QmlDesigner: Add registerPropertyMap to StudioWelcome

This allows to easily register a singleton similar to
context properties.

Change-Id: I0c391165473a949e7fd09d907e3a0752c23ba62d
Reviewed-by: Henning Gründl <henning.gruendl@qt.io>

src/plugins/qmldesignerbase/utils/studioquickwidget.cpp

@@ -3,6 +3,7 @@
 
 #include "studioquickwidget.h"
 
+#include <QQuickItem>
 #include <QVBoxLayout>
 #include <QtQml/QQmlEngine>
 
@@ -58,3 +59,26 @@ QList<QQmlError> StudioQuickWidget::errors() const
 {
     return m_quickWidget->errors();
 }
+
+StudioPropertyMap *StudioQuickWidget::registerPropertyMap(const QByteArray &name)
+{
+    StudioPropertyMap *map = new StudioPropertyMap(this);
+    [[maybe_unused]] const int typeIndex = qmlRegisterSingletonType<StudioPropertyMap>(
+        name.data(), 1, 0, name.data(), [map](QQmlEngine *, QJSEngine *) { return map; });
+    return map;
+}
+
+QQuickWidget *StudioQuickWidget::quickWidget() const
+{
+    return m_quickWidget;
+}
+
+StudioPropertyMap::StudioPropertyMap(QObject *parent)
+    : QQmlPropertyMap(parent)
+{}
+
+void StudioPropertyMap::setProperties(const QList<PropertyPair> &properties)
+{
+    for (const PropertyPair &pair : properties)
+        insert(pair.name, pair.value);
+}

src/plugins/qmldesignerbase/utils/studioquickwidget.h

@@ -6,8 +6,23 @@
 #include "../qmldesignerbase_global.h"
 
 #include <QObject>
+#include <QQmlPropertyMap>
 #include <QtQuickWidgets/QQuickWidget>
 
+class QMLDESIGNERBASE_EXPORT StudioPropertyMap : public QQmlPropertyMap
+{
+public:
+    struct PropertyPair
+    {
+        QString name;
+        QVariant value;
+    };
+
+    explicit StudioPropertyMap(QObject *parent = 0);
+
+    void setProperties(const QList<PropertyPair> &properties);
+};
+
 class QMLDESIGNERBASE_EXPORT StudioQuickWidget : public QWidget
 {
     Q_OBJECT
@@ -29,6 +44,9 @@ public:
 
     QList<QQmlError> errors() const;
 
+    StudioPropertyMap *registerPropertyMap(const QByteArray &name);
+    QQuickWidget *quickWidget() const;
+
 private:
     QQuickWidget *m_quickWidget = nullptr;
 };