QPainterPath: Fix boundingRect and controlPointRect ignoring start point

The boundingRect and controlPointRect did not use the start point from
the `QPainterPath(const QPointF &startPoint)` constructor until the
`dirtyBounds` or `dirtyControlBounds` member variables were set to true.
Those two are false on construction. This bug was fixed by adding a new
constructor for QPainterPathPrivate that initializes the `elements`,
`bounds` and `controlBounds` member variables with the start point from
the constructor.

There is also an autotest to verify that the top left of the
boundingRect and controlPointRect are at the same position as
elementAt(0) when the start point constructor is used.

[ChangeLog][QtGui][QPainterPath] boundingRect() and controlPointRect()
now use the start point from QPainterPath(const QPointF &startPoint).

Pick-to: 6.7 6.6 6.5
Change-Id: I7bf30364406c14ed60f75d24b78a9a5535f75d93
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

2 files changed, 16 insertions, 3 deletions

diff --git a/src/gui/painting/qpainterpath.cpp b/src/gui/painting/qpainterpath.cpp
index b57bb0b13b..536318b3a8 100644
--- a/src/gui/painting/qpainterpath.cpp
+++ b/src/gui/painting/qpainterpath.cpp
@@ -517,10 +517,8 @@ QPainterPath::QPainterPath(const QPainterPath &other) = default;
 */
 
 QPainterPath::QPainterPath(const QPointF &startPoint)
-    : d_ptr(new QPainterPathPrivate)
+    : d_ptr(new QPainterPathPrivate(startPoint))
 {
-    Element e = { startPoint.x(), startPoint.y(), MoveToElement };
-    d_func()->elements << e;
 }
 
 void QPainterPath::detach()
diff --git a/src/gui/painting/qpainterpath_p.h b/src/gui/painting/qpainterpath_p.h
index 55164bc347..a07b6cca37 100644
--- a/src/gui/painting/qpainterpath_p.h
+++ b/src/gui/painting/qpainterpath_p.h
@@ -119,6 +119,21 @@ public:
     {
     }
 
+    QPainterPathPrivate(QPointF startPoint)
+        : QSharedData(),
+          elements{ { startPoint.x(), startPoint.y(), QPainterPath::MoveToElement } },
+          cStart(0),
+          fillRule(Qt::OddEvenFill),
+          bounds(startPoint, QSizeF(0, 0)),
+          controlBounds(startPoint, QSizeF(0, 0)),
+          require_moveTo(false),
+          dirtyBounds(false),
+          dirtyControlBounds(false),
+          convex(false),
+          pathConverter(nullptr)
+    {
+    }
+
     QPainterPathPrivate(const QPainterPathPrivate &other) noexcept
         : QSharedData(other),
           elements(other.elements),