Adds convenience functions QGraphicsItemPrivate::isOpacityNull

This should unify the error constant used along the code and enforce qreal
to avoid unnecessary double conversions.

Reviewed-by: bnilsen
(cherry picked from commit 519760c4256997f26c039cb4b047c6207470b54f)

3 files changed, 14 insertions, 7 deletions

diff --git a/src/gui/graphicsview/qgraphicsitem_p.h b/src/gui/graphicsview/qgraphicsitem_p.h
index 07931dc..5e28d9b 100644
--- a/src/gui/graphicsview/qgraphicsitem_p.h
+++ b/src/gui/graphicsview/qgraphicsitem_p.h
@@ -358,14 +358,20 @@ public:
         return o;
     }
 
+    inline bool isOpacityNull() const
+    { return (opacity < qreal(0.001)); }
+
+    static inline bool isOpacityNull(qreal opacity)
+    { return (opacity < qreal(0.001)); }
+
     inline bool isFullyTransparent() const
     {
-        if (opacity < 0.001)
+        if (isOpacityNull())
             return true;
         if (!parent)
             return false;
 
-        return calcEffectiveOpacity() < 0.001;
+        return isOpacityNull(calcEffectiveOpacity());
     }
 
     inline qreal effectiveOpacity() const {
diff --git a/src/gui/graphicsview/qgraphicsscene.cpp b/src/gui/graphicsview/qgraphicsscene.cpp
index 99f576f..38c2ab8 100644
--- a/src/gui/graphicsview/qgraphicsscene.cpp
+++ b/src/gui/graphicsview/qgraphicsscene.cpp
@@ -4635,7 +4635,7 @@ void QGraphicsScenePrivate::drawSubtreeRecursive(QGraphicsItem *item, QPainter *
         return; // Item has neither contents nor children!(?)
 
     const qreal opacity = item->d_ptr->combineOpacityFromParent(parentOpacity);
-    const bool itemIsFullyTransparent = (opacity < 0.0001);
+    const bool itemIsFullyTransparent = QGraphicsItemPrivate::isOpacityNull(opacity);
     if (itemIsFullyTransparent && (!itemHasChildren || item->d_ptr->childrenCombineOpacity()))
         return;
 
@@ -4755,7 +4755,7 @@ void QGraphicsScenePrivate::draw(QGraphicsItem *item, QPainter *painter, const Q
                                  qreal opacity, const QTransform *effectTransform,
                                  bool wasDirtyParentSceneTransform, bool drawItem)
 {
-    const bool itemIsFullyTransparent = (opacity < 0.0001);
+    const bool itemIsFullyTransparent = QGraphicsItemPrivate::isOpacityNull(opacity);
     const bool itemClipsChildrenToShape = (item->d_ptr->flags & QGraphicsItem::ItemClipsChildrenToShape);
     const bool itemHasChildren = !item->d_ptr->children.isEmpty();
 
@@ -4994,7 +4994,8 @@ void QGraphicsScenePrivate::processDirtyItemsRecursive(QGraphicsItem *item, bool
     }
 
     const qreal opacity = item->d_ptr->combineOpacityFromParent(parentOpacity);
-    const bool itemIsFullyTransparent = !item->d_ptr->ignoreOpacity && opacity < 0.0001;
+    const bool itemIsFullyTransparent = !item->d_ptr->ignoreOpacity
+                                        && QGraphicsItemPrivate::isOpacityNull(opacity);
     if (itemIsFullyTransparent && (!itemHasChildren || item->d_ptr->childrenCombineOpacity())) {
         resetDirtyItem(item, /*recursive=*/itemHasChildren);
         return;
diff --git a/src/gui/graphicsview/qgraphicssceneindex.cpp b/src/gui/graphicsview/qgraphicssceneindex.cpp
index 1fee9dd..3fe3a49 100644
--- a/src/gui/graphicsview/qgraphicssceneindex.cpp
+++ b/src/gui/graphicsview/qgraphicssceneindex.cpp
@@ -279,7 +279,7 @@ void QGraphicsSceneIndexPrivate::recursive_items_helper(QGraphicsItem *item, QRe
         return;
 
     const qreal opacity = item->d_ptr->combineOpacityFromParent(parentOpacity);
-    const bool itemIsFullyTransparent = (opacity < 0.0001);
+    const bool itemIsFullyTransparent = QGraphicsItemPrivate::isOpacityNull(opacity);
     const bool itemHasChildren = !item->d_ptr->children.isEmpty();
     if (itemIsFullyTransparent && (!itemHasChildren || item->d_ptr->childrenCombineOpacity()))
         return;
@@ -554,7 +554,7 @@ QList<QGraphicsItem *> QGraphicsSceneIndex::estimateTopLevelItems(const QRectF &
 
 /*!
     \fn QList<QGraphicsItem *> QGraphicsSceneIndex::items(Qt::SortOrder order = Qt::DescendingOrder) const
-    
+
     This pure virtual function all items in the index and sort them using
     \a order.
 */