- Qt 6.9
- Qt Widgets
- C++ Classes
- QRubberBand
- Qt 6.9.2 Reference Documentation

# QRubberBand Class

The QRubberBand class provides a rectangle or line that can indicate a selection or a boundary. More...

Header: | `#include <QRubberBand>`
CMake: | `find_package(Qt6 REQUIRED COMPONENTS Widgets)` `target_link_libraries(mytarget PRIVATE Qt6::Widgets)`
qmake: | `QT += widgets`
Inherits: | QWidget

- List of all members, including inherited members

## Public Types

enum | Shape { Line, Rectangle }

## Public Functions

| QRubberBand(QRubberBand::Shape s, QWidget *p = nullptr)
virtual | ~QRubberBand()
QRubberBand::Shape | shape() const

## Protected Functions

virtual void | initStyleOption(QStyleOptionRubberBand *option) const

## Reimplemented Protected Functions

virtual void | changeEvent(QEvent *e) override
virtual bool | event(QEvent *e) override
virtual void | moveEvent(QMoveEvent *) override
virtual void | paintEvent(QPaintEvent *) override
virtual void | resizeEvent(QResizeEvent *) override
virtual void | showEvent(QShowEvent *e) override

## Detailed Description

A rubber band is often used to show a new bounding area (as in a QSplitter or a QDockWidget that is undocking). Historically this has been implemented using a QPainter and XOR, but this approach doesn't always work properly since rendering can happen in the window below the rubber band, but before the rubber band has been "erased".

You can create a QRubberBand whenever you need to render a rubber band around a given area (or to represent a single line), then call setGeometry(), move() or resize() to position and size it. A common pattern is to do this in conjunction with mouse events. For example:

     void Widget::mousePressEvent(QMouseEvent *event)
     {
         origin = event->pos();
         if (!rubberBand)
             rubberBand = new QRubberBand(QRubberBand::Rectangle, this);
         rubberBand->setGeometry(QRect(origin, QSize()));
         rubberBand->show();
     }

     void Widget::mouseMoveEvent(QMouseEvent *event)
     {
         rubberBand->setGeometry(QRect(origin, event->pos()).normalized());
     }

     void Widget::mouseReleaseEvent(QMouseEvent *event)
     {
         rubberBand->hide();
         // determine selection, for example using QRect::intersects()
         // and QRect::contains().
     }

If you pass a parent to QRubberBand's constructor, the rubber band will display only inside its parent, but stays on top of other child widgets. If no parent is passed, QRubberBand will act as a top-level widget.

Call show() to make the rubber band visible; also when the rubber band is not a top-level. Hiding or destroying the widget will make the rubber band disappear. The rubber band can be a Rectangle or a Line (vertical or horizontal), depending on the shape() it was given when constructed.

## Member Type Documentation

### enum QRubberBand::Shape

This enum specifies what shape a QRubberBand should have. This is a drawing hint that is passed down to the style system, and can be interpreted by each QStyle.

Constant | Value | Description
--- | --- | ---
`QRubberBand::Line` | `0` | A QRubberBand can represent a vertical or horizontal line. Geometry is still given in rect() and the line will fill the given geometry on most styles.
`QRubberBand::Rectangle` | `1` | A QRubberBand can represent a rectangle. Some styles will interpret this as a filled (often semi-transparent) rectangle, or a rectangular outline.

## Member Function Documentation

### `[explicit]` QRubberBand::QRubberBand(QRubberBand::Shape s, QWidget *p = nullptr)

Constructs a rubber band of shape s, with parent p.

By default a rectangular rubber band (s is `Rectangle`) will use a mask, so that a small border of the rectangle is all that is visible. Some styles (e.g., native macOS) will change this and call QWidget::setWindowOpacity() to make a semi-transparent filled selection rectangle.

### `[virtual noexcept]` QRubberBand::~QRubberBand()

Destructor.

### `[override virtual protected]` void QRubberBand::changeEvent(QEvent *e)

Reimplements: QWidget::changeEvent(QEvent *event).

### `[override virtual protected]` bool QRubberBand::event(QEvent *e)

Reimplements: QWidget::event(QEvent *event).

### `[virtual protected]` void QRubberBand::initStyleOption(QStyleOptionRubberBand *option) const

Initialize option with the values from this QRubberBand. This method is useful for subclasses when they need a QStyleOptionRubberBand, but don't want to fill in all the information themselves.

See also QStyleOption::initFrom().

### `[override virtual protected]` void QRubberBand::moveEvent(QMoveEvent *)

Reimplements: QWidget::moveEvent(QMoveEvent *event).

### `[override virtual protected]` void QRubberBand::paintEvent(QPaintEvent *)

Reimplements: QWidget::paintEvent(QPaintEvent *event).

### `[override virtual protected]` void QRubberBand::resizeEvent(QResizeEvent *)

Reimplements: QWidget::resizeEvent(QResizeEvent *event).

### QRubberBand::Shape QRubberBand::shape() const

Returns the shape of this rubber band. The shape can only be set upon construction.

### `[override virtual protected]` void QRubberBand::showEvent(QShowEvent *e)

Reimplements: QWidget::showEvent(QShowEvent *event).