widgets: add wrapper components and managers

src/widgets/marginwrapper.hpp

@@ -0,0 +1,75 @@
+#pragma once
+
+#include <qobject.h>
+#include <qqmlintegration.h>
+#include <qtmetamacros.h>
+#include <qtypes.h>
+
+#include "wrapper.hpp"
+
+namespace qs::widgets {
+
+///! Helper object for applying sizes and margins to a single child item.
+/// > [!NOTE] MarginWrapperManager is an extension of @@WrapperManager.
+/// > You should read its documentation to understand wrapper types.
+///
+/// MarginWrapperManager can be used to apply margins to a child item,
+/// in addition to handling the size / implicit size relationship
+/// between the parent and the child. @@WrapperItem and @@WrapperRectangle
+/// exist for Item and Rectangle implementations respectively.
+///
+/// > [!WARNING] MarginWrapperManager based types set the child item's
+/// > @@QtQuick.Item.x, @@QtQuick.Item.y, @@QtQuick.Item.width, @@QtQuick.Item.height
+/// > or @@QtQuick.Item.anchors properties. Do not set them yourself,
+/// > instead set @@Item.implicitWidth and @@Item.implicitHeight.
+///
+/// ### Implementing a margin wrapper type
+/// Follow the directions in @@WrapperManager$'s documentation, and or
+/// alias the @@margin property if you wish to expose it.
+class MarginWrapperManager: public WrapperManager {
+	Q_OBJECT;
+	// clang-format off
+	/// The minimum margin between the child item and the parent item's edges.
+	/// Defaults to 0.
+	Q_PROPERTY(qreal margin READ margin WRITE setMargin NOTIFY marginChanged FINAL);
+	/// If the child item should be resized larger than its implicit size if
+	/// the parent is resized larger than its implicit size. Defaults to false.
+	Q_PROPERTY(bool resizeChild READ resizeChild WRITE setResizeChild NOTIFY resizeChildChanged FINAL);
+	// clang-format on
+	QML_ELEMENT;
+
+public:
+	explicit MarginWrapperManager(QObject* parent = nullptr);
+
+	void componentComplete() override;
+
+	[[nodiscard]] qreal margin() const;
+	void setMargin(qreal margin);
+
+	[[nodiscard]] bool resizeChild() const;
+	void setResizeChild(bool resizeChild);
+
+signals:
+	void marginChanged();
+	void resizeChildChanged();
+
+private slots:
+	void onChildChanged();
+	void onWrapperWidthChanged();
+	void onWrapperHeightChanged();
+	void onChildImplicitWidthChanged();
+	void onChildImplicitHeightChanged();
+
+private:
+	void updateGeometry();
+
+	[[nodiscard]] qreal targetChildX() const;
+	[[nodiscard]] qreal targetChildY() const;
+	[[nodiscard]] qreal targetChildWidth() const;
+	[[nodiscard]] qreal targetChildHeight() const;
+
+	qreal mMargin = 0;
+	bool mResizeChild = false;
+};
+
+} // namespace qs::widgets