LazyLoader.h

Go to the documentation of this file.

// SPDX-FileCopyrightText: 2026 fuddlesworth
// SPDX-License-Identifier: LGPL-2.1-or-later
 
#pragma once
 
#include <PhosphorShell/phosphorshell_export.h>
 
#include <QPointer>
#include <QQuickItem>
#include <QUrl>
 
QT_BEGIN_NAMESPACE
class QQmlComponent;
class QQmlIncubator;
QT_END_NAMESPACE
 
namespace PhosphorShell {
 
class PHOSPHORSHELL_EXPORT LazyLoader : public QQuickItem
{
    Q_OBJECT
 
    Q_PROPERTY(bool active READ active WRITE setActive NOTIFY activeChanged)
    Q_PROPERTY(
        QQmlComponent* sourceComponent READ sourceComponent WRITE setSourceComponent NOTIFY sourceComponentChanged)
    Q_PROPERTY(QUrl source READ source WRITE setSource NOTIFY sourceChanged)
    Q_PROPERTY(QQuickItem* item READ item NOTIFY itemChanged)
    Q_PROPERTY(Status status READ status NOTIFY statusChanged)
 
public:
    enum Status {
        Null,
        Loading,
        Ready,
        Error
    };
    Q_ENUM(Status)
 
    explicit LazyLoader(QQuickItem* parent = nullptr);
    ~LazyLoader() override;
 
    [[nodiscard]] bool active() const;
    void setActive(bool active);
 
    [[nodiscard]] QQmlComponent* sourceComponent() const;
    void setSourceComponent(QQmlComponent* component);
 
    [[nodiscard]] QUrl source() const;
    void setSource(const QUrl& source);
 
    [[nodiscard]] QQuickItem* item() const;
    [[nodiscard]] Status status() const;
 
Q_SIGNALS:
    void activeChanged();
    void sourceComponentChanged();
    void sourceChanged();
    void itemChanged();
    void statusChanged();
    void loaded();
 
private:
    friend class LazyIncubator;
 
    void startLoading();
    void unload();
    void onIncubatorReady();
 
    bool m_active = false;
    // QPointer because the component is externally owned by the QML
    // scene — a parent reload that destroys the source component must
    // not leave us with a dangling pointer that startLoading would
    // dereference on the next active toggle.
    QPointer<QQmlComponent> m_sourceComponent;
    QQmlComponent* m_ownedComponent = nullptr;
    QUrl m_source;
    QPointer<QQuickItem> m_item;
    QQmlIncubator* m_incubator = nullptr;
    Status m_status = Null;
};
 
} // namespace PhosphorShell