qqstylekitdelegate.cpp

Go to the documentation of this file.

// Copyright (C) 2026 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
 
#include "qqstylekitdelegate_p.h"
#include "qqstylekitcontrolproperties_p.h"
 
#include <QtQuick/private/qquickrectangle_p.h>
#include <QtQuick/private/qquickimplicitsizeitem_p_p.h>
#include <QtQuickControls2Impl/private/qquickcolorimage_p.h>
 
QT_BEGIN_NAMESPACE
 
/*!
    \qmltype StyledItem
    \inqmlmodule Qt.labs.StyleKit
    \inherits Item
    \brief Renders a DelegateStyle.
 
    StyledItem renders a \l DelegateStyle. It reads properties such as
    \l {DelegateStyle::color}{color},
    \l {DelegateStyle::border}{border},
    \l {DelegateStyle::gradient}{gradient}, and
    \l {DelegateStyle::image}{image}, and creates the corresponding
    visual elements internally.
 
    If the \l {DelegateStyle::delegate}{delegate} set on a DelegateStyle
    is \c null (the default), StyledItem will automatically be used for rendering.
 
    A custom \l {DelegateStyle::delegate}{delegate} can be set to
    any Item. But combined with a StyledItem, you can retain
    the default rendering while adding overlay, underlay, or shader effects.
    The following snippet shows how to draw an extra Item on top of the
    default delegate:
 
    \snippet StyledItemOverlay.qml overlay
 
    \labs
 
    For more examples of overlays, underlays and shader effects, see the
    \l{StyleKit Quick Controls Example}.
 
    \sa DelegateStyle, {DelegateStyle::delegate}{delegate}, {DelegateStyle::data}{data}
*/
 
/*!
    \qmlproperty DelegateStyle StyledItem::delegateStyle
 
    The \l DelegateStyle that this item renders.
 
    This property is \l {Required Properties}{required}. When
    StyledItem is the root item of a
    \l {DelegateStyle::delegate}{delegate}, it is set automatically.
    But when used as a child inside a custom delegate, it must be set
    explicitly.
 
    The following snippet uses a custom delegate that draws a star
    underneath the default slider handle. Since the root item is not
    a StyledItem, it declares a \l {Required Properties}{required}
    property \c {delegateStyle} (which is assigned automatically), and
    forwards it to the child StyledItem:
 
    \snippet StyledItemUnderlay.qml underlay
 
    \sa DelegateStyle, {DelegateStyle::delegate}{delegate}, {DelegateStyle::data}{data}
*/
 
QQStyleKitDelegate::QQStyleKitDelegate(QQuickItem *parent)
    : QQuickImplicitSizeItem(*new QQuickImplicitSizeItemPrivate, parent)
{
}
 
QQStyleKitDelegateProperties *QQStyleKitDelegate::delegateStyle() const
{
    return m_delegateProperties;
}
 
void QQStyleKitDelegate::setDelegateStyle(QQStyleKitDelegateProperties *delegateStyle)
{
    if (m_delegateProperties == delegateStyle)
        return;
 
    if (m_delegateProperties)
        disconnect(m_delegateProperties, nullptr, this, nullptr);
 
    m_delegateProperties = delegateStyle;
 
    if (!qmlEngine(this)) {
        qmlWarning(this) << "Unable to draw delegate: no QQmlEngine found";
        return;
    }
 
    maybeCreateColor();
    maybeCreateGradient();
    maybeCreateImage();
    updateImplicitSize();
 
    connect(m_delegateProperties, &QQStyleKitDelegateProperties::widthChanged, this, &QQStyleKitDelegate::updateImplicitSize);
    connect(m_delegateProperties, &QQStyleKitDelegateProperties::heightChanged, this, &QQStyleKitDelegate::updateImplicitSize);
 
    emit delegateStyleChanged();
}
 
void QQStyleKitDelegate::updateImplicitSize()
{
    if (!m_delegateProperties)
        return;
 
    /* The implicit size of this item is determined by the following priority:
     * 1. The width/height set on DelegateStyle (clamped to minimumWidth/minimumHeight)
     * 2. The implicit size of the image overlay (if present)
     * 3. Zero */
    const qreal widthInStyle = qMax(m_delegateProperties->minimumWidth(), m_delegateProperties->width());
    const qreal heightInStyle = qMax(m_delegateProperties->minimumHeight(), m_delegateProperties->height());
    setImplicitWidth(widthInStyle > 0 || !m_imageOverlay ? widthInStyle : m_imageOverlay->implicitWidth());
    setImplicitHeight(heightInStyle > 0 || !m_imageOverlay ? heightInStyle : m_imageOverlay->implicitHeight());
}
 
void QQStyleKitDelegate::maybeCreateColor()
{
    if (m_colorOverlay)
        return;
    if (!m_delegateProperties)
        return;
    if (m_delegateProperties->color().alpha() == 0
        && (m_delegateProperties->border()->color().alpha() == 0
            || m_delegateProperties->border()->width() == 0)) {
        // Lazy-create the color rectangle later, if/when needed
        connect(m_delegateProperties, &QQStyleKitDelegateProperties::colorChanged,
                this, &QQStyleKitDelegate::maybeCreateColor, Qt::UniqueConnection);
        connect(m_delegateProperties->border(), &QQStyleKitBorderProperties::colorChanged,
                this, &QQStyleKitDelegate::maybeCreateColor, Qt::UniqueConnection);
        connect(m_delegateProperties->border(), &QQStyleKitBorderProperties::widthChanged,
                this, &QQStyleKitDelegate::maybeCreateColor, Qt::UniqueConnection);
        return;
    }
 
    disconnect(m_delegateProperties, &QQStyleKitDelegateProperties::colorChanged,
            this, &QQStyleKitDelegate::maybeCreateColor);
    disconnect(m_delegateProperties->border(), &QQStyleKitBorderProperties::colorChanged,
            this, &QQStyleKitDelegate::maybeCreateColor);
    disconnect(m_delegateProperties->border(), &QQStyleKitBorderProperties::widthChanged,
            this, &QQStyleKitDelegate::maybeCreateColor);
 
    QQmlEngine *engine = qmlEngine(this);
    Q_ASSERT(engine);
    static QQmlComponent *component = nullptr;
    if (!component || component->engine() != engine) {
        delete component;
        component = new QQmlComponent(engine);
        const auto qmlCode = R"(
            import QtQuick
            Rectangle {
                z: -3
                width: parent.width
                height: parent.height
                color: delegateStyle.color
                opacity: delegateStyle.opacity
                topLeftRadius: delegateStyle.topLeftRadius
                topRightRadius: delegateStyle.topRightRadius
                bottomLeftRadius: delegateStyle.bottomLeftRadius
                bottomRightRadius: delegateStyle.bottomRightRadius
                border.width: delegateStyle.border.width
                border.color: delegateStyle.border.color
            }
        )"_ba;
        component->setData(qmlCode, QUrl());
        Q_ASSERT_X(!component->isError(), __FUNCTION__, component->errorString().toUtf8().constData());
    }
 
    QQmlContext *ctx = QQmlEngine::contextForObject(this);
    m_colorOverlay = qobject_cast<QQuickItem*>(component->beginCreate(ctx));
    Q_ASSERT(m_colorOverlay);
    m_colorOverlay->setParent(this);
    m_colorOverlay->setParentItem(this);
    component->completeCreate();
}
 
void QQStyleKitDelegate::maybeCreateGradient()
{
    /* Unlike a Rectangle, a StyledItem draws both the color and the gradient at
     * the same time. This allows a style to define them independently. That way you can
     * define a common semi-transparent grayscale gradient once for a delegate in the style
     * (e.g for control.background.gradient), and then tint it with different colors for
     * different controls, states, or themes (e.g for button.hovered.background.color). */
    if (m_gradientOverlay)
        return;
    if (!m_delegateProperties)
        return;
    if (!m_delegateProperties->gradient()) {
        connect(m_delegateProperties, &QQStyleKitDelegateProperties::gradientChanged,
                this, &QQStyleKitDelegate::maybeCreateGradient, Qt::UniqueConnection);
        return;
    }
 
    disconnect(m_delegateProperties, &QQStyleKitDelegateProperties::gradientChanged,
               this, &QQStyleKitDelegate::maybeCreateGradient);
 
    QQmlEngine *engine = qmlEngine(this);
    Q_ASSERT(engine);
    static QQmlComponent *component = nullptr;
    if (!component || component->engine() != engine) {
        delete component;
        component = new QQmlComponent(engine);
        const auto qmlCode = R"(
            import QtQuick
            Rectangle {
                z: -2
                width: parent.width
                height: parent.height
                color: "transparent"
                visible: delegateStyle.gradient != null
                gradient: delegateStyle.gradient
                topLeftRadius: delegateStyle.topLeftRadius
                topRightRadius: delegateStyle.topRightRadius
                bottomLeftRadius: delegateStyle.bottomLeftRadius
                bottomRightRadius: delegateStyle.bottomRightRadius
                border.width: delegateStyle.border.width
                border.color: delegateStyle.border.color
            }
        )"_ba;
        component->setData(qmlCode, QUrl());
        Q_ASSERT_X(!component->isError(), __FUNCTION__, component->errorString().toUtf8().constData());
    }
 
    QQmlContext *ctx = QQmlEngine::contextForObject(this);
    m_gradientOverlay = qobject_cast<QQuickItem*>(component->beginCreate(ctx));
    Q_ASSERT(m_gradientOverlay);
    m_gradientOverlay->setParent(this);
    m_gradientOverlay->setParentItem(this);
    component->completeCreate();
}
 
void QQStyleKitDelegate::maybeCreateImage()
{
    if (m_imageOverlay)
        return;
    if (!m_delegateProperties)
        return;
    if (m_delegateProperties->image()->source().isEmpty()
        || m_delegateProperties->image()->color().alpha() == 0) {
        connect(m_delegateProperties->image(), &QQStyleKitImageProperties::sourceChanged,
                this, &QQStyleKitDelegate::maybeCreateImage, Qt::UniqueConnection);
        connect(m_delegateProperties->image(), &QQStyleKitImageProperties::colorChanged,
                this, &QQStyleKitDelegate::maybeCreateImage, Qt::UniqueConnection);
        return;
    }
 
    disconnect(m_delegateProperties->image(), &QQStyleKitImageProperties::sourceChanged,
               this, &QQStyleKitDelegate::maybeCreateImage);
    disconnect(m_delegateProperties->image(), &QQStyleKitImageProperties::colorChanged,
               this, &QQStyleKitDelegate::maybeCreateImage);
 
    QQmlEngine *engine = qmlEngine(this);
    Q_ASSERT(engine);
    static QQmlComponent *component = nullptr;
    if (!component || component->engine() != engine) {
        delete component;
        component = new QQmlComponent(engine);
        const auto qmlCode = R"(
            import QtQuick.Controls.impl
            ColorImage {
                z: -1
                width: parent.width
                height: parent.height
                color: delegateStyle.image.color
                source: delegateStyle.image.source
                fillMode: delegateStyle.image.fillMode
            }
        )"_ba;
        component->setData(qmlCode, QUrl());
        Q_ASSERT_X(!component->isError(), __FUNCTION__, component->errorString().toUtf8().constData());
    }
 
    QQmlContext *ctx = QQmlEngine::contextForObject(this);
    m_imageOverlay = qobject_cast<QQuickItem*>(component->beginCreate(ctx));
    m_imageOverlay->setParent(this);
    m_imageOverlay->setParentItem(this);
    component->completeCreate();
 
    updateImplicitSize();
    connect(m_imageOverlay, &QQuickItem::implicitWidthChanged, this, &QQStyleKitDelegate::updateImplicitSize);
    connect(m_imageOverlay, &QQuickItem::implicitHeightChanged, this, &QQStyleKitDelegate::updateImplicitSize);
}
 
QT_END_NAMESPACE
 
#include "moc_qqstylekitdelegate_p.cpp"