StackView: provide better warnings and errors

Check for valid URLs and test object types. Throw warnings when
appropriate instead of crashing later.

Task-number: QTBUG-59634
Change-Id: Ia269dc8afd31b618f1ff7aec94d684029cb78244
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

1 files changed, 16 insertions, 3 deletions

diff --git a/src/quicktemplates2/qquickstackelement.cpp b/src/quicktemplates2/qquickstackelement.cpp
index aace170b..27331afe 100644
--- a/src/quicktemplates2/qquickstackelement.cpp
+++ b/src/quicktemplates2/qquickstackelement.cpp
@@ -122,17 +122,30 @@ QQuickStackElement::~QQuickStackElement()
     delete context;
 }
 
-QQuickStackElement *QQuickStackElement::fromString(const QString &str, QQuickStackView *view)
+QQuickStackElement *QQuickStackElement::fromString(const QString &str, QQuickStackView *view, QString *error)
 {
+    QUrl url(str);
+    if (!url.isValid()) {
+        *error = QStringLiteral("invalid url: ") + str;
+        return nullptr;
+    }
+
     QQuickStackElement *element = new QQuickStackElement;
-    element->component = new QQmlComponent(qmlEngine(view), QUrl(str), view);
+    element->component = new QQmlComponent(qmlEngine(view), url, view);
     element->ownComponent = true;
     return element;
 }
 
-QQuickStackElement *QQuickStackElement::fromObject(QObject *object, QQuickStackView *view)
+QQuickStackElement *QQuickStackElement::fromObject(QObject *object, QQuickStackView *view, QString *error)
 {
     Q_UNUSED(view);
+    QQmlComponent *component = qobject_cast<QQmlComponent *>(object);
+    QQuickItem *item = qobject_cast<QQuickItem *>(object);
+    if (!component && !item) {
+        *error = QQmlMetaType::prettyTypeName(object) + QStringLiteral(" is not supported. Must be Item or Component.");
+        return nullptr;
+    }
+
     QQuickStackElement *element = new QQuickStackElement;
     element->component = qobject_cast<QQmlComponent *>(object);
     element->item = qobject_cast<QQuickItem *>(object);