- Qt 6.7
- Qt Quick Controls
- Customizing Qt Quick Controls
- Qt 6.7.2 Reference Documentation

# Customizing Qt Quick Controls

Qt Quick Controls consist of a hierarchy (tree) of items. In order to provide a custom look and feel, the default QML implementation of each item can be replaced with a custom one.

## Customizing a Control

Sometimes you'll want to create a "one-off" look for a specific part of your UI, and use a complete style everywhere else. Perhaps you're happy with the style you're using, but there's a certain button that has some special significance.

The first way to create this button is to simply define it in-place, wherever it is needed. For example, perhaps you're not satisfied with the Basic style's Button having square corners. To make them rounded, you can override the background item and set the radius property of Rectangle:

     import QtQuick
     import QtQuick.Controls

     ApplicationWindow {
         width: 400
         height: 400
         visible: true

         Button {
             id: button
             text: "A Special Button"
             background: Rectangle {
                 implicitWidth: 100
                 implicitHeight: 40
                 color: button.down ? "#d6d6d6" : "#f6f6f6"
                 border.color: "#26282a"
                 border.width: 1
                 radius: 4
             }
         }
     }

Note: as the different items that make up a control in any given style are designed to work together, it may be necessary to override other items to get the look you're after. In addition, not all styles can be customized. See the note in Customization Reference for more information.

The second way to create the button is good if you plan to use your rounded button in several places. It involves moving the code into its own QML file within your project.

For this approach, we'll copy the background code from the Basic style's `Button.qml`. This file can be found in the following path in your Qt installation:

`$QTDIR/qml/QtQuick/Controls/Basic/Button.qml`

After doing that, we'll simply add the following line:

     radius: 4

To avoid confusion with the controls in the module itself, we'll call the file `MyButton.qml`. To use the control in your application, refer to it by its filename:

     import QtQuick.Controls

     ApplicationWindow {
         MyButton {
             text: qsTr("A Special Button")
         }
     }

The third way to create the button is a bit more structured, both in terms of where the file sits in the file system and how it is used in QML. First, copy an existing file as you did above, but this time, put it into a subfolder in your project named (for example) `controls`. To use the control, first import the folder into a namespace:

     import QtQuick.Controls
     import "controls" as MyControls

     ApplicationWindow {
         MyControls.Button {
             text: qsTr("A Special Button")
         }
     }

As you now have the `MyControls` namespace, you can name the controls after their actual counterparts in the Qt Quick Controls module. You can repeat this process for any control that you wish to add.

An added benefit of these three methods is that it's not necessary to implement the template from scratch.

Note: the three approaches mentioned here do not work for customizing the attached ToolTip, as that is a shared item created internally. To do a one-off customization of a `ToolTip`, see Custom Tool Tips. To customize the attached `ToolTip`, it must be provided as part of your own style.

## Creating a Custom Style

There are several ways to go about creating your own styles. Below, we'll explain the various approaches.

### Definition of a Style

In Qt Quick Controls, a style is essentially a set of QML files within a single directory. There are four requirements for a style to be usable:

- At least one QML file whose name matches a control (for example, `Button.qml`) must exist.
- Each QML file must contain the relevant type from the QtQuick.Templates import as the root item. For example, Button.qml must contain a Button template as its root item.

  If we instead used the corresponding type from the QtQuick.Controls import as we did in the previous section, it would not work: the control we were defining would try to derive from itself.

- A qmldir file must exist alongside the QML file(s). Below is an example of a simple `qmldir` file for a style that provides a button:

       module MyStyle
       Button 2.15 Button.qml

  If you're using compile-time style selection, the qmldir should also import the fallback style:

       # ...
       import QtQuick.Controls.Basic auto

  This can also be done for run-time style selection instead of using, for example, QQuickStyle::setFallbackStyle().

  The directory structure for such a style looks like this:

       MyStyle
       ├─── Button.qml
       └─── qmldir

- The files must be in a directory that is findable via the QML Import Path.

  For example, if the path to MyStyle directory mentioned above was `/home/user/MyApp/MyStyle`, then `/home/user/MyApp` must be added to the QML import path.

  To use MyStyle in MyApp, refer to it by name:

  - `./MyApp -style MyStyle`

  The style name must match the casing of the style directory; passing mystyle or MYSTYLE is not supported.

By default, the styling system uses the Basic style as a fallback for controls that aren't implemented. To customize or extend any other built-in style, it is possible to specify a different fallback style using QQuickStyle.

What this means is that you can implement as many controls as you like for your custom style, and place them almost anywhere. It also allows users to create their own styles for your application.

#### Previewing Custom Styles in Qt Quick Designer

Using the approach above, it is possible to preview a custom style in Qt Quick Designer. In order to do so, ensure that the project has a qtquickcontrols2.conf file, and that the following entry exists:

     [Controls]
     Style=MyStyle

For more information, take a look at the Flat Style example.

### Style-specific C++ Extensions

Sometimes you may need to use C++ to extend your custom style.

- If the style that uses the type is the only style used by an application, register the type with the QML engine by adding the QML_ELEMENT macro and making the file part of your QML module:

  #### Using CMake

       qt_add_qml_module(ACoolItem
           URI MyItems
           VERSION 1.0
           SOURCES
               acoolcppitem.cpp acoolcppitem.h
       )

  #### Using QMake

       CONFIG += qmltypes
       QML_IMPORT_NAME = MyItems
       QML_IMPORT_MAJOR_VERSION = 1

  If the header the class is declared in is not accessible from your project's include path, you may have to amend the include path so that the generated registration code can be compiled.

       INCLUDEPATH += MyItems

  See Defining QML Types from C++ and Building a QML application for more information.

- If the style that uses the type is one of many styles used by an application, consider putting each style into a separate module. The modules will then be loaded on demand.

#### Considerations for custom styles

When implementing your own style and customizing controls, there are some points to keep in mind to ensure that your application is as performant as possible.

##### Avoid assigning an id to styles' implementations of item delegates

As explained in Definition of a Style, when you implement your own style for a control, you start off with the relevant template for that control. For example, a style's `Button.qml` will be structured similarly to this:

     T.Button {
         // ...

         background: Rectangle {
             // ...
         }

         contentItem: Text {
             // ...
         }

         // ...
     }

When you use a Button in your application, the `background` and `contentItem` items will be created and parented to the root `Button` item:

     // Creates the Button root item, the Rectangle background,
     // and the Text contentItem.
     Button {
         text: qsTr("Confirm")
     }

Suppose you then needed to do a one-off customization of the Button (as explained in Customizing a Control):

     import QtQuick
     import QtQuick.Controls

     ApplicationWindow {
         width: 400
         height: 400
         visible: true

         Button {
             id: button
             text: "A Special Button"
             background: Rectangle {
                 implicitWidth: 100
                 implicitHeight: 40
                 color: button.down ? "#d6d6d6" : "#f6f6f6"
                 border.color: "#26282a"
                 border.width: 1
                 radius: 4
             }
         }
     }

In QML, this would normally result in both the default `background` implementation and the one-off, custom `background` items being created. Qt Quick Controls uses a technique that avoids creating both items, and instead only creates the custom `background`, greatly improving the creation performance of controls.

This technique relies on the absence of an id in the style's implementation of that item. If an id is assigned, the technique cannot work, and both items will be created. For example, it can be tempting to assign an id to the `background` or `contentItem` so that other objects within the file can refer to those items:

     T.Button {
         // ...

         background: Rectangle {
             id: backgroundRect
             // ...
         }

         contentItem: Text {
             // Use backgroundRect in some way...
         }

         // ...
     }

With this code, every time a Button instance with a customized background is created, both backgrounds will be created, resulting in sub-optimal creation performance.

Prior to Qt 5.15, the old, unused background would be deleted to release the resources associated with it. However, as the control does not own the items, it should not delete them. As of Qt 5.15, old items are no longer deleted, and so the `backgroundRect` item will live longer than it needs to—typically until the application exits. Although the old item will be hidden, visually unparented from the control, and removed from the accessibility tree, it is important to keep the creation time and memory usage of these unused items in mind when assigning an id in this context.

##### Avoid imperative assignments of custom items

The technique mentioned in the section above only works when an item is declaratively assigned for the first time, and so imperative assignments will result in orphaned items. Always use declarative bindings to assign custom items when possible.

##### Don't import QtQuick.Controls in QML implementations

When writing the QML for your style's implementation of a control, it's important not to import `QtQuick.Controls`. Doing so will prevent the QML from being compiled by the QML compiler.

##### Implement types used by other types

Suppose you were using ScrollViews in your application, and decided that you want to customize their scroll bars. It is tempting to just implement a custom ScrollBar.qml and have ScrollView pick up the customized ScrollBar automatically. However, this will not work. You must implement both ScrollBar.qml and ScrollView.qml.

#### Attached properties

It is common for a style to have certain properties or attributes that apply to all controls. Attached properties are a great way of extending an item in QML without having to modify any existing C++ belonging to that item. For example, both the Material and Universal styles have an attached theme property that controls whether an item and its children will be rendered in a light or dark theme.

As an example, let's add an attached property that controls elevation. Our style will illustrate the elevation with a drop shadow; the higher the elevation, the larger the shadow.

The first step is to create a new Qt Quick Controls application in Qt Creator. After that, we add a C++ type that stores the elevation. Since the type will be used for every control supported by our style, and because we may wish to add other attached properties later on, we'll call it MyStyle. Here is `MyStyle.h`:

     #ifndef MYSTYLE_H
     #define MYSTYLE_H

     #include <QObject>
     #include <QtQml>

     class MyStyle : public QObject
     {
         Q_OBJECT
         Q_PROPERTY(int elevation READ elevation WRITE setElevation NOTIFY elevationChanged)

     public:
         explicit MyStyle(QObject *parent = nullptr);

         static MyStyle *qmlAttachedProperties(QObject *object);

         int elevation() const;
         void setElevation(int elevation);

     signals:
         void elevationChanged();

     private:
         int m_elevation;
     };

     QML_DECLARE_TYPEINFO(MyStyle, QML_HAS_ATTACHED_PROPERTIES)

     #endif // MYSTYLE_H

`MyStyle.cpp`:

     #include "mystyle.h"

     MyStyle::MyStyle(QObject *parent) :
         QObject(parent),
         m_elevation(0)
     {
     }

     MyStyle *MyStyle::qmlAttachedProperties(QObject *object)
     {
         return new MyStyle(object);
     }

     int MyStyle::elevation() const
     {
         return m_elevation;
     }

     void MyStyle::setElevation(int elevation)
     {
         if (elevation == m_elevation)
             return;

         m_elevation = elevation;
         emit elevationChanged();
     }

The `MyStyle` type is special in the sense that it shouldn't be instantiated, but rather used for its attached properties. For that reason, we register it in the following manner in `main.cpp`:

     #include <QGuiApplication>
     #include <QQmlApplicationEngine>

     #include "mystyle.h"

     int main(int argc, char *argv[])
     {
         QGuiApplication app(argc, argv);

         qmlRegisterUncreatableType<MyStyle>("MyStyle", 1, 0, "MyStyle", "MyStyle is an attached property");

         QQmlApplicationEngine engine;
         // Make the directory containing our style known to the QML engine.
         engine.addImportPath(":/");
         engine.load(QUrl(QLatin1String("qrc:/main.qml")));

         return app.exec();
     }

We then copy `Button.qml` from the Basic style in `$QTDIR/qml/QtQuick/Controls/Basic/` into a new `myproject` folder in our project directory. Add the newly copied `Button.qml` to `qml.qrc`, which is the resource file that contains our QML files.

Next, we add a drop shadow to the background delegate of the Button:

     // ...
     import QtQuick.Effects
     import MyStyle
     // ...

     background: Rectangle {
         // ...

         layer.enabled: control.enabled && control.MyStyle.elevation > 0
         layer.effect: MultiEffect {
             shadowEnabled: true
             shadowHorizontalOffset: 3
             shadowVerticalOffset: 3
             shadowColor: control.visualFocus ? "#330066ff" : "#aaaaaa"
             shadowBlur: control.pressed ? 0.8 : 0.4
         }
     }

Note that we:

- Don't bother using the drop shadow when the elevation is `0`
- Change the shadow's color depending on whether or not the button has focus
- Make the size of the shadow depend on the elevation

To try out the attached property, we create a Row with two Buttons in `main.qml`:

     import QtQuick
     import QtQuick.Controls

     import MyStyle 1.0

     ApplicationWindow {
         id: window
         width: 400
         height: 400
         visible: true

         Row {
             spacing: 20
             anchors.centerIn: parent

             Button {
                 text: "Button 1"
             }
             Button {
                 text: "Button 2"
                 MyStyle.elevation: 10
             }
         }
     }

One button has no elevation, and the other has an elevation of `10`.

With that in place, we can run our example. To tell the application to use our new style, we pass `-style MyStyle` as an application argument, but there are many ways to specify the style to use.

The end result:

Note that the `import MyStyle 1.0` statement is only necessary because we are using the attached property belonging to `MyStyle`. Both buttons will use our custom style, even if we were to remove the import.

## Customization Reference

The following snippets present examples where the Basic style's controls have been customized using the same approach as the Customizing a Control section. The code can be used as a starting point to implement a custom look and feel.

Note: The macOS and Windows styles are not suitable for customizing. It is instead recommended to always base a customized control on top of a single style that is available on all platforms, e.g Basic Style, Fusion Style, Imagine Style, Material Style, Universal Style. By doing so, you are guaranteed that it will always look the same, regardless of which style the application is run with. To learn how to use a different style, see Using Styles in Qt Quick Controls. Alternatively, you can create your own style.

### Customizing ApplicationWindow

ApplicationWindow consists of one visual item: background.

     import QtQuick
     import QtQuick.Controls.Basic

     ApplicationWindow {
         visible: true

         background: Rectangle {
             gradient: Gradient {
                 GradientStop { position: 0; color: "#ffffff" }
                 GradientStop { position: 1; color: "#c1bbf9" }
             }
         }
     }

### Customizing BusyIndicator

BusyIndicator consists of two visual items: background and contentItem.

     import QtQuick
     import QtQuick.Controls.Basic

     BusyIndicator {
         id: control

         contentItem: Item {
             implicitWidth: 64
             implicitHeight: 64

             Item {
                 id: item
                 x: parent.width / 2 - 32
                 y: parent.height / 2 - 32
                 width: 64
                 height: 64
                 opacity: control.running ? 1 : 0

                 Behavior on opacity {
                     OpacityAnimator {
                         duration: 250
                     }
                 }

                 RotationAnimator {
                     target: item
                     running: control.visible && control.running
                     from: 0
                     to: 360
                     loops: Animation.Infinite
                     duration: 1250
                 }

                 Repeater {
                     id: repeater
                     model: 6

                     Rectangle {
                         id: delegate
                         x: item.width / 2 - width / 2
                         y: item.height / 2 - height / 2
                         implicitWidth: 10
                         implicitHeight: 10
                         radius: 5
                         color: "#21be2b"

                         required property int index

                         transform: [
                             Translate {
                                 y: -Math.min(item.width, item.height) * 0.5 + 5
                             },
                             Rotation {
                                 angle: delegate.index / repeater.count * 360
                                 origin.x: 5
                                 origin.y: 5
                             }
                         ]
                     }
                 }
             }
         }
     }

### Customizing Button

Button consists of two visual items: background and content item.

     import QtQuick
     import QtQuick.Controls.Basic

     Button {
         id: control
         text: qsTr("Button")

         contentItem: Text {
             text: control.text
             font: control.font
             opacity: enabled ? 1.0 : 0.3
             color: control.down ? "#17a81a" : "#21be2b"
             horizontalAlignment: Text.AlignHCenter
             verticalAlignment: Text.AlignVCenter
             elide: Text.ElideRight
         }

         background: Rectangle {
             implicitWidth: 100
             implicitHeight: 40
             opacity: enabled ? 1 : 0.3
             border.color: control.down ? "#17a81a" : "#21be2b"
             border.width: 1
             radius: 2
         }
     }

### Customizing CheckBox

CheckBox consists of three visual items: background, contentItem and indicator.

     import QtQuick
     import QtQuick.Controls.Basic

     CheckBox {
         id: control
         text: qsTr("CheckBox")
         checked: true

         indicator: Rectangle {
             implicitWidth: 26
             implicitHeight: 26
             x: control.leftPadding
             y: parent.height / 2 - height / 2
             radius: 3
             border.color: control.down ? "#17a81a" : "#21be2b"

             Rectangle {
                 width: 14
                 height: 14
                 x: 6
                 y: 6
                 radius: 2
                 color: control.down ? "#17a81a" : "#21be2b"
                 visible: control.checked
             }
         }

         contentItem: Text {
             text: control.text
             font: control.font
             opacity: enabled ? 1.0 : 0.3
             color: control.down ? "#17a81a" : "#21be2b"
             verticalAlignment: Text.AlignVCenter
             leftPadding: control.indicator.width + control.spacing
         }
     }

### Customizing CheckDelegate

CheckDelegate consists of three visual items: background, contentItem and indicator.

     import QtQuick
     import QtQuick.Controls.Basic

     CheckDelegate {
         id: control
         text: qsTr("CheckDelegate")
         checked: true

         contentItem: Text {
             rightPadding: control.indicator.width + control.spacing
             text: control.text
             font: control.font
             opacity: enabled ? 1.0 : 0.3
             color: control.down ? "#17a81a" : "#21be2b"
             elide: Text.ElideRight
             verticalAlignment: Text.AlignVCenter
         }

         indicator: Rectangle {
             implicitWidth: 26
             implicitHeight: 26
             x: control.width - width - control.rightPadding
             y: control.topPadding + control.availableHeight / 2 - height / 2
             radius: 3
             color: "transparent"
             border.color: control.down ? "#17a81a" : "#21be2b"

             Rectangle {
                 width: 14
                 height: 14
                 x: 6
                 y: 6
                 radius: 2
                 color: control.down ? "#17a81a" : "#21be2b"
                 visible: control.checked
             }
         }

         background: Rectangle {
             implicitWidth: 100
             implicitHeight: 40
             visible: control.down || control.highlighted
             color: control.down ? "#bdbebf" : "#eeeeee"
         }
     }

### Customizing ComboBox

ComboBox consists of background, content item, popup, indicator, and delegate.

     pragma ComponentBehavior: Bound

     import QtQuick
     import QtQuick.Controls.Basic

     ComboBox {
         id: control
         model: ["First", "Second", "Third"]

         delegate: ItemDelegate {
             id: delegate

             required property var model
             required property int index

             width: control.width
             contentItem: Text {
                 text: delegate.model[control.textRole]
                 color: "#21be2b"
                 font: control.font
                 elide: Text.ElideRight
                 verticalAlignment: Text.AlignVCenter
             }
             highlighted: control.highlightedIndex === index
         }

         indicator: Canvas {
             id: canvas
             x: control.width - width - control.rightPadding
             y: control.topPadding + (control.availableHeight - height) / 2
             width: 12
             height: 8
             contextType: "2d"

             Connections {
                 target: control
                 function onPressedChanged() { canvas.requestPaint(); }
             }

             onPaint: {
                 context.reset();
                 context.moveTo(0, 0);
                 context.lineTo(width, 0);
                 context.lineTo(width / 2, height);
                 context.closePath();
                 context.fillStyle = control.pressed ? "#17a81a" : "#21be2b";
                 context.fill();
             }
         }

         contentItem: Text {
             leftPadding: 0
             rightPadding: control.indicator.width + control.spacing

             text: control.displayText
             font: control.font
             color: control.pressed ? "#17a81a" : "#21be2b"
             verticalAlignment: Text.AlignVCenter
             elide: Text.ElideRight
         }

         background: Rectangle {
             implicitWidth: 120
             implicitHeight: 40
             border.color: control.pressed ? "#17a81a" : "#21be2b"
             border.width: control.visualFocus ? 2 : 1
             radius: 2
         }

         popup: Popup {
             y: control.height - 1
             width: control.width
             implicitHeight: contentItem.implicitHeight
             padding: 1

             contentItem: ListView {
                 clip: true
                 implicitHeight: contentHeight
                 model: control.popup.visible ? control.delegateModel : null
                 currentIndex: control.highlightedIndex

                 ScrollIndicator.vertical: ScrollIndicator { }
             }

             background: Rectangle {
                 border.color: "#21be2b"
                 radius: 2
             }
         }
     }

As explained in ComboBox Model Roles, ComboBox supports multiple types of models.

Since all the models provide an anonymous property with `modelData`, the following expression retrieves the right text in all cases:

     text: model[control.textRole]

When you provide a specific `textRole` and a model with structured data that provides the selected role, this is expression is a regular property lookup. When you provide a model with singular data, such as a list of strings, and an empty `textRole`, this expression retrieves the `modelData`.

### Customizing DelayButton

DelayButton consists of two visual items: background and content item.

     import QtQuick
     import QtQuick.Controls.Basic

     DelayButton {
         id: control
         checked: true
         text: qsTr("Delay\nButton")

         contentItem: Text {
             text: control.text
             font: control.font
             opacity: enabled ? 1.0 : 0.3
             color: "white"
             horizontalAlignment: Text.AlignHCenter
             verticalAlignment: Text.AlignVCenter
             elide: Text.ElideRight
         }

         background: Rectangle {
             implicitWidth: 100
             implicitHeight: 100
             opacity: enabled ? 1 : 0.3
             color: control.down ? "#17a81a" : "#21be2b"
             radius: size / 2

             readonly property real size: Math.min(control.width, control.height)
             width: size
             height: size
             anchors.centerIn: parent

             Canvas {
                 id: canvas
                 anchors.fill: parent

                 Connections {
                     target: control
                     function onProgressChanged() { canvas.requestPaint(); }
                 }

                 onPaint: {
                     var ctx = getContext("2d")
                     ctx.clearRect(0, 0, width, height)
                     ctx.strokeStyle = "white"
                     ctx.lineWidth = parent.size / 20
                     ctx.beginPath()
                     var startAngle = Math.PI / 5 * 3
                     var endAngle = startAngle + control.progress * Math.PI / 5 * 9
                     ctx.arc(width / 2, height / 2, width / 2 - ctx.lineWidth / 2 - 2, startAngle, endAngle)
                     ctx.stroke()
                 }
             }
         }
     }

### Customizing Dial

Dial consists of two visual items: background and handle.

     import QtQuick
     import QtQuick.Controls.Basic

     Dial {
         id: control
         background: Rectangle {
             x: control.width / 2 - width / 2
             y: control.height / 2 - height / 2
             implicitWidth: 140
             implicitHeight: 140
             width: Math.max(64, Math.min(control.width, control.height))
             height: width
             color: "transparent"
             radius: width / 2
             border.color: control.pressed ? "#17a81a" : "#21be2b"
             opacity: control.enabled ? 1 : 0.3
         }

         handle: Rectangle {
             id: handleItem
             x: control.background.x + control.background.width / 2 - width / 2
             y: control.background.y + control.background.height / 2 - height / 2
             width: 16
             height: 16
             color: control.pressed ? "#17a81a" : "#21be2b"
             radius: 8
             antialiasing: true
             opacity: control.enabled ? 1 : 0.3
             transform: [
                 Translate {
                     y: -Math.min(control.background.width, control.background.height) * 0.4 + handleItem.height / 2
                 },
                 Rotation {
                     angle: control.angle
                     origin.x: handleItem.width / 2
                     origin.y: handleItem.height / 2
                 }
             ]
         }
     }

### Customizing Drawer

Drawer can have a visual background item.

     background: Rectangle {
         Rectangle {
             x: parent.width - 1
             width: 1
             height: parent.height
             color: "#21be2b"
         }
     }

### Customizing Frame

Frame consists of one visual item: background.

     import QtQuick
     import QtQuick.Controls.Basic

     Frame {
         background: Rectangle {
             color: "transparent"
             border.color: "#21be2b"
             radius: 2
         }

         Label {
             text: qsTr("Content goes here!")
         }
     }

### Customizing GroupBox

GroupBox consists of two visual items: background and label.

     import QtQuick
     import QtQuick.Controls.Basic

     GroupBox {
         id: control
         title: qsTr("GroupBox")

         background: Rectangle {
             y: control.topPadding - control.bottomPadding
             width: parent.width
             height: parent.height - control.topPadding + control.bottomPadding
             color: "transparent"
             border.color: "#21be2b"
             radius: 2
         }

         label: Label {
             x: control.leftPadding
             width: control.availableWidth
             text: control.title
             color: "#21be2b"
             elide: Text.ElideRight
         }

         Label {
             text: qsTr("Content goes here!")
         }
     }

### Customizing ItemDelegate

ItemDelegate consists of two visual items: background and content item.

     import QtQuick
     import QtQuick.Controls.Basic

     ItemDelegate {
         id: control
         text: qsTr("ItemDelegate")

         contentItem: Text {
             rightPadding: control.spacing
             text: control.text
             font: control.font
             color: control.enabled ? (control.down ? "#17a81a" : "#21be2b") : "#bdbebf"
             elide: Text.ElideRight
             verticalAlignment: Text.AlignVCenter
         }

         background: Rectangle {
             implicitWidth: 100
             implicitHeight: 40
             opacity: enabled ? 1 : 0.3
             color: control.down ? "#dddedf" : "#eeeeee"

             Rectangle {
                 width: parent.width
                 height: 1
                 color: control.down ? "#17a81a" : "#21be2b"
                 anchors.bottom: parent.bottom
             }
         }
     }

### Customizing Label

Label can have a visual background item.

     import QtQuick
     import QtQuick.Controls.Basic

     Label {
         text: qsTr("Label")
         color: "#21be2b"
     }

### Customizing Menu

- Menu consists of a visual background item.
- MenuItem consists of four visual items: background, content item, indicator, and arrow.
- MenuSeparator consists of a visual background and content item.

     import QtQuick
     import QtQuick.Controls.Basic

     Menu {
         id: menu

         Action { text: qsTr("Tool Bar"); checkable: true }
         Action { text: qsTr("Side Bar"); checkable: true; checked: true }
         Action { text: qsTr("Status Bar"); checkable: true; checked: true }

         MenuSeparator {
             contentItem: Rectangle {
                 implicitWidth: 200
                 implicitHeight: 1
                 color: "#21be2b"
             }
         }

         Menu {
             title: qsTr("Advanced")
             // ...
         }

         topPadding: 2
         bottomPadding: 2

         delegate: MenuItem {
             id: menuItem
             implicitWidth: 200
             implicitHeight: 40

             arrow: Canvas {
                 x: parent.width - width
                 implicitWidth: 40
                 implicitHeight: 40
                 visible: menuItem.subMenu
                 onPaint: {
                     var ctx = getContext("2d")
                     ctx.fillStyle = menuItem.highlighted ? "#ffffff" : "#21be2b"
                     ctx.moveTo(15, 15)
                     ctx.lineTo(width - 15, height / 2)
                     ctx.lineTo(15, height - 15)
                     ctx.closePath()
                     ctx.fill()
                 }
             }

             indicator: Item {
                 implicitWidth: 40
                 implicitHeight: 40
                 Rectangle {
                     width: 26
                     height: 26
                     anchors.centerIn: parent
                     visible: menuItem.checkable
                     border.color: "#21be2b"
                     radius: 3
                     Rectangle {
                         width: 14
                         height: 14
                         anchors.centerIn: parent
                         visible: menuItem.checked
                         color: "#21be2b"
                         radius: 2
                     }
                 }
             }

             contentItem: Text {
                 leftPadding: menuItem.indicator.width
                 rightPadding: menuItem.arrow.width
                 text: menuItem.text
                 font: menuItem.font
                 opacity: enabled ? 1.0 : 0.3
                 color: menuItem.highlighted ? "#ffffff" : "#21be2b"
                 horizontalAlignment: Text.AlignLeft
                 verticalAlignment: Text.AlignVCenter
                 elide: Text.ElideRight
             }

             background: Rectangle {
                 implicitWidth: 200
                 implicitHeight: 40
                 opacity: enabled ? 1 : 0.3
                 color: menuItem.highlighted ? "#21be2b" : "transparent"
             }
         }

         background: Rectangle {
             implicitWidth: 200
             implicitHeight: 40
             color: "#ffffff"
             border.color: "#21be2b"
             radius: 2
         }
     }

### Customizing MenuBar

MenuBar can have a visual background item, and MenuBarItem consists of two visual items: background and content item.

     import QtQuick
     import QtQuick.Controls.Basic

     MenuBar {
         id: menuBar

         Menu { title: qsTr("File") }
         Menu { title: qsTr("Edit") }
         Menu { title: qsTr("View") }
         Menu { title: qsTr("Help") }

         delegate: MenuBarItem {
             id: menuBarItem

             contentItem: Text {
                 text: menuBarItem.text
                 font: menuBarItem.font
                 opacity: enabled ? 1.0 : 0.3
                 color: menuBarItem.highlighted ? "#ffffff" : "#21be2b"
                 horizontalAlignment: Text.AlignLeft
                 verticalAlignment: Text.AlignVCenter
                 elide: Text.ElideRight
             }

             background: Rectangle {
                 implicitWidth: 40
                 implicitHeight: 40
                 opacity: enabled ? 1 : 0.3
                 color: menuBarItem.highlighted ? "#21be2b" : "transparent"
             }
         }

         background: Rectangle {
             implicitWidth: 40
             implicitHeight: 40
             color: "#ffffff"

             Rectangle {
                 color: "#21be2b"
                 width: parent.width
                 height: 1
                 anchors.bottom: parent.bottom
             }
         }
     }

### Customizing PageIndicator

PageIndicator consists of a background, content item, and delegate.

     import QtQuick
     import QtQuick.Controls.Basic

     PageIndicator {
         id: control
         count: 5
         currentIndex: 2

         delegate: Rectangle {
             implicitWidth: 8
             implicitHeight: 8

             radius: width / 2
             color: "#21be2b"

             opacity: index === control.currentIndex ? 0.95 : pressed ? 0.7 : 0.45

             required property int index

             Behavior on opacity {
                 OpacityAnimator {
                     duration: 100
                 }
             }
         }
     }

### Customizing Pane

Pane consists of a background.

     import QtQuick
     import QtQuick.Controls.Basic

     Pane {
         background: Rectangle {
             color: "#eeeeee"
         }

         Label {
             text: qsTr("Content goes here!")
         }
     }

### Customizing Popup

Popup consists of a background and content item.

     import QtQuick
     import QtQuick.Controls.Basic

     Popup {
         id: popup
         background: Rectangle {
             implicitWidth: 200
             implicitHeight: 200
             border.color: "#444"
         }
         contentItem: Column {}
     }

### Customizing ProgressBar

ProgressBar consists of two visual items: background and content item.

     import QtQuick
     import QtQuick.Controls.Basic

     ProgressBar {
         id: control
         value: 0.5
         padding: 2

         background: Rectangle {
             implicitWidth: 200
             implicitHeight: 6
             color: "#e6e6e6"
             radius: 3
         }

         contentItem: Item {
             implicitWidth: 200
             implicitHeight: 4

             // Progress indicator for determinate state.
             Rectangle {
                 width: control.visualPosition * parent.width
                 height: parent.height
                 radius: 2
                 color: "#17a81a"
                 visible: !control.indeterminate
             }

             // Scrolling animation for indeterminate state.
             Item {
                 anchors.fill: parent
                 visible: control.indeterminate
                 clip: true

                 Row {
                     spacing: 20

                     Repeater {
                         model: control.width / 40 + 1

                         Rectangle {
                             color: "#17a81a"
                             width: 20
                             height: control.height
                         }
                     }
                     XAnimator on x {
                         from: 0
                         to: -40
                         loops: Animation.Infinite
                         running: control.indeterminate
                     }
                 }
             }
         }
     }

Above, the content item is also animated to represent an indeterminate progress bar state.

### Customizing RadioButton

RadioButton consists of three visual items: background, content item and indicator.

     import QtQuick
     import QtQuick.Controls.Basic

     RadioButton {
         id: control
         text: qsTr("RadioButton")
         checked: true

         indicator: Rectangle {
             implicitWidth: 26
             implicitHeight: 26
             x: control.leftPadding
             y: parent.height / 2 - height / 2
             radius: 13
             border.color: control.down ? "#17a81a" : "#21be2b"

             Rectangle {
                 width: 14
                 height: 14
                 x: 6
                 y: 6
                 radius: 7
                 color: control.down ? "#17a81a" : "#21be2b"
                 visible: control.checked
             }
         }

         contentItem: Text {
             text: control.text
             font: control.font
             opacity: enabled ? 1.0 : 0.3
             color: control.down ? "#17a81a" : "#21be2b"
             verticalAlignment: Text.AlignVCenter
             leftPadding: control.indicator.width + control.spacing
         }
     }

### Customizing RadioDelegate

RadioDelegate consists of three visual items: background, contentItem and indicator.

     import QtQuick
     import QtQuick.Controls.Basic

     RadioDelegate {
         id: control
         text: qsTr("RadioDelegate")
         checked: true

         contentItem: Text {
             rightPadding: control.indicator.width + control.spacing
             text: control.text
             font: control.font
             opacity: enabled ? 1.0 : 0.3
             color: control.down ? "#17a81a" : "#21be2b"
             elide: Text.ElideRight
             verticalAlignment: Text.AlignVCenter
         }

         indicator: Rectangle {
             implicitWidth: 26
             implicitHeight: 26
             x: control.width - width - control.rightPadding
             y: parent.height / 2 - height / 2
             radius: 13
             color: "transparent"
             border.color: control.down ? "#17a81a" : "#21be2b"

             Rectangle {
                 width: 14
                 height: 14
                 x: 6
                 y: 6
                 radius: 7
                 color: control.down ? "#17a81a" : "#21be2b"
                 visible: control.checked
             }
         }

         background: Rectangle {
             implicitWidth: 100
             implicitHeight: 40
             visible: control.down || control.highlighted
             color: control.down ? "#bdbebf" : "#eeeeee"
         }
     }

### Customizing RangeSlider

RangeSlider consists of three visual items: background, first.handle and second.handle.

     import QtQuick
     import QtQuick.Controls.Basic

     RangeSlider {
         id: control
         first.value: 0.25
         second.value: 0.75

         background: Rectangle {
             x: control.leftPadding
             y: control.topPadding + control.availableHeight / 2 - height / 2
             implicitWidth: 200
             implicitHeight: 4
             width: control.availableWidth
             height: implicitHeight
             radius: 2
             color: "#bdbebf"

             Rectangle {
                 x: control.first.visualPosition * parent.width
                 width: control.second.visualPosition * parent.width - x
                 height: parent.height
                 color: "#21be2b"
                 radius: 2
             }
         }

         first.handle: Rectangle {
             x: control.leftPadding + control.first.visualPosition * (control.availableWidth - width)
             y: control.topPadding + control.availableHeight / 2 - height / 2
             implicitWidth: 26
             implicitHeight: 26
             radius: 13
             color: control.first.pressed ? "#f0f0f0" : "#f6f6f6"
             border.color: "#bdbebf"
         }

         second.handle: Rectangle {
             x: control.leftPadding + control.second.visualPosition * (control.availableWidth - width)
             y: control.topPadding + control.availableHeight / 2 - height / 2
             implicitWidth: 26
             implicitHeight: 26
             radius: 13
             color: control.second.pressed ? "#f0f0f0" : "#f6f6f6"
             border.color: "#bdbebf"
         }
     }

### Customizing RoundButton

RoundButton can be customized in the same manner as Button.

### Customizing ScrollBar

ScrollBar consists of two visual items: background and content item.

     import QtQuick
     import QtQuick.Controls.Basic

     ScrollBar {
         id: control
         size: 0.3
         position: 0.2
         active: true
         orientation: Qt.Vertical

         contentItem: Rectangle {
             implicitWidth: 6
             implicitHeight: 100
             radius: width / 2
             color: control.pressed ? "#81e889" : "#c2f4c6"
             // Hide the ScrollBar when it's not needed.
             opacity: control.policy === ScrollBar.AlwaysOn || (control.active && control.size < 1.0) ? 0.75 : 0

             // Animate the changes in opacity (default duration is 250 ms).
             Behavior on opacity {
                 NumberAnimation {}
             }
         }
     }

### Customizing ScrollIndicator

ScrollIndicator consists of two visual items: background and content item.

     import QtQuick
     import QtQuick.Controls.Basic

     ScrollIndicator {
         id: control
         size: 0.3
         position: 0.2
         active: true
         orientation: Qt.Vertical

         contentItem: Rectangle {
             implicitWidth: 2
             implicitHeight: 100
             color: "#c2f4c6"
         }
     }

### Customizing ScrollView

ScrollView consists of a background item, and horizontal and vertical scroll bars.

     ScrollView {
         id: control

         width: 200
         height: 200
         focus: true

         Label {
             text: "ABC"
             font.pixelSize: 224
         }

         ScrollBar.vertical: ScrollBar {
             parent: control
             x: control.mirrored ? 0 : control.width - width
             y: control.topPadding
             height: control.availableHeight
             active: control.ScrollBar.horizontal.active
         }

         ScrollBar.horizontal: ScrollBar {
             parent: control
             x: control.leftPadding
             y: control.height - height
             width: control.availableWidth
             active: control.ScrollBar.vertical.active
         }

         background: Rectangle {
             border.color: control.activeFocus ? "#21be2b" : "#bdbebf"
         }
     }

### Customizing Slider

Slider consists of two visual items: background, and handle.

     import QtQuick
     import QtQuick.Controls.Basic

     Slider {
         id: control
         value: 0.5

         background: Rectangle {
             x: control.leftPadding
             y: control.topPadding + control.availableHeight / 2 - height / 2
             implicitWidth: 200
             implicitHeight: 4
             width: control.availableWidth
             height: implicitHeight
             radius: 2
             color: "#bdbebf"

             Rectangle {
                 width: control.visualPosition * parent.width
                 height: parent.height
                 color: "#21be2b"
                 radius: 2
             }
         }

         handle: Rectangle {
             x: control.leftPadding + control.visualPosition * (control.availableWidth - width)
             y: control.topPadding + control.availableHeight / 2 - height / 2
             implicitWidth: 26
             implicitHeight: 26
             radius: 13
             color: control.pressed ? "#f0f0f0" : "#f6f6f6"
             border.color: "#bdbebf"
         }
     }

### Customizing SpinBox

SpinBox consists of four visual items: background, contentItem, up indicator, and down indicator.

     import QtQuick
     import QtQuick.Controls.Basic

     SpinBox {
         id: control
         value: 50
         editable: true

         contentItem: TextInput {
             z: 2
             text: control.textFromValue(control.value, control.locale)

             font: control.font
             color: "#21be2b"
             selectionColor: "#21be2b"
             selectedTextColor: "#ffffff"
             horizontalAlignment: Qt.AlignHCenter
             verticalAlignment: Qt.AlignVCenter

             readOnly: !control.editable
             validator: control.validator
             inputMethodHints: Qt.ImhFormattedNumbersOnly
         }

         up.indicator: Rectangle {
             x: control.mirrored ? 0 : parent.width - width
             height: parent.height
             implicitWidth: 40
             implicitHeight: 40
             color: control.up.pressed ? "#e4e4e4" : "#f6f6f6"
             border.color: enabled ? "#21be2b" : "#bdbebf"

             Text {
                 text: "+"
                 font.pixelSize: control.font.pixelSize * 2
                 color: "#21be2b"
                 anchors.fill: parent
                 fontSizeMode: Text.Fit
                 horizontalAlignment: Text.AlignHCenter
                 verticalAlignment: Text.AlignVCenter
             }
         }

         down.indicator: Rectangle {
             x: control.mirrored ? parent.width - width : 0
             height: parent.height
             implicitWidth: 40
             implicitHeight: 40
             color: control.down.pressed ? "#e4e4e4" : "#f6f6f6"
             border.color: enabled ? "#21be2b" : "#bdbebf"

             Text {
                 text: "-"
                 font.pixelSize: control.font.pixelSize * 2
                 color: "#21be2b"
                 anchors.fill: parent
                 fontSizeMode: Text.Fit
                 horizontalAlignment: Text.AlignHCenter
                 verticalAlignment: Text.AlignVCenter
             }
         }

         background: Rectangle {
             implicitWidth: 140
             border.color: "#bdbebf"
         }
     }

### Customizing SplitView

SplitView consists of a visual handle delegate.

     SplitView {
         id: splitView
         anchors.fill: parent

         handle: Rectangle {
             implicitWidth: 4
             implicitHeight: 4
             color: SplitHandle.pressed ? "#81e889"
                 : (SplitHandle.hovered ? Qt.lighter("#c2f4c6", 1.1) : "#c2f4c6")
         }

         Rectangle {
             implicitWidth: 150
             color: "#444"
         }
         Rectangle {
             implicitWidth: 50
             color: "#666"
         }
     }

### Customizing StackView

StackView can have a visual background item, and it allows customizing the transitions that are used for push, pop, and replace operations.

     import QtQuick
     import QtQuick.Controls.Basic

     StackView {
         id: control

         popEnter: Transition {
             XAnimator {
                 from: (control.mirrored ? -1 : 1) * -control.width
                 to: 0
                 duration: 400
                 easing.type: Easing.OutCubic
             }
         }

         popExit: Transition {
             XAnimator {
                 from: 0
                 to: (control.mirrored ? -1 : 1) * control.width
                 duration: 400
                 easing.type: Easing.OutCubic
             }
         }
     }

### Customizing SwipeDelegate

SwipeDelegate consists of six visual items: background, content item, indicator, `swipe.left`, `swipe.right`, and `swipe.behind`.

     import QtQuick
     import QtQuick.Controls.Basic

     SwipeDelegate {
         id: control
         text: qsTr("SwipeDelegate")

         Component {
             id: component

             Rectangle {
                 color: SwipeDelegate.pressed ? "#333" : "#444"
                 width: parent.width
                 height: parent.height
                 clip: true

                 Label {
                     text: qsTr("Press me!")
                     color: "#21be2b"
                     anchors.centerIn: parent
                 }
             }
         }

         swipe.left: component
         swipe.right: component

         contentItem: Text {
             text: control.text
             font: control.font
             color: control.enabled ? (control.down ? "#17a81a" : "#21be2b") : "#bdbebf"
             elide: Text.ElideRight
             verticalAlignment: Text.AlignVCenter

             Behavior on x {
                 enabled: !control.down
                 NumberAnimation {
                     easing.type: Easing.InOutCubic
                     duration: 400
                 }
             }
         }
     }

### Customizing SwipeView

SwipeView can have a visual background item. The navigation is implemented by the content item.

     import QtQuick
     import QtQuick.Controls.Basic

     SwipeView {
         id: control

         background: Rectangle {
             color: "#eeeeee"
         }
     }

### Customizing Switch

Switch consists of three visual items: background, content item and indicator.

     import QtQuick
     import QtQuick.Controls.Basic

     Switch {
         id: control
         text: qsTr("Switch")

         indicator: Rectangle {
             implicitWidth: 48
             implicitHeight: 26
             x: control.leftPadding
             y: parent.height / 2 - height / 2
             radius: 13
             color: control.checked ? "#17a81a" : "#ffffff"
             border.color: control.checked ? "#17a81a" : "#cccccc"

             Rectangle {
                 x: control.checked ? parent.width - width : 0
                 width: 26
                 height: 26
                 radius: 13
                 color: control.down ? "#cccccc" : "#ffffff"
                 border.color: control.checked ? (control.down ? "#17a81a" : "#21be2b") : "#999999"
             }
         }

         contentItem: Text {
             text: control.text
             font: control.font
             opacity: enabled ? 1.0 : 0.3
             color: control.down ? "#17a81a" : "#21be2b"
             verticalAlignment: Text.AlignVCenter
             leftPadding: control.indicator.width + control.spacing
         }
     }

### Customizing SwitchDelegate

SwitchDelegate consists of three visual items: background, contentItem and indicator.

     import QtQuick
     import QtQuick.Controls.Basic

     SwitchDelegate {
         id: control
         text: qsTr("SwitchDelegate")
         checked: true

         contentItem: Text {
             rightPadding: control.indicator.width + control.spacing
             text: control.text
             font: control.font
             opacity: enabled ? 1.0 : 0.3
             color: control.down ? "#17a81a" : "#21be2b"
             elide: Text.ElideRight
             verticalAlignment: Text.AlignVCenter
         }

         indicator: Rectangle {
             implicitWidth: 48
             implicitHeight: 26
             x: control.width - width - control.rightPadding
             y: parent.height / 2 - height / 2
             radius: 13
             color: control.checked ? "#17a81a" : "transparent"
             border.color: control.checked ? "#17a81a" : "#cccccc"

             Rectangle {
                 x: control.checked ? parent.width - width : 0
                 width: 26
                 height: 26
                 radius: 13
                 color: control.down ? "#cccccc" : "#ffffff"
                 border.color: control.checked ? (control.down ? "#17a81a" : "#21be2b") : "#999999"
             }
         }

         background: Rectangle {
             implicitWidth: 100
             implicitHeight: 40
             visible: control.down || control.highlighted
             color: control.down ? "#bdbebf" : "#eeeeee"
         }
     }

### Customizing TabBar

TabBar consists of two visual items: background, and contentItem.

     import QtQuick
     import QtQuick.Controls.Basic

     TabBar {
         id: control

         background: Rectangle {
             color: "#eeeeee"
         }

         TabButton {
             text: qsTr("Home")
         }
         TabButton {
             text: qsTr("Discover")
         }
         TabButton {
             text: qsTr("Activity")
         }
     }

### Customizing TabButton

TabButton can be customized in the same manner as Button.

### Customizing TextArea

TextArea consists of a background item.

     import QtQuick
     import QtQuick.Controls.Basic

     TextArea {
         id: control
         placeholderText: qsTr("Enter description")

         background: Rectangle {
             implicitWidth: 200
             implicitHeight: 40
             border.color: control.enabled ? "#21be2b" : "transparent"
         }
     }

### Customizing TextField

TextField consists of a background item.

     import QtQuick
     import QtQuick.Controls.Basic

     TextField {
         id: control
         placeholderText: qsTr("Enter description")

         background: Rectangle {
             implicitWidth: 200
             implicitHeight: 40
             color: control.enabled ? "transparent" : "#353637"
             border.color: control.enabled ? "#21be2b" : "transparent"
         }
     }

### Customizing ToolBar

ToolBar consists of one visual item: background.

     ToolBar {
         id: control

         background: Rectangle {
             implicitHeight: 40
             color: "#eeeeee"

             Rectangle {
                 width: parent.width
                 height: 1
                 anchors.bottom: parent.bottom
                 color: "transparent"
                 border.color: "#21be2b"
             }
         }

         RowLayout {
             anchors.fill: parent
             ToolButton {
                 text: qsTr("Undo")
             }
             ToolButton {
                 text: qsTr("Redo")
             }
         }
     }

### Customizing ToolButton

ToolButton consists of two visual items: background and content item.

     import QtQuick
     import QtQuick.Controls.Basic

     ToolButton {
         id: control
         text: qsTr("ToolButton")
         width: 120

         contentItem: Text {
             text: control.text
             font: control.font
             opacity: enabled ? 1.0 : 0.3
             color: control.down ? "#17a81a" : "#21be2b"
             horizontalAlignment: Text.AlignHCenter
             verticalAlignment: Text.AlignVCenter
             elide: Text.ElideRight
         }

         background: Rectangle {
             implicitWidth: 40
             implicitHeight: 40
             color: Qt.darker("#33333333", control.enabled && (control.checked || control.highlighted) ? 1.5 : 1.0)
             opacity: enabled ? 1 : 0.3
             visible: control.down || (control.enabled && (control.checked || control.highlighted))
         }
     }

### Customizing ToolSeparator

ToolSeparator consists of two visual items: background and content item.

     ToolBar {
         RowLayout {
             anchors.fill: parent

             ToolButton {
                 text: qsTr("Action 1")
             }
             ToolButton {
                 text: qsTr("Action 2")
             }

             ToolSeparator {
                 padding: vertical ? 10 : 2
                 topPadding: vertical ? 2 : 10
                 bottomPadding: vertical ? 2 : 10

                 contentItem: Rectangle {
                     implicitWidth: parent.vertical ? 1 : 24
                     implicitHeight: parent.vertical ? 24 : 1
                     color: "#c3c3c3"
                 }
             }

             ToolButton {
                 text: qsTr("Action 3")
             }
             ToolButton {
                 text: qsTr("Action 4")
             }

             Item {
                 Layout.fillWidth: true
             }
         }
     }

### Customizing ToolTip

ToolTip consists of two visual items: background and content item.

     import QtQuick
     import QtQuick.Controls.Basic

     ToolTip {
         id: control
         text: qsTr("A descriptive tool tip of what the button does")

         contentItem: Text {
             text: control.text
             font: control.font
             color: "#21be2b"
         }

         background: Rectangle {
             border.color: "#21be2b"
         }
     }

Note: to customize the attached ToolTip, it must be provided as part of your own style. To do a one-off customization of a `ToolTip`, see Custom Tool Tips.

### Customizing Tumbler

Tumbler consists of three visual items: background, contentItem, and delegate.

     import QtQuick
     import QtQuick.Controls.Basic

     Tumbler {
         id: control
         model: 15

         background: Item {
             Rectangle {
                 opacity: control.enabled ? 0.2 : 0.1
                 border.color: "#000000"
                 width: parent.width
                 height: 1
                 anchors.top: parent.top
             }

             Rectangle {
                 opacity: control.enabled ? 0.2 : 0.1
                 border.color: "#000000"
                 width: parent.width
                 height: 1
                 anchors.bottom: parent.bottom
             }
         }

         delegate: Text {
             text: qsTr("Item %1").arg(modelData + 1)
             font: control.font
             horizontalAlignment: Text.AlignHCenter
             verticalAlignment: Text.AlignVCenter
             opacity: 1.0 - Math.abs(Tumbler.displacement) / (control.visibleItemCount / 2)

             required property var modelData
             required property int index
         }

         Rectangle {
             anchors.horizontalCenter: control.horizontalCenter
             y: control.height * 0.4
             width: 40
             height: 1
             color: "#21be2b"
         }

         Rectangle {
             anchors.horizontalCenter: control.horizontalCenter
             y: control.height * 0.6
             width: 40
             height: 1
             color: "#21be2b"
         }
     }

If you want to define your own contentItem, use either a ListView or PathView as the root item. For a wrapping Tumbler, use PathView:

     Tumbler {
         id: tumbler

         contentItem: PathView {
             id: pathView
             model: tumbler.model
             delegate: tumbler.delegate
             clip: true
             pathItemCount: tumbler.visibleItemCount + 1
             preferredHighlightBegin: 0.5
             preferredHighlightEnd: 0.5
             dragMargin: width / 2

             path: Path {
                 startX: pathView.width / 2
                 startY: -pathView.delegateHeight / 2
                 PathLine {
                     x: pathView.width / 2
                     y: pathView.pathItemCount * pathView.delegateHeight - pathView.delegateHeight / 2
                 }
             }

             property real delegateHeight: tumbler.availableHeight / tumbler.visibleItemCount
         }
     }

For a non-wrapping Tumbler, use ListView:

     Tumbler {
         id: tumbler

         contentItem: ListView {
             model: tumbler.model
             delegate: tumbler.delegate

             snapMode: ListView.SnapToItem
             highlightRangeMode: ListView.StrictlyEnforceRange
             preferredHighlightBegin: height / 2 - (height / tumbler.visibleItemCount / 2)
             preferredHighlightEnd: height / 2 + (height / tumbler.visibleItemCount / 2)
             clip: true
         }
     }