2);
    painter->setPen(pen);
    painter->setRenderHints(QPainter::Antialiasing, true);


QVector<QPointF> vPnt=listToVector(m_vertices);
    painter->setBrush(QBrush(m_color,Qt::SolidPattern));
    painter-> drawPolygon(QPolygonF(vPnt),Qt::OddEvenFill);



}

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Here is main.qml code:

import MyTypes 1.0
import QtQuick 1.0
import Qt 4.7
 
 Item {
     id:container
     width: 300; height: 200
 
     Polygon {
         id: aPolygon
         anchors.centerIn: parent
         width: 100; height: 100
         name: "A simple polygon"
         color: "blue"
         vertices:[
 
         Point{x:20.0; y:40.0},
         Point{x:40.0; y:40.0},
         Point{x:40.0; y:20.0},
         Point{x:20.0; y:20.0}
         ]
 
 
     }
}

import MyTypes 1.0
import QtQuick 1.0
import Qt 4.7

 Item {
     id:container
     width: 300; height: 200

     Polygon {
         id: aPolygon
         anchors.centerIn: parent
         width: 100; height: 100
         name: "A simple polygon"
         color: "blue"
         vertices:[

         Point{x:20.0; y:40.0},
         Point{x:40.0; y:40.0},
         Point{x:40.0; y:20.0},
         Point{x:20.0; y:20.0}
         ]


     }
}

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I can see a polygon, but why focusInEvent is not called?
As you can see, i override boundingRect ans shape but no result.
I was doing nearly same things in Qt with C++ without QML.
Thanks for any idea.

[laszlo.gosztola]

Hello,

maybe we have some misundersanding.
I thought, You want to notify the QML side about a signal which happened at c++ side.

For an example of this, define a new signal in your header file, and in the cpp file somewher emit this signal.

e.g. in poligon.h

public slots:
  void testSignal();

public slots:
  void testSignal();

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in poligon.cpp somewhere

emit testSignal();

emit testSignal();

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in the qml file

Polygon {
  ....
  onTestSignal: {
    console.log("TestSignal was emitted")
  }
}

Polygon {
  ....
  onTestSignal: {
    console.log("TestSignal was emitted")
  }
}

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it's important, that the signal is lowercase in the header, but go to uppercase when gets the 'on' prefix

[tuxit]

hi,
your post is so useful but i have given up to try

onFocusIn:{ //something}

onFocusIn:{ //something}

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in QML side. It is the later problem.

for the moment, i only want my focusInEvent and focusOutEvent in polygon.cpp to be called when i click the polygon shape on QML viewer.

I succeed to make focusInEvent work by

void Polygon::mousePressEvent(QGraphicsSceneMouseEvent *event)
{
    forceActiveFocus();
}

void Polygon::mousePressEvent(QGraphicsSceneMouseEvent *event)
{
    forceActiveFocus();
}

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but now the problem have changed. focusOutEvent is not called when i click out of polygon.
And i could not find a mouseOutEvent.

If focusOutEvent do not work why it is there?

[laszlo.gosztola]

Ok, but it's the another direction.

Read FocusScope documentation in QML doc.
You can try something like:

FocusScope {
id: scope 
  Polygon {
    id: poly
    focus = true
}
}

FocusScope {
id: scope 
  Polygon {
    id: poly
    focus = true
}
}

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But as far as I know, focus is for keyboard handling. So why do You mix it with mouse handling?

[tuxit]

i was able to do what i want when i was working with Qt (without QML) and focusInEvent was working as i expected but in QML does not work. Anyway i will try FocusScope, but now i have another problem. Thanks