- Qt 5.15
- Qt Widgets
- Dynamic Layouts Example
- Qt 5.15.19 Reference Documentation

# Dynamic Layouts Example

Shows how to re-orient widgets in running applications.

Dynamic Layouts implements dynamically placed widgets within running applications. The widget placement depends on whether `Horizontal` or `Vertical` is chosen.

For more information, visit the Layout Management page.

#### Dialog Constructor

To begin with, the application creates the UI components by calling the following methods:

- createRotatableGroupBox()
- createOptionsGroupBox()
- createButtonBox()

It then adds the UI components to a GridLayout (`mainLayout`).

Finally, `Dialog::rotateWidgets()` is called.

         createOptionsGroupBox();
         createButtonBox();

         mainLayout = new QGridLayout;
         mainLayout->addWidget(rotatableGroupBox, 0, 0);
         mainLayout->addWidget(optionsGroupBox, 1, 0);
         mainLayout->addWidget(buttonBox, 2, 0);
         setLayout(mainLayout);

         mainLayout->setSizeConstraint(QLayout::SetMinimumSize);

         setWindowTitle(tr("Dynamic Layouts"));

#### Creating the Main Widgets

The `createRotatableGroupBox()` method creates a rotatable group box, then adds a series of widgets:

- QSpinBox
- QSlider
- QDial
- QProgressBar

It goes on to add signals and slots to each widget, and assigns a QGridLayout called rotatableLayout.

     void Dialog::createRotatableGroupBox()
     {
         rotatableGroupBox = new QGroupBox(tr("Rotatable Widgets"));

         rotatableWidgets.enqueue(new QSpinBox);
         rotatableWidgets.enqueue(new QSlider);
         rotatableWidgets.enqueue(new QDial);
         rotatableWidgets.enqueue(new QProgressBar);

         int n = rotatableWidgets.count();
         for (int i = 0; i < n; ++i) {
             connect(rotatableWidgets[i], SIGNAL(valueChanged(int)),
                     rotatableWidgets[(i + 1) % n], SLOT(setValue(int)));
         }

         rotatableLayout = new QGridLayout;
         rotatableGroupBox->setLayout(rotatableLayout);

         rotateWidgets();
     }

#### Adding Options

`createOptionsGroupBox()` creates the following widgets:

- `optionsGroupBox`
- `buttonsOrientationLabel`
- `buttonsOrientationComboBox`. The orientation of the ComboBox is either `horizontal` (default value) or `vertical`. These two values are added during the startup of the application. It is not possible to leave the option empty.

     void Dialog::createOptionsGroupBox()
     {
         optionsGroupBox = new QGroupBox(tr("Options"));

         buttonsOrientationLabel = new QLabel(tr("Orientation of buttons:"));

         buttonsOrientationComboBox = new QComboBox;
         buttonsOrientationComboBox->addItem(tr("Horizontal"), Qt::Horizontal);
         buttonsOrientationComboBox->addItem(tr("Vertical"), Qt::Vertical);

         connect(buttonsOrientationComboBox,
                 QOverload<int>::of(&QComboBox::currentIndexChanged),
                 this,
                 &Dialog::buttonsOrientationChanged);

         optionsLayout = new QGridLayout;
         optionsLayout->addWidget(buttonsOrientationLabel, 0, 0);
         optionsLayout->addWidget(buttonsOrientationComboBox, 0, 1);
         optionsLayout->setColumnStretch(2, 1);
         optionsGroupBox->setLayout(optionsLayout);
     }

#### Adding Buttons

createButtonBox() constructs a QDialogButtonBox called `buttonBox` to which are added a `closeButton`, a `helpButton` and a `rotateWidgetsButton`. It then assigns a signal and a slot to each button in `buttonBox`.

     void Dialog::createButtonBox()
     {
         buttonBox = new QDialogButtonBox;

         closeButton = buttonBox->addButton(QDialogButtonBox::Close);
         helpButton = buttonBox->addButton(QDialogButtonBox::Help);
         rotateWidgetsButton = buttonBox->addButton(tr("Rotate &Widgets"),
                                                    QDialogButtonBox::ActionRole);

         connect(rotateWidgetsButton, &QPushButton::clicked, this, &Dialog::rotateWidgets);
         connect(closeButton, &QPushButton::clicked, this, &Dialog::close);
         connect(helpButton, &QPushButton::clicked, this, &Dialog::help);
     }

#### Rotating the Widgets

Removes the current widgets and activates the next widget.

     void Dialog::rotateWidgets()
     {
         Q_ASSERT(rotatableWidgets.count() % 2 == 0);

         for (QWidget *widget : qAsConst(rotatableWidgets))
             rotatableLayout->removeWidget(widget);

         rotatableWidgets.enqueue(rotatableWidgets.dequeue());

         const int n = rotatableWidgets.count();
         for (int i = 0; i < n / 2; ++i) {
             rotatableLayout->addWidget(rotatableWidgets[n - i - 1], 0, i);
             rotatableLayout->addWidget(rotatableWidgets[i], 1, i);
         }
     }

#### Running the Example

To run the example from Qt Creator, open the Welcome mode and select the example from Examples. For more information, visit Building and Running an Example.

Example project @ code.qt.io