QPointerUniqueId: make fit for release

- Declare as Q_MOVABLE_TYPE
- Prevent QList<QPointerUniqueId> from being instantiated
  (use QVector instead)
- Add equality relational operators
- Add qHash() overload
- Replace non-default ctor with named ctor.
- Add Q_DECL_NOTHROW.
- Add Q_DECL_CONSTEXPR.
- Rename numeric() -> numericId().
- Update docs.

The extension vector for this class calls for additional
properties to be added later, but these are not user-
settable. It thus suffices to rely on the only data
member, a qint64, which can be reinterpreted to an index
into an array or hash with actual objects. This allows
to make the class a Trivial Type (ie. no overhead over
an int) while still supporting later extension. Cf.
QSslEllipticCurve as another example of such a class.

The extension has to maintain the following invariants,
encoded into user code by way of being used in inline
functions:

- m_numericId == -1 <=> !isValid()

This is trivial to support. An extension could not and
still cannot reinterpret the qint64 member as a d-pointer,
but a d-pointer is only necessary for user-settable
properties where updating a central private data structure
would cause too much contention.

Add a test.

Since this type is used in other modules, keep the existing
functions, but mark them as deprecated with the expectation
that these compat functions be removed before 5.8.0 final.

Task-number: QTBUG-54616
Change-Id: Ia3ede0ecaeeef4cd3ffa94a72b1050bd409713a5
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

1 files changed, 30 insertions, 6 deletions

diff --git a/src/gui/kernel/qevent.h b/src/gui/kernel/qevent.h
index a062331bd8..b7c0f3338e 100644
--- a/src/gui/kernel/qevent.h
+++ b/src/gui/kernel/qevent.h
@@ -793,21 +793,45 @@ inline bool operator==(QKeyEvent *e, QKeySequence::StandardKey key){return (e ?
 inline bool operator==(QKeySequence::StandardKey key, QKeyEvent *e){return (e ? e->matches(key) : false);}
 #endif // QT_NO_SHORTCUT
 
-class QPointerUniqueIdPrivate;
 class Q_GUI_EXPORT QPointerUniqueId
 {
     Q_GADGET
-    Q_PROPERTY(qint64 numeric READ numeric CONSTANT)
+    // ### kept these to keep other modules compiling. Remove before 5.8.0 final!
+#if QT_DEPRECATED_SINCE(5, 8)
+    Q_PROPERTY(qint64 numeric READ numericId CONSTANT)
+#endif
+    Q_PROPERTY(qint64 numericId READ numericId CONSTANT)
 public:
-    explicit QPointerUniqueId(qint64 id = -1);
+    Q_ALWAYS_INLINE
+    Q_DECL_CONSTEXPR QPointerUniqueId() Q_DECL_NOTHROW : m_numericId(-1) {}
+    // compiler-generated copy/move ctor/assignment operators are ok!
+    // compiler-generated dtor is ok!
+
+    static QPointerUniqueId fromNumericId(qint64 id);
 
-    qint64 numeric() const;
+    Q_ALWAYS_INLINE Q_DECL_CONSTEXPR bool isValid() const Q_DECL_NOTHROW { return m_numericId != -1; }
+    qint64 numericId() const Q_DECL_NOTHROW;
 
+    // ### kept these to keep other modules compiling. Remove before 5.8.0 final!
+#if QT_DEPRECATED_SINCE(5, 8)
+    Q_ALWAYS_INLINE Q_DECL_DEPRECATED qint64 numeric() const { return numericId(); }
+    Q_ALWAYS_INLINE Q_DECL_DEPRECATED explicit QPointerUniqueId(qint64 id) : m_numericId(id) {}
+#endif
 private:
-    // TODO for TUIO 2, or any other type of complex token ID, a d-pointer can replace
-    // m_numericId without changing the size of this class.
+    // TODO: for TUIO 2, or any other type of complex token ID, an internal
+    // array (or hash) can be added to hold additional properties.
+    // In this case, m_numericId will then turn into an index into that array (or hash).
     qint64 m_numericId;
 };
+Q_DECLARE_TYPEINFO(QPointerUniqueId, Q_MOVABLE_TYPE);
+template <> class QList<QPointerUniqueId> {}; // to prevent instantiation: use QVector instead
+
+Q_GUI_EXPORT bool operator==(QPointerUniqueId lhs, QPointerUniqueId rhs) Q_DECL_NOTHROW;
+inline bool operator!=(QPointerUniqueId lhs, QPointerUniqueId rhs) Q_DECL_NOTHROW
+{ return !operator==(lhs, rhs); }
+Q_GUI_EXPORT uint qHash(QPointerUniqueId key, uint seed = 0) Q_DECL_NOTHROW;
+
+
 
 class QTouchEventTouchPointPrivate;
 class Q_GUI_EXPORT QTouchEvent : public QInputEvent