Fix QGraphicsView::mapToScene(QRect) to avoid extra adjustments.

The QGraphicsView::mapToScene(QRect) function assumes that QRect and
QRectF share semantics for ::bottomRight(). However, since QRect follows
Qt 3 semantics (the rect is based on viewport pixels and (0,0,1,1) is
equivalent to one pixel, topleft = bottomright), this function gives
unexpected behavior: map(0,0,1,1) gives you an empty polygon! To work
around this, users of the function need to adjust their rectangles
with (0,0,1,1) to get the correct behavior, matching what QRectF does.

QRectF(0,0,1,1).bottomRight() == QPointF(1,1)
QRect(0,0,1,1).bottomRight() == QPoint(0,0)

Reviewed-by: TrustMe

1 files changed, 8 insertions, 7 deletions

diff --git a/src/gui/graphicsview/qgraphicsview.cpp b/src/gui/graphicsview/qgraphicsview.cpp
index bffbf4d..a9d585c 100644
--- a/src/gui/graphicsview/qgraphicsview.cpp
+++ b/src/gui/graphicsview/qgraphicsview.cpp
@@ -1075,7 +1075,7 @@ QList<QGraphicsItem *> QGraphicsViewPrivate::findItems(const QRegion &exposedReg
 
     // Step 1) If all items are contained within the expose region, then
     // return a list of all visible items.
-    const QRectF exposedRegionSceneBounds = q->mapToScene(exposedRegion.boundingRect().adjusted(-1, -1, 2, 2))
+    const QRectF exposedRegionSceneBounds = q->mapToScene(exposedRegion.boundingRect().adjusted(-1, -1, 1, 1))
                                             .boundingRect();
     if (exposedRegionSceneBounds.contains(scene->d_func()->growingItemsBoundingRect)) {
         Q_ASSERT(allItems);
@@ -2313,7 +2313,7 @@ QList<QGraphicsItem *> QGraphicsView::items(const QPoint &pos) const
             QTransform xinv = viewportTransform().inverted();
             return d->scene->items(xinv.mapRect(QRectF(pos.x(), pos.y(), 1, 1)));
         }
-        return d->scene->items(mapToScene(pos.x(), pos.y(), 2, 2));
+        return d->scene->items(mapToScene(pos.x(), pos.y(), 1, 1));
     }
 
     QPainterPath path;
@@ -2475,10 +2475,11 @@ QPolygonF QGraphicsView::mapToScene(const QRect &rect) const
         return QPolygonF();
 
     QPointF scrollOffset(d->horizontalScroll(), d->verticalScroll());
-    QPointF tl = scrollOffset + rect.topLeft();
-    QPointF tr = scrollOffset + rect.topRight();
-    QPointF br = scrollOffset + rect.bottomRight();
-    QPointF bl = scrollOffset + rect.bottomLeft();
+    QRect r = rect.adjusted(0, 0, 1, 1);
+    QPointF tl = scrollOffset + r.topLeft();
+    QPointF tr = scrollOffset + r.topRight();
+    QPointF br = scrollOffset + r.bottomRight();
+    QPointF bl = scrollOffset + r.bottomLeft();
 
     QPolygonF poly;
     poly.resize(4);
@@ -3471,7 +3472,7 @@ void QGraphicsView::paintEvent(QPaintEvent *event)
         exposedRegion = viewport()->rect();
     else if (d->viewportUpdateMode == BoundingRectViewportUpdate)
         exposedRegion = event->rect();
-    QRectF exposedSceneRect = mapToScene(exposedRegion.boundingRect().adjusted(0, 0, 1, 1)).boundingRect();
+    QRectF exposedSceneRect = mapToScene(exposedRegion.boundingRect()).boundingRect();
 
     // Set up the painter
     QPainter painter(viewport());