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, 9 insertions, 0 deletions

diff --git a/src/qml/qml/qqmlbinding_p.h b/src/qml/qml/qqmlbinding_p.h
index 1c894148e4..38d59a8919 100644
--- a/src/qml/qml/qqmlbinding_p.h
+++ b/src/qml/qml/qqmlbinding_p.h
@@ -102,6 +102,15 @@ public:
     QString expressionIdentifier() const override;
     void expressionChanged() override;
 
+    /**
+     * This method returns a snapshot of the currently tracked dependencies of
+     * this binding. The dependencies can change upon reevaluation. This method is
+     * used in GammaRay to visualize binding hierarchies.
+     *
+     * Call this method from the UI thread.
+     */
+    QVector<QQmlProperty> dependencies() const;
+
 protected:
     virtual void doUpdate(const DeleteWatcher &watcher,
                           QQmlPropertyData::WriteFlags flags, QV4::Scope &scope) = 0;