WheelHandler

#include <wheelhandler.h>

Inheritance diagram for WheelHandler:

[legend]

Properties
bool	blockTargetWheel

bool	filterMouseEvents

qreal	horizontalStepSize

bool	keyNavigationEnabled

Qt::KeyboardModifiers	pageScrollModifiers

bool	scrollFlickableTarget

QML_ELEMENTQQuickItem *	target

qreal	verticalStepSize

Properties inherited from QObject
	objectName

Signals
void	blockTargetWheelChanged ()

void	filterMouseEventsChanged ()

void	horizontalStepSizeChanged ()

void	keyNavigationEnabledChanged ()

void	pageScrollModifiersChanged ()

void	scrollFlickableTargetChanged ()

void	targetChanged ()

void	verticalStepSizeChanged ()

void	wheel (KirigamiWheelEvent *wheel)

Public Member Functions
	WheelHandler (QObject *parent=nullptr)

bool	filterMouseEvents () const

qreal	horizontalStepSize () const

bool	keyNavigationEnabled () const

Qt::KeyboardModifiers	pageScrollModifiers () const

void	resetHorizontalStepSize ()

void	resetPageScrollModifiers ()

void	resetVerticalStepSize ()

Q_INVOKABLE bool	scrollDown (qreal stepSize=-1)

Q_INVOKABLE bool	scrollLeft (qreal stepSize=-1)

Q_INVOKABLE bool	scrollRight (qreal stepSize=-1)

Q_INVOKABLE bool	scrollUp (qreal stepSize=-1)

void	setFilterMouseEvents (bool enabled)

void	setHorizontalStepSize (qreal stepSize)

void	setKeyNavigationEnabled (bool enabled)

void	setPageScrollModifiers (Qt::KeyboardModifiers modifiers)

void	setTarget (QQuickItem *target)

void	setVerticalStepSize (qreal stepSize)

QQuickItem *	target () const

qreal	verticalStepSize () const

Public Member Functions inherited from QObject
	QObject (QObject *parent)

QBindable< QString >	bindableObjectName ()

bool	blockSignals (bool block)

const QObjectList &	children () const const

QMetaObject::Connection	connect (const QObject sender, const char signal, const char *method, Qt::ConnectionType type) const const

void	deleteLater ()

void	destroyed (QObject *obj)

bool	disconnect (const char signal, const QObject receiver, const char *method) const const

bool	disconnect (const QObject receiver, const char method) const const

void	dumpObjectInfo () const const

void	dumpObjectTree () const const

QList< QByteArray >	dynamicPropertyNames () const const

virtual bool	event (QEvent *e)

T	findChild (const QString &name, Qt::FindChildOptions options) const const

QList< T >	findChildren (const QRegularExpression &re, Qt::FindChildOptions options) const const

QList< T >	findChildren (const QString &name, Qt::FindChildOptions options) const const

QList< T >	findChildren (Qt::FindChildOptions options) const const

bool	inherits (const char *className) const const

void	installEventFilter (QObject *filterObj)

bool	isQuickItemType () const const

bool	isWidgetType () const const

bool	isWindowType () const const

void	killTimer (int id)

virtual const QMetaObject *	metaObject () const const

void	moveToThread (QThread *targetThread)

QString	objectName () const const

void	objectNameChanged (const QString &objectName)

QObject *	parent () const const

QVariant	property (const char *name) const const

	Q_CLASSINFO (Name, Value)

	Q_EMIT Q_EMIT

	Q_ENUM (...)

	Q_ENUM_NS (...)

	Q_ENUMS (...)

	Q_FLAG (...)

	Q_FLAG_NS (...)

	Q_FLAGS (...)

	Q_GADGET Q_GADGET

	Q_GADGET_EXPORT (EXPORT_MACRO)

	Q_INTERFACES (...)

	Q_INVOKABLE Q_INVOKABLE

	Q_MOC_INCLUDE Q_MOC_INCLUDE

	Q_NAMESPACE Q_NAMESPACE

	Q_NAMESPACE_EXPORT (EXPORT_MACRO)

	Q_OBJECT Q_OBJECT

	Q_PROPERTY (...)

	Q_REVISION Q_REVISION

	Q_SET_OBJECT_NAME (Object)

	Q_SIGNAL Q_SIGNAL

	Q_SIGNALS Q_SIGNALS

	Q_SLOT Q_SLOT

	Q_SLOTS Q_SLOTS

T	qobject_cast (const QObject *object)

T	qobject_cast (QObject *object)

	QT_NO_NARROWING_CONVERSIONS_IN_CONNECT QT_NO_NARROWING_CONVERSIONS_IN_CONNECT

void	removeEventFilter (QObject *obj)

void	setObjectName (const QString &name)

void	setObjectName (QAnyStringView name)

void	setParent (QObject *parent)

bool	setProperty (const char *name, const QVariant &value)

bool	setProperty (const char *name, QVariant &&value)

bool	signalsBlocked () const const

int	startTimer (int interval, Qt::TimerType timerType)

int	startTimer (std::chrono::milliseconds interval, Qt::TimerType timerType)

QThread *	thread () const const

Public Member Functions inherited from QQmlParserStatus

Protected Member Functions
bool	eventFilter (QObject watched, QEvent event) override

Protected Member Functions inherited from QObject
virtual void	childEvent (QChildEvent *event)

virtual void	connectNotify (const QMetaMethod &signal)

virtual void	customEvent (QEvent *event)

virtual void	disconnectNotify (const QMetaMethod &signal)

bool	isSignalConnected (const QMetaMethod &signal) const const

int	receivers (const char *signal) const const

QObject *	sender () const const

int	senderSignalIndex () const const

virtual void	timerEvent (QTimerEvent *event)

Additional Inherited Members
Public Types inherited from QObject
typedef	QObjectList

Static Public Member Functions inherited from QObject
QMetaObject::Connection	connect (const QObject sender, const char signal, const QObject receiver, const char method, Qt::ConnectionType type)

QMetaObject::Connection	connect (const QObject sender, const QMetaMethod &signal, const QObject receiver, const QMetaMethod &method, Qt::ConnectionType type)

QMetaObject::Connection	connect (const QObject sender, PointerToMemberFunction signal, const QObject context, Functor functor, Qt::ConnectionType type)

QMetaObject::Connection	connect (const QObject sender, PointerToMemberFunction signal, const QObject receiver, PointerToMemberFunction method, Qt::ConnectionType type)

QMetaObject::Connection	connect (const QObject *sender, PointerToMemberFunction signal, Functor functor)

bool	disconnect (const QMetaObject::Connection &connection)

bool	disconnect (const QObject sender, const char signal, const QObject receiver, const char method)

bool	disconnect (const QObject sender, const QMetaMethod &signal, const QObject receiver, const QMetaMethod &method)

bool	disconnect (const QObject sender, PointerToMemberFunction signal, const QObject receiver, PointerToMemberFunction method)

QString	tr (const char sourceText, const char disambiguation, int n)

Detailed Description

Handles scrolling for a Flickable and 2 attached ScrollBars.

WheelHandler filters events from a Flickable, a vertical ScrollBar and a horizontal ScrollBar. Wheel and KeyPress events (when keyNavigationEnabled is true) are used to scroll the Flickable. When filterMouseEvents is true, WheelHandler blocks mouse button input from reaching the Flickable and sets the interactive property of the scrollbars to false when touch input is used.

Wheel event handling behavior:

Pixel delta is ignored unless angle delta is not available because pixel delta scrolling is too slow. Qt Widgets doesn't use pixel delta either, so the default scroll speed should be consistent with Qt Widgets.
When using angle delta, scroll using the step increments defined by verticalStepSize and horizontalStepSize.
When one of the keyboard modifiers in pageScrollModifiers is used, scroll by pages.
When using a device that doesn't use 120 angle delta unit increments such as a touchpad, the verticalStepSize, horizontalStepSize and page increments (if using page scrolling) will be multiplied by angle delta / 120 to keep scrolling smooth.
If scrolling has happened in the last 400ms, use an internal QQuickItem stacked over the Flickable's contentItem to catch wheel events and use those wheel events to scroll, if possible. This prevents controls inside the Flickable's contentItem that allow scrolling to change the value (e.g., Sliders, SpinBoxes) from conflicting with scrolling the page.

Common usage with a Flickable:

/* SPDX-FileCopyrightText: 2021 Noah Davis <noahadvs@gmail.com>
 * SPDX-License-Identifier: LGPL-2.1-only OR LGPL-3.0-only OR LicenseRef-KDE-Accepted-LGPL
 */
 
import QtQuick
import QtQuick.Controls as QQC2
import org.kde.kirigami as Kirigami
 
QQC2.ApplicationWindow {
    id: root
 
    width: flickable.implicitWidth
    height: flickable.implicitHeight
    visible: true
 
    Flickable {
        id: flickable
 
        anchors.fill: parent
        implicitWidth: wheelHandler.horizontalStepSize * 10 + leftMargin + rightMargin
        implicitHeight: wheelHandler.verticalStepSize * 10 + topMargin + bottomMargin
 
        leftMargin: QQC2.ScrollBar.vertical.visible && QQC2.ScrollBar.vertical.mirrored ? QQC2.ScrollBar.vertical.width : 0
        rightMargin: QQC2.ScrollBar.vertical.visible && !QQC2.ScrollBar.vertical.mirrored ? QQC2.ScrollBar.vertical.width : 0
        bottomMargin: QQC2.ScrollBar.horizontal.visible ? QQC2.ScrollBar.horizontal.height : 0
 
        contentWidth: contentItem.childrenRect.width
        contentHeight: contentItem.childrenRect.height
 
        Kirigami.WheelHandler {
            id: wheelHandler
            target: flickable
            filterMouseEvents: true
            keyNavigationEnabled: true
        }
 
        QQC2.ScrollBar.vertical: QQC2.ScrollBar {
            parent: flickable.parent
            height: flickable.height - flickable.topMargin - flickable.bottomMargin
            x: mirrored ? 0 : flickable.width - width
            y: flickable.topMargin
            active: flickable.QQC2.ScrollBar.horizontal.active
            stepSize: wheelHandler.verticalStepSize / flickable.contentHeight
        }
 
        QQC2.ScrollBar.horizontal: QQC2.ScrollBar {
            parent: flickable.parent
            width: flickable.width - flickable.leftMargin - flickable.rightMargin
            x: flickable.leftMargin
            y: flickable.height - height
            active: flickable.QQC2.ScrollBar.vertical.active
            stepSize: wheelHandler.horizontalStepSize / flickable.contentWidth
        }
 
        Grid { // Example content
            columns: Math.sqrt(visibleChildren.length)
            Repeater {
                model: 1000
                delegate: Rectangle {
                    implicitWidth: wheelHandler.horizontalStepSize
                    implicitHeight: wheelHandler.verticalStepSize
                    gradient: Gradient {
                        orientation: index % 2 ? Gradient.Vertical : Gradient.Horizontal
                        GradientStop { position: 0; color: Qt.rgba(Math.random(), Math.random(), Math.random(), 1) }
                        GradientStop { position: 1; color: Qt.rgba(Math.random(), Math.random(), Math.random(), 1) }
                    }
                }
            }
        }
    }
}

Common usage inside of a ScrollView template:

/* SPDX-FileCopyrightText: 2021 Noah Davis <noahadvs@gmail.com>
 * SPDX-License-Identifier: LGPL-2.1-only OR LGPL-3.0-only OR LicenseRef-KDE-Accepted-LGPL
 */
 
import QtQuick
import QtQuick.Templates as T
import QtQuick.Controls as QQC2
import org.kde.kirigami as Kirigami
 
T.ScrollView {
    id: control
 
    implicitWidth: Math.max(implicitBackgroundWidth + leftInset + rightInset,
                            contentWidth + leftPadding + rightPadding)
    implicitHeight: Math.max(implicitBackgroundHeight + topInset + bottomInset,
                             contentHeight + topPadding + bottomPadding)
 
    leftPadding: mirrored && T.ScrollBar.vertical.visible && !Kirigami.Settings.isMobile ? T.ScrollBar.vertical.width : 0
    rightPadding: !mirrored && T.ScrollBar.vertical.visible && !Kirigami.Settings.isMobile ? T.ScrollBar.vertical.width : 0
    bottomPadding: T.ScrollBar.horizontal.visible && !Kirigami.Settings.isMobile ? T.ScrollBar.horizontal.height : 0
 
    data: [
        Kirigami.WheelHandler {
            id: wheelHandler
            target: control.contentItem
        }
    ]
 
    T.ScrollBar.vertical: QQC2.ScrollBar {
        parent: control
        x: control.mirrored ? 0 : control.width - width
        y: control.topPadding
        height: control.availableHeight
        active: control.T.ScrollBar.horizontal.active
        stepSize: wheelHandler.verticalStepSize / control.contentHeight
    }
 
    T.ScrollBar.horizontal: QQC2.ScrollBar {
        parent: control
        x: control.leftPadding
        y: control.height - height
        width: control.availableWidth
        active: control.T.ScrollBar.vertical.active
        stepSize: wheelHandler.horizontalStepSize / control.contentWidth
    }
}

Definition at line 179 of file wheelhandler.h.

Property Documentation

◆ blockTargetWheel

bool WheelHandler::blockTargetWheel

This property holds whether the WheelHandler blocks all wheel events from reaching the Flickable.

When this property is false, scrolling the Flickable with WheelHandler will only block an event from reaching the Flickable if the Flickable is actually scrolled by WheelHandler.

NOTE: Wheel events created by touchpad gestures with pixel deltas will always be accepted no matter what. This is because they will cause the Flickable to jump back to where scrolling started unless the events are always accepted before they reach the Flickable.

The default value is true.

Definition at line 268 of file wheelhandler.h.

◆ filterMouseEvents

bool WheelHandler::filterMouseEvents

readwrite

This property holds whether the WheelHandler filters mouse events like a Qt Quick Controls ScrollView would.

Touch events are allowed to flick the view and they make the scrollbars not interactive.

Mouse events are not allowed to flick the view and they make the scrollbars interactive.

Hover events on the scrollbars and wheel events on anything also make the scrollbars interactive when this property is set to true.

The default value is false.

Since: KDE Frameworks 5.89

Definition at line 236 of file wheelhandler.h.

◆ horizontalStepSize

qreal WheelHandler::horizontalStepSize

readwrite

This property holds the horizontal step size.

The default value is equivalent to 20 * Qt.styleHints.wheelScrollLines. This is consistent with the default increment for QScrollArea.

See also: verticalStepSize

Since: KDE Frameworks 5.89

Definition at line 210 of file wheelhandler.h.

◆ keyNavigationEnabled

bool WheelHandler::keyNavigationEnabled

readwrite

This property holds whether the WheelHandler handles keyboard scrolling.

Left arrow scrolls a step to the left.
Right arrow scrolls a step to the right.
Up arrow scrolls a step upwards.
Down arrow scrolls a step downwards.
PageUp scrolls to the previous page.
PageDown scrolls to the next page.
Home scrolls to the beginning.
End scrolls to the end.
When Alt is held, scroll horizontally when using PageUp, PageDown, Home or End.

The default value is false.

Since: KDE Frameworks 5.89

Definition at line 255 of file wheelhandler.h.

◆ pageScrollModifiers

Qt::KeyboardModifiers WheelHandler::pageScrollModifiers

readwrite

This property holds the keyboard modifiers that will be used to start page scrolling.

The default value is equivalent to Qt.ControlModifier | Qt.ShiftModifier. This matches QScrollBar, which uses QAbstractSlider behavior.

Since: KDE Frameworks 5.89

Definition at line 220 of file wheelhandler.h.

◆ scrollFlickableTarget

bool WheelHandler::scrollFlickableTarget

This property holds whether the WheelHandler can use wheel events to scroll the Flickable.

The default value is true.

Definition at line 275 of file wheelhandler.h.

◆ target

QML_ELEMENTQQuickItem * WheelHandler::target

readwrite

This property holds the Qt Quick Flickable that the WheelHandler will control.

Definition at line 188 of file wheelhandler.h.

◆ verticalStepSize

qreal WheelHandler::verticalStepSize

readwrite

This property holds the vertical step size.

The default value is equivalent to 20 * Qt.styleHints.wheelScrollLines. This is consistent with the default increment for QScrollArea.

See also: horizontalStepSize

Since: KDE Frameworks 5.89

Definition at line 199 of file wheelhandler.h.

Constructor & Destructor Documentation

◆ WheelHandler()

WheelHandler::WheelHandler ( QObject * parent = nullptr )

explicit

Definition at line 91 of file wheelhandler.cpp.

◆ ~WheelHandler()

WheelHandler::~WheelHandler ( )

override

Definition at line 118 of file wheelhandler.cpp.

Member Function Documentation

◆ eventFilter()

bool WheelHandler::eventFilter	(	QObject *	watched,
		QEvent *	event )

overrideprotectedvirtual

Reimplemented from QObject.

Definition at line 573 of file wheelhandler.cpp.

◆ filterMouseEvents()

bool WheelHandler::filterMouseEvents ( ) const

Definition at line 357 of file wheelhandler.cpp.

◆ horizontalStepSize()

qreal WheelHandler::horizontalStepSize ( ) const

Definition at line 308 of file wheelhandler.cpp.

◆ keyNavigationEnabled()

bool WheelHandler::keyNavigationEnabled ( ) const

Definition at line 371 of file wheelhandler.cpp.

◆ pageScrollModifiers()

Qt::KeyboardModifiers WheelHandler::pageScrollModifiers ( ) const

Definition at line 338 of file wheelhandler.cpp.

◆ resetHorizontalStepSize()

void WheelHandler::resetHorizontalStepSize ( )

Definition at line 328 of file wheelhandler.cpp.

◆ resetPageScrollModifiers()

void WheelHandler::resetPageScrollModifiers ( )

Definition at line 352 of file wheelhandler.cpp.

◆ resetVerticalStepSize()

void WheelHandler::resetVerticalStepSize ( )

Definition at line 298 of file wheelhandler.cpp.

◆ scrollDown()

bool WheelHandler::scrollDown ( qreal stepSize = -1 )

Scroll down one step.

If the stepSize parameter is less than 0, the verticalStepSize will be used.

returns true if the contentItem was moved.

Since: KDE Frameworks 5.89

Definition at line 540 of file wheelhandler.cpp.

◆ scrollLeft()

bool WheelHandler::scrollLeft ( qreal stepSize = -1 )

Scroll left one step.

If the stepSize parameter is less than 0, the horizontalStepSize will be used.

returns true if the contentItem was moved.

Since: KDE Frameworks 5.89

Definition at line 551 of file wheelhandler.cpp.

◆ scrollRight()

bool WheelHandler::scrollRight ( qreal stepSize = -1 )

Scroll right one step.

If the stepSize parameter is less than 0, the horizontalStepSize will be used.

returns true if the contentItem was moved.

Since: KDE Frameworks 5.89

Definition at line 562 of file wheelhandler.cpp.

◆ scrollUp()

bool WheelHandler::scrollUp ( qreal stepSize = -1 )

Scroll up one step.

If the stepSize parameter is less than 0, the verticalStepSize will be used.

returns true if the contentItem was moved.

Since: KDE Frameworks 5.89

Definition at line 529 of file wheelhandler.cpp.

◆ setFilterMouseEvents()

void WheelHandler::setFilterMouseEvents ( bool enabled )

Definition at line 362 of file wheelhandler.cpp.

◆ setHorizontalStepSize()

void WheelHandler::setHorizontalStepSize ( qreal stepSize )

Definition at line 313 of file wheelhandler.cpp.

◆ setKeyNavigationEnabled()

void WheelHandler::setKeyNavigationEnabled ( bool enabled )

Definition at line 376 of file wheelhandler.cpp.

◆ setPageScrollModifiers()

void WheelHandler::setPageScrollModifiers ( Qt::KeyboardModifiers modifiers )

Definition at line 343 of file wheelhandler.cpp.

◆ setTarget()

void WheelHandler::setTarget ( QQuickItem * target )

Definition at line 128 of file wheelhandler.cpp.

◆ setVerticalStepSize()

void WheelHandler::setVerticalStepSize ( qreal stepSize )

Definition at line 283 of file wheelhandler.cpp.

◆ target()

QQuickItem * WheelHandler::target ( ) const

Definition at line 123 of file wheelhandler.cpp.

◆ verticalStepSize()

qreal WheelHandler::verticalStepSize ( ) const

Definition at line 278 of file wheelhandler.cpp.

◆ wheel

void WheelHandler::wheel ( KirigamiWheelEvent * wheel )

signal

This signal is emitted when a wheel event reaches the event filter, just before scrolling is handled.

Accepting the wheel event in the onWheel signal handler prevents scrolling from happening.

The documentation for this class was generated from the following files:

KDE's Doxygen guidelines are available online.

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About Kirigami2

WheelHandler

Properties

Signals

Public Member Functions

Protected Member Functions

Additional Inherited Members

Detailed Description

Property Documentation

◆ blockTargetWheel

◆ filterMouseEvents

◆ horizontalStepSize

◆ keyNavigationEnabled

◆ pageScrollModifiers

◆ scrollFlickableTarget

◆ target

◆ verticalStepSize

Constructor & Destructor Documentation

◆ WheelHandler()

◆ ~WheelHandler()

Member Function Documentation

◆ eventFilter()

◆ filterMouseEvents()

◆ horizontalStepSize()

◆ keyNavigationEnabled()

◆ pageScrollModifiers()

◆ resetHorizontalStepSize()

◆ resetPageScrollModifiers()

◆ resetVerticalStepSize()

◆ scrollDown()

◆ scrollLeft()

◆ scrollRight()

◆ scrollUp()

◆ setFilterMouseEvents()

◆ setHorizontalStepSize()

◆ setKeyNavigationEnabled()

◆ setPageScrollModifiers()

◆ setTarget()

◆ setVerticalStepSize()

◆ target()

◆ verticalStepSize()

◆ wheel