Fixes bug when using AnchorUnderMouse for GraphicsView transformation.

We now automatically enable mouse tracking on the viewport of the
GraphicsView when setting AnchorUnderMouse as transformationAnchor or
resizeAnchor.

Autotest included.

Task-number: QTBUG-6835
Reviewed-by: bnilsen

1 files changed, 16 insertions, 3 deletions

diff --git a/src/gui/graphicsview/qgraphicsview.cpp b/src/gui/graphicsview/qgraphicsview.cpp
index ffe64aa..3bb40fb 100644
--- a/src/gui/graphicsview/qgraphicsview.cpp
+++ b/src/gui/graphicsview/qgraphicsview.cpp
@@ -1208,6 +1208,11 @@ void QGraphicsView::setTransformationAnchor(ViewportAnchor anchor)
 {
     Q_D(QGraphicsView);
     d->transformationAnchor = anchor;
+
+    // Ensure mouse tracking is enabled in the case we are using AnchorUnderMouse
+    // in order to have up-to-date information for centering the view.
+    if (d->transformationAnchor == AnchorUnderMouse)
+        d->viewport->setMouseTracking(true);
 }
 
 /*!
@@ -1235,6 +1240,11 @@ void QGraphicsView::setResizeAnchor(ViewportAnchor anchor)
 {
     Q_D(QGraphicsView);
     d->resizeAnchor = anchor;
+
+    // Ensure mouse tracking is enabled in the case we are using AnchorUnderMouse
+    // in order to have up-to-date information for centering the view.
+    if (d->resizeAnchor == AnchorUnderMouse)
+        d->viewport->setMouseTracking(true);
 }
 
 /*!
@@ -2597,9 +2607,12 @@ void QGraphicsView::setupViewport(QWidget *widget)
     }
 
     // We are only interested in mouse tracking if items
-    // accept hover events or use non-default cursors.
-    if (d->scene && (!d->scene->d_func()->allItemsIgnoreHoverEvents
-                     || !d->scene->d_func()->allItemsUseDefaultCursor)) {
+    // accept hover events or use non-default cursors or if
+    // AnchorUnderMouse is used as transformation or resize anchor.
+    if ((d->scene && (!d->scene->d_func()->allItemsIgnoreHoverEvents
+                     || !d->scene->d_func()->allItemsUseDefaultCursor))
+        || d->transformationAnchor == AnchorUnderMouse
+        || d->resizeAnchor == AnchorUnderMouse) {
         widget->setMouseTracking(true);
     }