Add QPolygon::intersects() methods

Corresponds to the similar function QPainterPath::intersects() and is
faster than calculating the intersection and then checking if it is
empty.

Change-Id: I694bb2206ed330a456a41d4118a952a68177b7a2
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>

2 files changed, 47 insertions, 0 deletions

diff --git a/src/gui/painting/qpolygon.cpp b/src/gui/painting/qpolygon.cpp
index 126b752811..3bf6004fcc 100644
--- a/src/gui/painting/qpolygon.cpp
+++ b/src/gui/painting/qpolygon.cpp
@@ -909,6 +909,8 @@ QPolygon QPolygon::united(const QPolygon &r) const
 
     Set operations on polygons will treat the polygons as
     areas. Non-closed polygons will be treated as implicitly closed.
+
+    \sa intersects()
 */
 
 QPolygon QPolygon::intersected(const QPolygon &r) const
@@ -938,6 +940,26 @@ QPolygon QPolygon::subtracted(const QPolygon &r) const
 }
 
 /*!
+    \since 5.10
+
+    Returns \c true if the current polygon intersects at any point the given polygon \a p.
+    Also returns \c true if the current polygon contains or is contained by any part of \a p.
+
+    Set operations on polygons will treat the polygons as
+    areas. Non-closed polygons will be treated as implicitly closed.
+
+    \sa intersected()
+*/
+
+bool QPolygon::intersects(const QPolygon &p) const
+{
+    QPainterPath subject; subject.addPolygon(*this);
+    QPainterPath clip; clip.addPolygon(p);
+
+    return subject.intersects(clip);
+}
+
+/*!
     \since 4.3
 
     Returns a polygon which is the union of this polygon and \a r.
@@ -964,6 +986,7 @@ QPolygonF QPolygonF::united(const QPolygonF &r) const
     Set operations on polygons will treat the polygons as
     areas. Non-closed polygons will be treated as implicitly closed.
 
+    \sa intersects()
 */
 
 QPolygonF QPolygonF::intersected(const QPolygonF &r) const
@@ -992,6 +1015,26 @@ QPolygonF QPolygonF::subtracted(const QPolygonF &r) const
 }
 
 /*!
+    \since 5.10
+
+    Returns \c true if the current polygon intersects at any point the given polygon \a p.
+    Also returns \c true if the current polygon contains or is contained by any part of \a p.
+
+    Set operations on polygons will treat the polygons as
+    areas. Non-closed polygons will be treated as implicitly closed.
+
+    \sa intersected()
+*/
+
+bool QPolygonF::intersects(const QPolygonF &p) const
+{
+    QPainterPath subject; subject.addPolygon(*this);
+    QPainterPath clip; clip.addPolygon(p);
+
+    return subject.intersects(clip);
+}
+
+/*!
    Returns the polygon as a QVariant.
 */
 
diff --git a/src/gui/painting/qpolygon.h b/src/gui/painting/qpolygon.h
index f192e8d10b..8e74a499fd 100644
--- a/src/gui/painting/qpolygon.h
+++ b/src/gui/painting/qpolygon.h
@@ -98,6 +98,8 @@ public:
     Q_REQUIRED_RESULT QPolygon united(const QPolygon &r) const;
     Q_REQUIRED_RESULT QPolygon intersected(const QPolygon &r) const;
     Q_REQUIRED_RESULT QPolygon subtracted(const QPolygon &r) const;
+
+    bool intersects(const QPolygon &r) const;
 };
 Q_DECLARE_SHARED_NOT_MOVABLE_UNTIL_QT6(QPolygon)
 
@@ -175,6 +177,8 @@ public:
     Q_REQUIRED_RESULT QPolygonF united(const QPolygonF &r) const;
     Q_REQUIRED_RESULT QPolygonF intersected(const QPolygonF &r) const;
     Q_REQUIRED_RESULT QPolygonF subtracted(const QPolygonF &r) const;
+
+    bool intersects(const QPolygonF &r) const;
 };
 Q_DECLARE_SHARED_NOT_MOVABLE_UNTIL_QT6(QPolygonF)