Add clear, reserve and capacity methods to QPainterPath

This allows anticipating and reusing internal allocations of
QPainterPathElements instead of using the common `m_myPath = QPainterPath{}` pattern.

[ChangeLog][QtGui][QPainterPath] Added clear(), reserve(), capacity().
clear() removes allocated QPainterPath elements but preserves allocated memory, which can be
useful for application with complex paths that are often recreated. reserve() and capacity()
follow QVector semantics.

Change-Id: I763461e2a421feda9053d3eb512af2fcf07ade2b
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>

1 files changed, 20 insertions, 0 deletions

diff --git a/src/gui/painting/qpainterpath_p.h b/src/gui/painting/qpainterpath_p.h
index aab318bcab..a36c8005bc 100644
--- a/src/gui/painting/qpainterpath_p.h
+++ b/src/gui/painting/qpainterpath_p.h
@@ -194,6 +194,7 @@ public:
     inline bool isClosed() const;
     inline void close();
     inline void maybeMoveTo();
+    inline void clear();
 
     const QVectorPath &vectorPath() {
         if (!pathConverter)
@@ -290,6 +291,25 @@ inline void QPainterPathData::maybeMoveTo()
     }
 }
 
+inline void QPainterPathData::clear()
+{
+    Q_ASSERT(ref.load() == 1);
+
+    elements.clear();
+
+    cStart = 0;
+
+    bounds = {};
+    controlBounds = {};
+
+    require_moveTo = false;
+    dirtyBounds = false;
+    dirtyControlBounds = false;
+    convex = false;
+
+    delete pathConverter;
+    pathConverter = nullptr;
+}
 #define KAPPA qreal(0.5522847498)