Add optimized path for QML ShapePath

Improve performance of QML ShapePath, especially with more complex
animating paths. Testing revealed that considerable amount of time
is used for calculating QPainterPath::length(). QML ShapePath
doesn't support QQuickPathAttribute or QQuickPathPercent, so it
can have a fast-path for creating the path without calculating
length or attributes.

This gave heavy bezier lines rendering test ~7x performance boost.

Task-number: QTBUG-64951
Change-Id: I5240ed3516b5eafb0391790ac96835e70f88e540
Reviewed-by: Robin Burchell <robin.burchell@crimson.no>
Reviewed-by: Michael Brasser <michael.brasser@live.com>
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

3 files changed, 45 insertions, 2 deletions

diff --git a/src/quick/util/qquickpath.cpp b/src/quick/util/qquickpath.cpp
index 0323dc9286..1ae9b78669 100644
--- a/src/quick/util/qquickpath.cpp
+++ b/src/quick/util/qquickpath.cpp
@@ -397,7 +397,12 @@ void QQuickPath::processPath()
     d->_pointCache.clear();
     d->prevBez.isValid = false;
 
-    d->_path = createPath(QPointF(), QPointF(), d->_attributes, d->pathLength, d->_attributePoints, &d->closed);
+    if (d->isShapePath) {
+        // This path is a ShapePath, so avoid extra overhead
+        d->_path = createShapePath(QPointF(), QPointF(), d->pathLength, &d->closed);
+    } else {
+        d->_path = createPath(QPointF(), QPointF(), d->_attributes, d->pathLength, d->_attributePoints, &d->closed);
+    }
 
     emit changed();
 }
@@ -493,6 +498,42 @@ QPainterPath QQuickPath::createPath(const QPointF &startPoint, const QPointF &en
     return path;
 }
 
+QPainterPath QQuickPath::createShapePath(const QPointF &startPoint, const QPointF &endPoint, qreal &pathLength, bool *closed)
+{
+    Q_D(QQuickPath);
+
+    if (!d->componentComplete)
+        return QPainterPath();
+
+    QPainterPath path;
+
+    qreal startX = d->startX.isValid() ? d->startX.value : startPoint.x();
+    qreal startY = d->startY.isValid() ? d->startY.value : startPoint.y();
+    path.moveTo(startX, startY);
+
+    int index = 0;
+    for (QQuickCurve *curve : qAsConst(d->_pathCurves)) {
+        QQuickPathData data;
+        data.index = index;
+        data.endPoint = endPoint;
+        data.curves = d->_pathCurves;
+        curve->addToPath(path, data);
+        ++index;
+    }
+
+    if (closed) {
+        QPointF end = path.currentPosition();
+        *closed = startX == end.x() && startY == end.y();
+    }
+
+    // Note: Length of paths inside ShapePath is not used, so currently
+    // length is always 0. This avoids potentially heavy path.length()
+    //pathLength = path.length();
+    pathLength = 0;
+
+    return path;
+}
+
 void QQuickPath::classBegin()
 {
     Q_D(QQuickPath);
diff --git a/src/quick/util/qquickpath_p.h b/src/quick/util/qquickpath_p.h
index d5474e2d30..a49403fd0e 100644
--- a/src/quick/util/qquickpath_p.h
+++ b/src/quick/util/qquickpath_p.h
@@ -522,6 +522,7 @@ private:
 
 public:
     QPainterPath createPath(const QPointF &startPoint, const QPointF &endPoint, const QStringList &attributes, qreal &pathLength, QList<AttributePoint> &attributePoints, bool *closed = 0);
+    QPainterPath createShapePath(const QPointF &startPoint, const QPointF &endPoint, qreal &pathLength, bool *closed = 0);
     static QPointF sequentialPointAt(const QPainterPath &path, const qreal &pathLength, const QList<AttributePoint> &attributePoints, QQuickCachedBezier &prevBez, qreal p, qreal *angle = 0);
 };
 
diff --git a/src/quick/util/qquickpath_p_p.h b/src/quick/util/qquickpath_p_p.h
index 8ce85dbf0f..f5c9664223 100644
--- a/src/quick/util/qquickpath_p_p.h
+++ b/src/quick/util/qquickpath_p_p.h
@@ -72,7 +72,7 @@ public:
     static QQuickPathPrivate* get(QQuickPath *path) { return path->d_func(); }
     static const QQuickPathPrivate* get(const QQuickPath *path) { return path->d_func(); }
 
-    QQuickPathPrivate() : pathLength(0), closed(false), componentComplete(true) { }
+    QQuickPathPrivate() : pathLength(0), closed(false), componentComplete(true), isShapePath(false) { }
 
     QPainterPath _path;
     QList<QQuickPathElement*> _pathElements;
@@ -86,6 +86,7 @@ public:
     qreal pathLength;
     bool closed;
     bool componentComplete;
+    bool isShapePath;
 };
 
 QT_END_NAMESPACE