Gui: mark types Q_PRIMITIVE_TYPE when they're held in QDataBuffer

QDataBuffer assumes that its template argument is a POD, iow: it's ok
to not run ctors and dtors and assign a value into uninitialized
memory.

In Qt, we call that Q_PRIMITIVE_TYPE. Asserting that the QDataBuffer
value_type is not QTypeInfo::isComplex, however, has shown that a
large number of types had not been marked as such, sometimes for good
reason, e.g. because their default constructor doesn't
value-initialize all members, but sets some of them to -1.

Since QDataBuffer doesn't memset the memory to zero, it doesn't
matter, as the code obviously has to have worked before, with
uninitialized memory, and all-zeros is just a special, if common, form
of uninitialized memory.

I also tried to assert is_pod in QDataBuffer (working around the fact
that that particular trait is deprecated), but found that almost none
of the types in question were, in fact, trivial. We should fix this,
because it means the compiler is generating code that's less efficient
than it could be, but that's for another patch.

All types marked as Q_PRIMITIVE_TYPE in this patch are private API, so
this doesn't affect users.

For PathSimplifier::Event, had to shorten the unnamed namespace to not
include the member functions, because Q_DECLARE_TYPEINFO cannot appear
in a namespace other than the Qt one.

Pick-to: 6.4 6.3
Change-Id: I4431a2f269ec1ac4804a87ea71f983eaa34ef867
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
Reviewed-by: Lars Knoll <lars.knoll@gmail.com>

3 files changed, 12 insertions, 3 deletions

diff --git a/src/gui/painting/qpathclipper.cpp b/src/gui/painting/qpathclipper.cpp
index e0b4e5152c..7ada65ce03 100644
--- a/src/gui/painting/qpathclipper.cpp
+++ b/src/gui/painting/qpathclipper.cpp
@@ -63,6 +63,7 @@ struct QIntersection
 
     QPointF pos;
 };
+Q_DECLARE_TYPEINFO(QIntersection, Q_PRIMITIVE_TYPE);
 
 class QIntersectionFinder
 {
diff --git a/src/gui/painting/qpathclipper_p.h b/src/gui/painting/qpathclipper_p.h
index b6cb65630f..f13b96e0ef 100644
--- a/src/gui/painting/qpathclipper_p.h
+++ b/src/gui/painting/qpathclipper_p.h
@@ -79,6 +79,7 @@ public:
     qreal x;
     qreal y;
 };
+Q_DECLARE_TYPEINFO(QPathVertex, Q_PRIMITIVE_TYPE);
 
 class QPathEdge
 {
@@ -122,6 +123,7 @@ public:
 private:
     int m_next[2][2] = { { -1, -1 }, { -1, -1 } };
 };
+Q_DECLARE_TYPEINFO(QPathEdge, Q_PRIMITIVE_TYPE);
 
 class QPathSegments
 {
@@ -135,6 +137,7 @@ public:
             return t < o.t;
         }
     };
+    friend class QTypeInfo<Intersection>;
 
     struct Segment {
         Segment(int pathId, int vertexA, int vertexB)
@@ -156,6 +159,7 @@ public:
 
         QRectF bounds;
     };
+    friend class QTypeInfo<Segment>;
 
 
     QPathSegments(int reserve);
@@ -187,6 +191,8 @@ private:
 
     int m_pathId;
 };
+Q_DECLARE_TYPEINFO(QPathSegments::Intersection, Q_PRIMITIVE_TYPE);
+Q_DECLARE_TYPEINFO(QPathSegments::Segment, Q_PRIMITIVE_TYPE);
 
 class Q_AUTOTEST_EXPORT QWingedEdge
 {
diff --git a/src/gui/painting/qpathsimplifier.cpp b/src/gui/painting/qpathsimplifier.cpp
index af702435c5..6c061b2bb1 100644
--- a/src/gui/painting/qpathsimplifier.cpp
+++ b/src/gui/painting/qpathsimplifier.cpp
@@ -303,6 +303,7 @@ private:
         Type type;
         Element *element;
     };
+    friend class QTypeInfo<Event>;
 
     typedef QRBTree<Element *>::Node RBNode;
     typedef BoundingVolumeHierarchy::Node BVHNode;
@@ -341,6 +342,10 @@ private:
     uint m_hints;
 };
 
+} // unnamed namespace
+
+Q_DECLARE_TYPEINFO(PathSimplifier::Event, Q_PRIMITIVE_TYPE);
+
 inline PathSimplifier::BoundingVolumeHierarchy::BoundingVolumeHierarchy()
     : root(nullptr)
     , nodeBlock(nullptr)
@@ -1614,9 +1619,6 @@ void PathSimplifier::sortEvents(Event *events, int count)
     }
 }
 
-} // end anonymous namespace
-
-
 void qSimplifyPath(const QVectorPath &path, QDataBuffer<QPoint> &vertices,
                    QDataBuffer<quint32> &indices, const QTransform &matrix)
 {