How to create a custom Button?

[wysota]

Why don't you just subclass one of existing implementations of QAbstractButton like QCheckBox, QToolButton or QPushButton? You'd only need to reimplement the paint event... I guess even something like this would be enough:

class SwitchButton : public QCheckBox {
public:
  SwitchButton(QWidget *p=0) : QCheckBox(p){}
  QSize sizeHint() const{
    QString c = checkState()==Qt::Checked ? ":/mypixmap_checked.png" : ":/mypixmap_unchecked.png";
    return QPixmap(c).size();
  }
protected:
  void paintEvent(QPaintEvent *){
    QPainter p(this);
    QString c = checkState()==Qt::Checked ? ":/mypixmap_checked.png" : ":/mypixmap_unchecked.png";
    p.drawPixmap( QPixmap(c));
  }
}

class SwitchButton : public QCheckBox {
public:
  SwitchButton(QWidget *p=0) : QCheckBox(p){}
  QSize sizeHint() const{
    QString c = checkState()==Qt::Checked ? ":/mypixmap_checked.png" : ":/mypixmap_unchecked.png";
    return QPixmap(c).size();
  }
protected:
  void paintEvent(QPaintEvent *){
    QPainter p(this);
    QString c = checkState()==Qt::Checked ? ":/mypixmap_checked.png" : ":/mypixmap_unchecked.png";
    p.drawPixmap( QPixmap(c));
  }
}

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[jacek]

QString c = checkState()==Qt::Checked ? ":/mypixmap_checked.png" : ":/mypixmap_unchecked.png";
return QPixmap(c).size();

IMO it would be better to use QPixmapCache instead of loading those pixmaps every time they are needed.

[wysota]

IMO it would be better to use QPixmapCache instead of loading those pixmaps every time they are needed.

That's only an example, I wanted to make it as simple as can be. It would be enough to have two static QPixmap members in the class that would hold those pixmaps, I don't see a benefit from the cache here.

[jacek]

That's only an example, I wanted to make it as simple as can be.

But still, it's an improper example. You've just made it too simple.

It would be enough to have two static QPixmap members in the class that would hold those pixmaps, I don't see a benefit from the cache here.

How do you want to initialize static QPixmaps? QApplication instance must be created first.

[wysota]

But still, it's an improper example. You've just made it too simple.


How do you want to initialize static QPixmaps? QApplication instance must be created first.

Somehow I knew you would ask that question

class x{
static QPimxap *p1;
static QPixmap *p2;
public x(){
  if(!p1){
    p1 = new QPixmap(...);
    p2 = new QPixmap(...);
  }
}
};
 
QPixmap *x::p1 = 0;
QPixmap *x::p2 = 0;

class x{
static QPimxap *p1;
static QPixmap *p2;
public x(){
  if(!p1){
    p1 = new QPixmap(...);
    p2 = new QPixmap(...);
  }
}
};

QPixmap *x::p1 = 0;
QPixmap *x::p2 = 0;

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Of course this causes a slight memory leak if you don't count instances of your class. An alternative is to have those pixmaps directly in the class as regular members, only that it will have a bigger memory footprint.

BTW. It's not an improper example - you simply don't like it.

[jacek]

It's not an improper example - you simply don't like it.

It's just unnecessarily inefficient.

[jrideout]

I've been playing around with the new stylesheet thing and it makes everything much simpler. (The below is a stylesheet, not c++)

QCheckBox::indicator:unchecked {
    image: url(:/images/checkbox_unchecked.png);
}
 
QCheckBox::indicator:checked {
    image: url(:/images/checkbox_checked.png);
}

QCheckBox::indicator:unchecked {
    image: url(:/images/checkbox_unchecked.png);
}

QCheckBox::indicator:checked {
    image: url(:/images/checkbox_checked.png);
}

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This is implemented with qApp->setStyleSheet() globally or with myCheckbox->setStyleSheet() for a particular checkbox. Also, check out the Style Sheet Example