Identifying which label was clicked in qt - qt

Question

I have 10 Qlabels with an image on each. When i click on a label, its image should be cleared. I am able to identify which label was clicked theorotically, using the pixel clicked and size of each image. But how to use that information?
Eg. each label has dimension 100*100, the first label starting from 0,0. if pixel clicked is 250,50, i know that the third label was clicked, but how to use this to clear the label.
Im stuck.

Answer 1

There are a few ways how to implement it.
First. I would recommend to use a new class that inherits QLabel and overloads mouseReleaseEvent() handler where you just call clear() method. In this case the label will detect the mouse clicks itself and will clear its content internally.
class SelfClearingLabel : public QLabel
{
public:
using QLabel::QLabel;
protected:
void mouseReleaseEvent(QMouseEvent * event)
{
if (event->button()==Qt::LeftButton)
// process only clicks on the left button
{
clear();
}
QLabel::mouseReleaseEvent(event);
}
};
Second. You can catch mouseReleaseEvent() in your top widget and iterate over all of your child QLabel widgets and check which one is currently under mouse and clear the one. If you have other labels on this widget that shouldn't be cleared on mouse clicks then you can add some property to the QLabels that are under your interest.
void SomeTopFrame::createImageLabels(int count)
{
for (int i=0;i<count;i++)
{
QLabel* label=new QLabel(this);
label->setProperty("clear_on_click",true);
// assume that labels are added to layout *m_labelsLayout;
m_labelsLayout->addWidget(label);
}
}
void SomeTopFrame::mouseReleaseEvent(QMouseEvent * event)
{
if (event->button()==Qt::LeftButton)
// process only clicks on the left button
{
QList<QLabel*> labels=findChildren<QLabel*>();
foreach (QLabel* label, labels)
{
if (label->property("clear_on_click")&&label->underMouse())
{
label->clear();
break;
}
}
}
QFrame::mouseReleaseEvent(event);
}
It is a sample code just to show the principle. In production you can add a check that mouseReleaseEvent() is on the same widget as the mousePressEvent() to avoid triggering on drag and drop events.

Answer 2

Create the custom class that inherit QLabel :
ClickableLabel.h
class ClickableLabel : public QLabel
{
Q_OBJECT
public:
explicit ClickableLabel( const QString& text="", QWidget* parent=0 );
~ClickableLabel();
signals:
void clicked();
protected:
void mousePressEvent(QMouseEvent* event);
};
ClickableLabel.cpp
ClickableLabel::ClickableLabel(const QString& text, QWidget* parent)
: QLabel(parent)
{
setText(text);
}
ClickableLabel::~ClickableLabel()
{
}
void ClickableLabel::mousePressEvent(QMouseEvent* event)
{
emit clicked();
}
Just connect all labels clicked signal to following slot :
MyClass::labelClicked()
{
ClickableLabel *label = (ClickableLabel*)QObject::sender;
if(label)
label->clear();
}