PathMultiline: handle directly-bound QVector<QPolygonF>

The autotest in 811b15bd161d12e5c85e093f9f492a0c4fa278d6 only tested
what happens if the vector of polygons is passed via a QVariant to the
PathMultiline paths property.  But the intention (as documented) was to
literally support an object with Q_PROPERTY(QVector<QPolygonF> paths ...)
and binding that paths property to PathMultiline.paths.  In that case
it appears in QQuickPathMultiline::setPaths() as a QVariant<QJSValue>,
canConvert<QVector<QPolygonF>>() returns false, then
canConvert<QVariantList>() returns true.  Nevertheless each variant
in the QVariantList is a QPolygonF, as expected.  So we need another
check to detect this case.  Also added a test specifically for that.

Fixes: QTBUG-77929
Change-Id: I84d0a45326d5f007b8ba3cc9bb1fbccf0345d812
Reviewed-by: Paolo Angelelli <paolo.angelelli@qt.io>

1 files changed, 13 insertions, 7 deletions

diff --git a/src/quick/util/qquickpath.cpp b/src/quick/util/qquickpath.cpp
index bebe9b2563..61319c388c 100644
--- a/src/quick/util/qquickpath.cpp
+++ b/src/quick/util/qquickpath.cpp
@@ -2566,14 +2566,20 @@ void QQuickPathMultiline::setPaths(const QVariant &paths)
         QVector<QVector<QPointF>> pathsList;
         QVariantList vll = paths.value<QVariantList>();
         for (const QVariant &v : vll) {
-            QVariantList vl = v.value<QVariantList>();
-            QVector<QPointF> l;
-            for (const QVariant &point : vl) {
-                if (point.canConvert<QPointF>())
-                    l.append(point.toPointF());
+            // If we bind a QVector<QPolygonF> property directly, rather than via QVariant,
+            // it will come through as QJSValue that can be converted to QVariantList of QPolygonF.
+            if (v.canConvert<QPolygonF>()) {
+                pathsList.append(v.value<QPolygonF>());
+            } else {
+                QVariantList vl = v.value<QVariantList>();
+                QVector<QPointF> l;
+                for (const QVariant &point : vl) {
+                    if (point.canConvert<QPointF>())
+                        l.append(point.toPointF());
+                }
+                if (l.size() >= 2)
+                    pathsList.append(l);
             }
-            if (l.size() >= 2)
-                pathsList.append(l);
         }
         setPaths(pathsList);
     } else {