keeping a widget to be square

[jmsbc]

Hello,

I have a problem with placing a widget into a horizontalLayout and making it keep an equal aspect ratio (square).

Here is a rough outline of my code:

TargetDisplay::TargetDisplay(QWidget *parent)
    : QMainWindow(parent)
{
  ui.setupUi(this);
  d_plot = new RandomPlot(this);
 
  QSizePolicy policy(QSizePolicy::Preferred, QSizePolicy::Preferred);
  policy.setHeightForWidth(true);
  d_plot->setSizePolicy(policy);
 
  ui.horizontalLayout->insertWidget(0, d_plot);
}

TargetDisplay::TargetDisplay(QWidget *parent)
    : QMainWindow(parent)
{
  ui.setupUi(this);
  d_plot = new RandomPlot(this);

  QSizePolicy policy(QSizePolicy::Preferred, QSizePolicy::Preferred);
  policy.setHeightForWidth(true);
  d_plot->setSizePolicy(policy);

  ui.horizontalLayout->insertWidget(0, d_plot);
}

To copy to clipboard, switch view to plain text mode 

and then in my RandomPlot widget I have:

class RandomPlot: public QWidget
{
    Q_OBJECT
 
public:
  RandomPlot(QWidget *parent);
  ~RandomPlot();
 
  int heightForWidth(int w) const {
    return w;
  }
}

class RandomPlot: public QWidget
{
    Q_OBJECT

public:
  RandomPlot(QWidget *parent);
  ~RandomPlot();

  int heightForWidth(int w) const {
    return w;
  }
}

To copy to clipboard, switch view to plain text mode 

but my widget is not maintaining an equal aspect ratio. Can somebody please tell me what I'm doing wrong? Thank you!

-James

[wysota]

This will only work for a widget in a layout. For a top-level window you have to reimplement resizeEvent() and resize the widget to a proper aspect from within.

[jmsbc]

This will only work for a widget in a layout. For a top-level window you have to reimplement resizeEvent() and resize the widget to a proper aspect from within.

My widget is in HorizontalLayout:

ui.horizontalLayout->insertWidget(0, d_plot);

ui.horizontalLayout->insertWidget(0, d_plot);

To copy to clipboard, switch view to plain text mode 

Can somebody explain what I need to add to my original code? Thanks

[jmsbc]

Nevermind, I figured it out. Instead of adding d_plot directly to the horizontalLayout, I added it to QwtDynGridLayout first, and then added the layout to the horizontalLayout:

gLayout = new QwtDynGridLayout(this);
  gLayout->addWidget(d_plot);
  ui.horizontalLayout->insertLayout(0, gLayout);

gLayout = new QwtDynGridLayout(this);
  gLayout->addWidget(d_plot);
  ui.horizontalLayout->insertLayout(0, gLayout);

To copy to clipboard, switch view to plain text mode 

Now I get a square

[luf]

It's because the stretch factor on your horizontal layout when adding the widget is by default 0.

QHBoxLayout *hbox = new QHBoxLayout();
hbox->addWidget(mywidget, 1);

If you are using Qt Designer, set the layoutStretch parameters.

[luf]

As I found this layout manager that keeps a widgets square, I figured it would be wise to share it:
http://wiki.forum.nokia.com/index.ph...a_widget_in_Qt

Attached a zip file with source and example, in case it goes missing on the wiki.

Thanks to the heads at nokia for making this layout manager