Add API to learn about QQmlBinding's dependencies

Adds a method `dependencies()` to QQmlBinding, that returns a
QVector<QQmlProperty> of all properties the binding depends on. The API is
meant to be used in debugging tools (e.g. in GammaRay).
Also adds a public method subBindings() to QQmlValueTypeProxyBinding in
order to be able to access their dependencies.

Change-Id: Ib833703ec9e632661626c4532b8d73997f38e62b
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

1 files changed, 32 insertions, 0 deletions

diff --git a/src/qml/qml/qqmlbinding.cpp b/src/qml/qml/qqmlbinding.cpp
index 84f30af066..566fbb86ac 100644
--- a/src/qml/qml/qqmlbinding.cpp
+++ b/src/qml/qml/qqmlbinding.cpp
@@ -54,6 +54,7 @@
 
 #include <QVariant>
 #include <QtCore/qdebug.h>
+#include <QVector>
 
 QT_BEGIN_NAMESPACE
 
@@ -579,6 +580,37 @@ void QQmlBinding::getPropertyData(QQmlPropertyData **propertyData, QQmlPropertyD
     }
 }
 
+QVector<QQmlProperty> QQmlBinding::dependencies() const
+{
+    QVector<QQmlProperty> dependencies;
+    if (!m_target.data())
+        return dependencies;
+
+    for (const auto &guardList : { permanentGuards, activeGuards }) {
+        for (QQmlJavaScriptExpressionGuard *guard = guardList.first(); guard; guard = guardList.next(guard)) {
+            if (guard->signalIndex() == -1) // guard's sender is a QQmlNotifier, not a QObject*.
+                continue;
+
+            QObject *senderObject = guard->senderAsObject();
+            if (!senderObject)
+                continue;
+
+            const QMetaObject *senderMeta = senderObject->metaObject();
+            if (!senderMeta)
+                continue;
+
+            for (int i = 0; i < senderMeta->propertyCount(); i++) {
+                QMetaProperty property = senderMeta->property(i);
+                if (property.notifySignalIndex() == QMetaObjectPrivate::signal(senderMeta, guard->signalIndex()).methodIndex()) {
+                    dependencies.push_back(QQmlProperty(senderObject, QString::fromUtf8(senderObject->metaObject()->property(i).name())));
+                }
+            }
+        }
+    }
+
+    return dependencies;
+}
+
 class QObjectPointerBinding: public QQmlNonbindingBinding
 {
     QQmlMetaObject targetMetaObject;