Definitively QScrollArea doesn't want work. I need help.

[franco.amato]

Hi, I'm becoming crazy with my customwidget.
I would write a widget that can grow orizontally and not vertically. ( fixed height and expanding width ) and I would attach a QScrollArea to it.
Well it don't work nothing.
My app inherits from QMainWidget and I do all in the centralwidget. ( in the central widget I would have 2 custom widget that's are WaveForm visualizer.

To test I add only one and it doesn't work.

Here the code:

CentralWidget::CentralWidget( QWidget* parent /* = 0 */ ) 
: QWidget(parent),
  m_pVbox( 0 ),
  m_pWaveU( 0 )
{
	/* vertical layout */
	m_pVbox = new QVBoxLayout( this );
 
	/* scroll area */
	saU = new QScrollArea( this );
 
	saU->setWidgetResizable( true );
 
	saU->setVerticalScrollBarPolicy( Qt::ScrollBarAlwaysOff );
 
	/* waveform */
	m_pWaveU = new WaveDisplay( saU );
 
	m_pWaveU->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
	m_pWaveU->setMinimumSize( QSize(1000, 200) );
 
	saU->setWidget( m_pWaveU ); 
 
       m_pVbox->addWidget( saU );
       QScrollBar *scrollBar = saU->horizontalScrollBar();
      scrollBar->setSliderDown( true );
 
      m_pVbox->addWidget( saU );
 
     setLayout(m_pVbox);
}

CentralWidget::CentralWidget( QWidget* parent /* = 0 */ ) 
: QWidget(parent),
  m_pVbox( 0 ),
  m_pWaveU( 0 )
{
	/* vertical layout */
	m_pVbox = new QVBoxLayout( this );

	/* scroll area */
	saU = new QScrollArea( this );

	saU->setWidgetResizable( true );

	saU->setVerticalScrollBarPolicy( Qt::ScrollBarAlwaysOff );

	/* waveform */
	m_pWaveU = new WaveDisplay( saU );

	m_pWaveU->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
	m_pWaveU->setMinimumSize( QSize(1000, 200) );

	saU->setWidget( m_pWaveU ); 

       m_pVbox->addWidget( saU );
       QScrollBar *scrollBar = saU->horizontalScrollBar();
      scrollBar->setSliderDown( true );
   
      m_pVbox->addWidget( saU );

     setLayout(m_pVbox);
}

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I have lots of problems with this code:

1. If I set

   QSizePolicy::Fixed

   QSizePolicy::Fixed

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   for the vertical size the widget is not shown
2. The scroll bar is only displayed when I resize the widget at the minimum size
3. If I draw outsize the visible part of the widget I can not see what I displayed. The scrollbar doesn't allow me to see the graph

And other, if I call resize( w, h ) inside the widget, it's not resized. The width() routine give to me always the same value.
i'm really confused. Is 1 month that I try to do this work without any success.
I'll be very happy to get some help from this mailing list.

Best Regards,
Franco

[faldzip]

Hi, I'm becoming crazy with my customwidget.

So I think that your custom widget code would be more interesting to see if it is there what you done wrong.
Especially how your sizeHint() method looks like?

EDIT:
Consider this example:

#include <QtCore>
#include <QtGui>
 
class Widget : public QWidget
{
	Q_OBJECT
public:
	Widget(QWidget *parent = 0);
	QSize sizeHint() const;
	void paintEvent(QPaintEvent *pe);
private slots:
	void slotClicked();
private:
	QPushButton *m_button;
	QSize m_size;
};
 
Widget::Widget(QWidget *parent)
	: QWidget(parent)
{
	m_size = QSize(200, 80);
	QHBoxLayout *lo = new QHBoxLayout;
	m_button = new QPushButton("Button", this);
	lo->addWidget(m_button);
	connect(m_button, SIGNAL(clicked()), this, SLOT(slotClicked()));
}
 
void Widget::paintEvent(QPaintEvent *pe)
{
	QWidget::paintEvent(pe);
	QPainter p(this);
	p.drawRect(QRect(0, 0, m_size.width()-1, m_size.height()-1));
}
 
QSize Widget::sizeHint() const
{
	return m_size;
}
 
void Widget::slotClicked()
{
	m_size.setWidth(m_size.width() + 100);
	updateGeometry();
	update();
}
 
int main(int argc, char **argv)
{
	QApplication a(argc, argv);
	QScrollArea sa;
	sa.setWidgetResizable(true);
	sa.setWidget(new Widget(&sa));
	sa.widget()->setSizePolicy(QSizePolicy::Minimum, QSizePolicy::Fixed);
	sa.show();
	return a.exec();
}
 
#include "main.moc"

#include <QtCore>
#include <QtGui>

class Widget : public QWidget
{
	Q_OBJECT
public:
	Widget(QWidget *parent = 0);
	QSize sizeHint() const;
	void paintEvent(QPaintEvent *pe);
private slots:
	void slotClicked();
private:
	QPushButton *m_button;
	QSize m_size;
};

Widget::Widget(QWidget *parent)
	: QWidget(parent)
{
	m_size = QSize(200, 80);
	QHBoxLayout *lo = new QHBoxLayout;
	m_button = new QPushButton("Button", this);
	lo->addWidget(m_button);
	connect(m_button, SIGNAL(clicked()), this, SLOT(slotClicked()));
}

void Widget::paintEvent(QPaintEvent *pe)
{
	QWidget::paintEvent(pe);
	QPainter p(this);
	p.drawRect(QRect(0, 0, m_size.width()-1, m_size.height()-1));
}

QSize Widget::sizeHint() const
{
	return m_size;
}

void Widget::slotClicked()
{
	m_size.setWidth(m_size.width() + 100);
	updateGeometry();
	update();
}

int main(int argc, char **argv)
{
	QApplication a(argc, argv);
	QScrollArea sa;
	sa.setWidgetResizable(true);
	sa.setWidget(new Widget(&sa));
	sa.widget()->setSizePolicy(QSizePolicy::Minimum, QSizePolicy::Fixed);
	sa.show();
	return a.exec();
}

#include "main.moc"

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You can experiment with size policy (read the documentation carefully about QSizePolicy::Policy) with reimplementing minimumSizeHint() and so on...