1 files changed, 90 insertions, 0 deletions
diff --git a/src/qml/qmlcontrolproxy.h b/src/qml/qmlcontrolproxy.h
new file mode 100644
index 0000000000..5b2493714a
--- /dev/null
+++ b/src/qml/qmlcontrolproxy.h
@@ -0,0 +1,90 @@
+#pragma once
+
+#include <QObject>
+#include <QQmlParserStatus>
+#include <QtQml>
+#include <memory>
+
+#include "control/controlproxy.h"
+
+namespace mixxx {
+namespace skin {
+namespace qml {
+
+class QmlControlProxy : public QObject, public QQmlParserStatus {
+    Q_OBJECT
+    Q_INTERFACES(QQmlParserStatus)
+    // TODO: The REQUIRED flag only exists in Qt 5.14 and later. Once we
+    // require that as minimum dependency, add it to the group and key
+    // properties.
+    Q_PROPERTY(QString group READ getGroup WRITE setGroup NOTIFY groupChanged)
+    Q_PROPERTY(QString key READ getKey WRITE setKey NOTIFY keyChanged)
+    Q_PROPERTY(QString keyValid READ isKeyValid NOTIFY keyValidChanged)
+    Q_PROPERTY(QString initialized READ isInitialized NOTIFY initializedChanged)
+    Q_PROPERTY(double value READ getValue WRITE setValue NOTIFY valueChanged)
+    Q_PROPERTY(double parameter READ getParameter WRITE setParameter NOTIFY parameterChanged)
+
+  public:
+    explicit QmlControlProxy(QObject* parent = nullptr);
+
+    /// Implementing the QQmlParserStatus interface requires overriding this
+    /// method, but we don't need it.
+    // Invoked after class creation, but before any properties have been set.
+    void classBegin() override{};
+
+    /// QML cannot pass arguments to C++ constructors so this class needs to
+    /// rely on the QML object setting the group and key properties to
+    /// initialize the ControlProxy. We want to deplay the initialization of
+    /// the underlying ControlProxy until the object has been fully created and
+    /// all properties (group and key in particular) have been set.  Perform
+    /// some initialization here now that the object is fully created.
+    void componentComplete() override;
+
+    void setGroup(const QString& group);
+    const QString& getGroup() const;
+
+    void setKey(const QString& key);
+    const QString& getKey() const;
+
+    void setValue(double newValue);
+    double getValue() const;
+
+    void setParameter(double newValue);
+    double getParameter() const;
+
+    bool isKeyValid() const;
+    bool isInitialized() const;
+
+    /// Reset the control to the default value.
+    Q_INVOKABLE void reset();
+
+  signals:
+    void groupChanged(const QString& group);
+    void keyChanged(const QString& key);
+    void keyValidChanged(bool valid);
+    void initializedChanged(bool initialized);
+    void valueChanged(double newValue);
+    void parameterChanged(double newParameter);
+
+  private slots:
+    /// Emits both the valueChanged and parameterChanged signals
+    void slotControlProxyValueChanged(double newValue);
+
+  private:
+    /// (Re-)Initializes or resets the pointer to the underlying control proxy.
+    /// Called for the first time when component construction has been
+    /// completed. From that moment on, it's called whenever the group or key
+    /// changes.
+    void reinitializeFromKey();
+
+    ConfigKey m_coKey;
+
+    /// Set to true in the componentComplete() method, which is called when the
+    /// QML object creation is complete.
+    bool m_isComponentComplete;
+    std::unique_ptr<ControlProxy> m_pControlProxy;
+};
+
+} // namespace qml
+} // namespace skin
+} // namespace mixxx