Encapsulate QQmlContextData

This class is not a private detail of QQmlContext. And it is incredibly
hard to see who owns what in there. Let's add some civilization ...

We enforce refcounting for QQmlContextData across the code base, with
two exceptions:

1. QQmlContextPrivate may or may not own its QQmlContextData.
2. We may request a QQmlContextData owned by its parent QQmlContextData.

For these two cases we keep flags in QQmlContextData and when the
respective field (m_parent or m_publicContext) is reset, we release()
once.

Furthermore, QQmlContextData and QQmlGuardedContextData are moved to
their own files, in order to de-spaghettify qqmlcontext_p.h and
qqmlcontext.cpp.

When the QQmlEngine is deleted, any QQmlComponents drop their object
creators now, in order to release any context data held by those.
Before, the context data would be deleted, but the object creators would
retain the dangling pointer.

[ChangeLog][QML][Important Behavior Changes] QQmlContext::baseUrl() does
what the documentation says now: It prefers explicitly set baseUrls over
compilation unit URLs. Only if no baseUrl is set, the CU's URL is
returned. It used to prefer the CU's URL.

Change-Id: Ieeb5dcb07b45d891526191321386d5443b8f5738
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

1 files changed, 19 insertions, 10 deletions

diff --git a/src/qml/qml/qqmlcomponentattached_p.h b/src/qml/qml/qqmlcomponentattached_p.h
index eb6d35652b..b94d474d1f 100644
--- a/src/qml/qml/qqmlcomponentattached_p.h
+++ b/src/qml/qml/qqmlcomponentattached_p.h
@@ -71,24 +71,33 @@ public:
     QQmlComponentAttached(QObject *parent = nullptr);
     ~QQmlComponentAttached();
 
-    void add(QQmlComponentAttached **a) {
-        prev = a; next = *a; *a = this;
-        if (next) next->prev = &next;
+    void insertIntoList(QQmlComponentAttached **listHead)
+    {
+        m_prev = listHead;
+        m_next = *listHead;
+        *listHead = this;
+        if (m_next)
+            m_next->m_prev = &m_next;
     }
-    void rem() {
-        if (next) next->prev = prev;
-        *prev = next;
-        next = nullptr; prev = nullptr;
+
+    void removeFromList()
+    {
+        *m_prev = m_next;
+        if (m_next)
+            m_next->m_prev = m_prev;
+        m_next = nullptr;
+        m_prev = nullptr;
     }
-    QQmlComponentAttached **prev;
-    QQmlComponentAttached *next;
+
+    QQmlComponentAttached *next() const { return m_next; }
 
 Q_SIGNALS:
     void completed();
     void destruction();
 
 private:
-    friend class QQmlContextData;
+    QQmlComponentAttached **m_prev;
+    QQmlComponentAttached *m_next;
 };
 
 QT_END_NAMESPACE