core/boundcomponent: add BoundComponent

src/core/boundcomponent.hpp

@@ -0,0 +1,125 @@
+#pragma once
+
+#include <qmetaobject.h>
+#include <qobject.h>
+#include <qqmlcomponent.h>
+#include <qqmlparserstatus.h>
+#include <qquickitem.h>
+#include <qsignalmapper.h>
+#include <qtmetamacros.h>
+
+#include "incubator.hpp"
+
+///! Component loader that allows setting initial properties.
+/// Component loader that allows setting initial properties, primarily useful for
+/// escaping cyclic dependency errors.
+///
+/// Properties defined on the BoundComponent will be applied to its loaded component,
+/// including required properties, and will remain reactive. Functions created with
+/// the names of signal handlers will also be attached to signals of the loaded component.
+///
+/// ```qml {filename="MyComponent.qml"}
+/// MouseArea {
+///   required property color color;
+///   width: 100
+///   height: 100
+///
+///   Rectangle {
+///     anchors.fill: parent
+///     color: parent.color
+///   }
+/// }
+/// ```
+///
+/// ```qml
+/// BoundComponent {
+///   source: "MyComponent.qml"
+///
+///   // this is the same as assigning to `color` on MyComponent if loaded normally.
+///   property color color: "red";
+///
+///   // this will be triggered when the `clicked` signal from the MouseArea is sent.
+///   function onClicked() {
+///     color = "blue";
+///   }
+/// }
+/// ```
+class BoundComponent: public QQuickItem {
+	Q_OBJECT;
+	// clang-format off
+	/// The loaded component. Will be null until it has finished loading.
+	Q_PROPERTY(QObject* item READ item NOTIFY loaded);
+	/// The source to load, as a Component.
+	Q_PROPERTY(QQmlComponent* sourceComponent READ sourceComponent WRITE setSourceComponent NOTIFY sourceComponentChanged);
+	/// The source to load, as a Url.
+	Q_PROPERTY(QString source READ source WRITE setSource NOTIFY sourceChanged);
+	/// If property values should be bound after they are initially set. Defaults to `true`.
+	Q_PROPERTY(bool bindValues READ bindValues WRITE setBindValues NOTIFY bindValuesChanged);
+	Q_PROPERTY(qreal implicitWidth READ implicitWidth NOTIFY implicitWidthChanged);
+	Q_PROPERTY(qreal implicitHeight READ implicitHeight NOTIFY implicitHeightChanged);
+	// clang-format on
+	QML_ELEMENT;
+
+public:
+	explicit BoundComponent(QQuickItem* parent = nullptr): QQuickItem(parent) {}
+
+	void componentComplete() override;
+
+	[[nodiscard]] QObject* item() const;
+
+	[[nodiscard]] QQmlComponent* sourceComponent() const;
+	void setSourceComponent(QQmlComponent* sourceComponent);
+
+	[[nodiscard]] QString source() const;
+	void setSource(QString source);
+
+	[[nodiscard]] bool bindValues() const;
+	void setBindValues(bool bindValues);
+
+signals:
+	void loaded();
+	void sourceComponentChanged();
+	void sourceChanged();
+	void bindValuesChanged();
+
+private slots:
+	void onComponentDestroyed();
+	void onIncubationCompleted();
+	void onIncubationFailed();
+	void updateSize();
+	void updateImplicitSize();
+
+private:
+	void disconnectComponent();
+	void tryCreate();
+
+	QString mSource;
+	bool mBindValues = true;
+	QQmlComponent* mComponent = nullptr;
+	bool ownsComponent = false;
+	QsQmlIncubator* incubator = nullptr;
+	QObject* object = nullptr;
+	QQuickItem* mItem = nullptr;
+	bool componentCompleted = false;
+};
+
+class BoundComponentPropertyProxy: public QObject {
+	Q_OBJECT;
+
+public:
+	BoundComponentPropertyProxy(
+	    QObject* from,
+	    QObject* to,
+	    QMetaProperty fromProperty,
+	    QMetaProperty toProperty
+	);
+
+public slots:
+	void onNotified();
+
+private:
+	QObject* from;
+	QObject* to;
+	QMetaProperty fromProperty;
+	QMetaProperty toProperty;
+};