My custom widget don't appear in window.

[jiandingzhe]

This is my custom widget class:
@
class GenoEyeWidget : public QWidget
{
Q_OBJECT
public:
explicit GenoEyeWidget(double page_w, double page_h,
geno_eye::PosType genome_display_length,
QWidget* parent = 0, Qt::WindowFlags f = 0);
protected:
virtual void paintEvent(QPaintEvent* e);
//......
};

GenoEyeWidget::GenoEyeWidget(double page_w, double page_h,
geno_eye::PosType genome_display_length,
QWidget* parent, Qt::WindowFlags f) :
QWidget(parent, f),
//......
{
// ......
resize(page_w, page_h);
setSizePolicy(QSizePolicy::Fixed, QSizePolicy::Fixed);

qDebug() << "size on construction:" << this->size() ;
// ......

}
void GenoEyeWidget::paintEvent(QPaintEvent* e)
{
qDebug() << "on paint event";
//......
}
@
and this is the test code:
@
class t_genoeyewidget : public QMainWindow
{
friend int main(int argc, char** argv);
Q_OBJECT

public:
explicit t_genoeyewidget(QWidget *parent = 0);
~t_genoeyewidget();

private:
Ui::t_genoeyewidget *ui;
};

t_genoeyewidget::t_genoeyewidget(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::t_genoeyewidget)
{
ui->setupUi(this);

GenoEyeWidget* content = new GenoEyeWidget(400, 600, 1000);
ui->scrollArea->setWidget(content);

}

t_genoeyewidget::~t_genoeyewidget()
{
delete ui;
}

int main(int argc, char** argv)
{
QApplication app(argc, argv);

t_genoeyewidget mw;
mw.show();
QWidget* content = mw.ui->scrollArea->widget();
qDebug() << "main: content widget:" << content << "size"<<content->size();

return app.exec();

}
@

Everything else shows, but my custom widget isn't. Its onPaint() method is never called, and its size is (0,0) after mw.show():

size on construction: QSize(400, 600)
main: content widget: GenoEyeWidget(0x2542250) size QSize(0, 0)

[Chris Kawa]

Hi, welcome to devnet

As documentation states the policy set by setSizePolicy is not used when widget is placed in a layout (as is in your case). Because you place your widget in a scroll area before it is shown it probably gets resized to 0x0.

Try to change this
@
resize(page_w, page_h);
setSizePolicy(QSizePolicy::Fixed, QSizePolicy::Fixed);
@
to that
@
setFixedSize(page_w, page_h);
@