Reduced memory footprint of QGraphicsWidget.

This commit reduces the memory footprint of QGraphicsWidget by
around 40% (from around 663 bytes to around 409 bytes - measured
using /proc/<pid>/statm on Linux - see 'man 5 proc').

The technique used is to lazily allocate (on the heap) certain
data structures (i.e. not allocate them unless they are needed):

  - QGraphicsLayoutItemPrivate::userSizeHints
    => used only if the size, width, or height is explicitly set

  - QGraphicsWidgetPrivate::margins
    => used only if the contents margins are accessed

  - QGraphicsWidgetPrivate::windowFrameMargins
    => used only if the window frame margins are accessed

  - QGraphicsWidgetPrivate::windowData
    => used only if the graphics widget is a window

In addition, a few unused data members (and related code) were removed:

  - QGraphicsWidgetPrivate::contentsRect
  - QGraphicsWidgetPrivate::mouseDelta
  - QGraphicsWidgetPrivate::*LayoutItemMargin

Reviewed-by: andreas
Task-number: 251592

5 files changed, 298 insertions, 259 deletions

diff --git a/src/gui/graphicsview/qgraphicslayoutitem.cpp b/src/gui/graphicsview/qgraphicslayoutitem.cpp
index eaa97ff..e058292 100644
--- a/src/gui/graphicsview/qgraphicslayoutitem.cpp
+++ b/src/gui/graphicsview/qgraphicslayoutitem.cpp
@@ -108,13 +108,22 @@ static void normalizeHints(qreal &minimum, qreal &preferred, qreal &maximum, qre
     \internal
 */
 QGraphicsLayoutItemPrivate::QGraphicsLayoutItemPrivate(QGraphicsLayoutItem *par, bool layout)
-    : parent(par), isLayout(layout), ownedByLayout(false), graphicsItem(0)
+    : parent(par), userSizeHints(0), isLayout(layout), ownedByLayout(false), graphicsItem(0)
 {
 }
 
 /*!
     \internal
 */
+QGraphicsLayoutItemPrivate::~QGraphicsLayoutItemPrivate()
+{
+    // Remove any lazily allocated data
+    delete[] userSizeHints;
+}
+
+/*!
+    \internal
+*/
 void QGraphicsLayoutItemPrivate::init()
 {
     sizeHintCacheDirty = true;
@@ -132,7 +141,8 @@ QSizeF *QGraphicsLayoutItemPrivate::effectiveSizeHints(const QSizeF &constraint)
 
     for (int i = 0; i < Qt::NSizeHints; ++i) {
         cachedSizeHints[i] = constraint;
-        combineSize(cachedSizeHints[i], userSizeHints[i]);
+        if (userSizeHints)
+            combineSize(cachedSizeHints[i], userSizeHints[i]);
     }
 
     QSizeF &minS = cachedSizeHints[Qt::MinimumSize];
@@ -198,6 +208,58 @@ QGraphicsItem *QGraphicsLayoutItemPrivate::parentItem() const
 }
 
 /*!
+    \internal
+
+     Ensures that userSizeHints is allocated.
+     This function must be called before any dereferencing.
+*/
+void QGraphicsLayoutItemPrivate::ensureUserSizeHints()
+{
+    if (!userSizeHints)
+        userSizeHints = new QSizeF[Qt::NSizeHints];
+}
+
+/*!
+    \internal
+
+    Sets the user size hint \a which to \a size. Use an invalid size to unset the size hint.
+ */
+void QGraphicsLayoutItemPrivate::setSize(Qt::SizeHint which, const QSizeF &size)
+{
+    Q_Q(QGraphicsLayoutItem);
+
+    if (userSizeHints) {
+        if (size == userSizeHints[which])
+            return;
+    } else if (!size.isValid()) {
+        return;
+    }
+
+    ensureUserSizeHints();
+    userSizeHints[which] = size;
+    q->updateGeometry();
+}
+
+/*!
+    \internal
+
+    Sets the width of the user size hint \a which to \a width.
+ */
+void QGraphicsLayoutItemPrivate::setSizeComponent(
+    Qt::SizeHint which, SizeComponent component, qreal value)
+{
+    Q_Q(QGraphicsLayoutItem);
+    ensureUserSizeHints();
+    qreal &userValue = (component == Width)
+        ? userSizeHints[which].rwidth()
+        : userSizeHints[which].rheight();
+    if (value == userValue)
+        return;
+    userValue = value;
+    q->updateGeometry();
+}
+
+/*!
     \class QGraphicsLayoutItem
     \brief The QGraphicsLayoutItem class can be inherited to allow your custom
     items to be managed by layouts.
@@ -381,12 +443,7 @@ QSizePolicy QGraphicsLayoutItem::sizePolicy() const
 */
 void QGraphicsLayoutItem::setMinimumSize(const QSizeF &size)
 {
-    Q_D(QGraphicsLayoutItem);
-    if (size == d->userSizeHints[Qt::MinimumSize])
-        return;
-
-    d->userSizeHints[Qt::MinimumSize] = size;
-    updateGeometry();
+    d_ptr->setSize(Qt::MinimumSize, size);
 }
 
 /*!
@@ -416,12 +473,7 @@ QSizeF QGraphicsLayoutItem::minimumSize() const
 */
 void QGraphicsLayoutItem::setMinimumWidth(qreal width)
 {
-    Q_D(QGraphicsLayoutItem);
-    qreal &userSizeHint = d->userSizeHints[Qt::MinimumSize].rwidth();
-    if (width == userSizeHint)
-        return;
-    userSizeHint = width;
-    updateGeometry();
+    d_ptr->setSizeComponent(Qt::MinimumSize, d_ptr->Width, width);
 }
 
 /*!
@@ -431,12 +483,7 @@ void QGraphicsLayoutItem::setMinimumWidth(qreal width)
 */
 void QGraphicsLayoutItem::setMinimumHeight(qreal height)
 {
-    Q_D(QGraphicsLayoutItem);
-    qreal &userSizeHint = d->userSizeHints[Qt::MinimumSize].rheight();
-    if (height == userSizeHint)
-        return;
-    userSizeHint = height;
-    updateGeometry();
+    d_ptr->setSizeComponent(Qt::MinimumSize, d_ptr->Height, height);
 }
 
 
@@ -450,12 +497,7 @@ void QGraphicsLayoutItem::setMinimumHeight(qreal height)
 */
 void QGraphicsLayoutItem::setPreferredSize(const QSizeF &size)
 {
-    Q_D(QGraphicsLayoutItem);
-    if (size == d->userSizeHints[Qt::PreferredSize])
-        return;
-
-    d->userSizeHints[Qt::PreferredSize] = size;
-    updateGeometry();
+    d_ptr->setSize(Qt::PreferredSize, size);
 }
 
 /*!
@@ -485,12 +527,7 @@ QSizeF QGraphicsLayoutItem::preferredSize() const
 */
 void QGraphicsLayoutItem::setPreferredHeight(qreal height)
 {
-    Q_D(QGraphicsLayoutItem);
-    qreal &userSizeHint = d->userSizeHints[Qt::PreferredSize].rheight();
-    if (height == userSizeHint)
-        return;
-    userSizeHint = height;
-    updateGeometry();
+    d_ptr->setSizeComponent(Qt::PreferredSize, d_ptr->Height, height);
 }
 
 /*!
@@ -500,12 +537,7 @@ void QGraphicsLayoutItem::setPreferredHeight(qreal height)
 */
 void QGraphicsLayoutItem::setPreferredWidth(qreal width)
 {
-    Q_D(QGraphicsLayoutItem);
-    qreal &userSizeHint = d->userSizeHints[Qt::PreferredSize].rwidth();
-    if (width == userSizeHint)
-        return;
-    userSizeHint = width;
-    updateGeometry();
+    d_ptr->setSizeComponent(Qt::PreferredSize, d_ptr->Width, width);
 }
 
 /*!
@@ -519,12 +551,7 @@ void QGraphicsLayoutItem::setPreferredWidth(qreal width)
 */
 void QGraphicsLayoutItem::setMaximumSize(const QSizeF &size)
 {
-    Q_D(QGraphicsLayoutItem);
-    if (size == d->userSizeHints[Qt::MaximumSize])
-        return;
-
-    d->userSizeHints[Qt::MaximumSize] = size;
-    updateGeometry();
+    d_ptr->setSize(Qt::MaximumSize, size);
 }
 
 /*!
@@ -554,12 +581,7 @@ QSizeF QGraphicsLayoutItem::maximumSize() const
 */
 void QGraphicsLayoutItem::setMaximumWidth(qreal width)
 {
-    Q_D(QGraphicsLayoutItem);
-    qreal &userSizeHint = d->userSizeHints[Qt::MaximumSize].rwidth();
-    if (width == userSizeHint)
-        return;
-    userSizeHint = width;
-    updateGeometry();
+    d_ptr->setSizeComponent(Qt::MaximumSize, d_ptr->Width, width);
 }
 
 /*!
@@ -569,12 +591,7 @@ void QGraphicsLayoutItem::setMaximumWidth(qreal width)
 */
 void QGraphicsLayoutItem::setMaximumHeight(qreal height)
 {
-    Q_D(QGraphicsLayoutItem);
-    qreal &userSizeHint = d->userSizeHints[Qt::MaximumSize].rheight();
-    if (height == userSizeHint)
-        return;
-    userSizeHint = height;
-    updateGeometry();
+    d_ptr->setSizeComponent(Qt::MaximumSize, d_ptr->Height, height);
 }
 
 /*!
@@ -732,6 +749,11 @@ QRectF QGraphicsLayoutItem::contentsRect() const
 */
 QSizeF QGraphicsLayoutItem::effectiveSizeHint(Qt::SizeHint which, const QSizeF &constraint) const
 {
+    Q_D(const QGraphicsLayoutItem);
+
+    if (!d->userSizeHints && constraint.isValid())
+        return constraint;
+
     // ### should respect size policy???
     return d_ptr->effectiveSizeHints(constraint)[which];
 }
diff --git a/src/gui/graphicsview/qgraphicslayoutitem_p.h b/src/gui/graphicsview/qgraphicslayoutitem_p.h
index fab0f39..dc044e6 100644
--- a/src/gui/graphicsview/qgraphicslayoutitem_p.h
+++ b/src/gui/graphicsview/qgraphicslayoutitem_p.h
@@ -63,16 +63,20 @@ class Q_AUTOTEST_EXPORT QGraphicsLayoutItemPrivate
 {
     Q_DECLARE_PUBLIC(QGraphicsLayoutItem)
 public:
-    virtual ~QGraphicsLayoutItemPrivate() {}
+    virtual ~QGraphicsLayoutItemPrivate();
     QGraphicsLayoutItemPrivate(QGraphicsLayoutItem *parent, bool isLayout);
     void init();
     QSizeF *effectiveSizeHints(const QSizeF &constraint) const;
     QGraphicsItem *parentItem() const;
+    void ensureUserSizeHints();
+    void setSize(Qt::SizeHint which, const QSizeF &size);
+    enum SizeComponent { Width, Height };
+    void setSizeComponent(Qt::SizeHint which, SizeComponent component, qreal value);
 
     QSizePolicy sizePolicy;
     QGraphicsLayoutItem *parent;
 
-    QSizeF userSizeHints[Qt::NSizeHints];
+    QSizeF *userSizeHints;
     mutable QSizeF cachedSizeHints[Qt::NSizeHints];
     mutable QSizeF cachedConstraint;
 
diff --git a/src/gui/graphicsview/qgraphicswidget.cpp b/src/gui/graphicsview/qgraphicswidget.cpp
index 66930f2..702e0b6 100644
--- a/src/gui/graphicsview/qgraphicswidget.cpp
+++ b/src/gui/graphicsview/qgraphicswidget.cpp
@@ -459,17 +459,19 @@ void QGraphicsWidget::setContentsMargins(qreal left, qreal top, qreal right, qre
 {
     Q_D(QGraphicsWidget);
 
-    if (left == d->leftMargin
-        && top == d->topMargin
-        && right == d->rightMargin
-        && bottom == d->bottomMargin) {
+    if (!d->margins && left == 0 && top == 0 && right == 0 && bottom == 0)
+        return;
+    d->ensureMargins();
+    if (left == d->margins[d->Left]
+        && top == d->margins[d->Top]
+        && right == d->margins[d->Right]
+        && bottom == d->margins[d->Bottom])
         return;
-    }
 
-    d->leftMargin = left;
-    d->topMargin = top;
-    d->rightMargin = right;
-    d->bottomMargin = bottom;
+    d->margins[d->Left] = left;
+    d->margins[d->Top] = top;
+    d->margins[d->Right] = right;
+    d->margins[d->Bottom] = bottom;
 
     if (QGraphicsLayout *l = d->layout)
         l->invalidate();
@@ -490,14 +492,16 @@ void QGraphicsWidget::setContentsMargins(qreal left, qreal top, qreal right, qre
 void QGraphicsWidget::getContentsMargins(qreal *left, qreal *top, qreal *right, qreal *bottom) const
 {
     Q_D(const QGraphicsWidget);
+    if (left || top || right || bottom)
+        d->ensureMargins();
     if (left)
-        *left = d->leftMargin;
+        *left = d->margins[d->Left];
     if (top)
-        *top = d->topMargin;
+        *top = d->margins[d->Top];
     if (right)
-        *right = d->rightMargin;
+        *right = d->margins[d->Right];
     if (bottom)
-        *bottom = d->bottomMargin;
+        *bottom = d->margins[d->Bottom];
 }
 
 /*!
@@ -513,16 +517,23 @@ void QGraphicsWidget::getContentsMargins(qreal *left, qreal *top, qreal *right,
 void QGraphicsWidget::setWindowFrameMargins(qreal left, qreal top, qreal right, qreal bottom)
 {
     Q_D(QGraphicsWidget);
-    bool unchanged = left == d->leftWindowFrameMargin && top == d->topWindowFrameMargin
-                     && right == d->rightWindowFrameMargin && bottom == d->bottomWindowFrameMargin;
+
+    if (!d->windowFrameMargins && left == 0 && top == 0 && right == 0 && bottom == 0)
+        return;
+    d->ensureWindowFrameMargins();
+    bool unchanged =
+        d->windowFrameMargins[d->Left] == left
+        && d->windowFrameMargins[d->Top] == top
+        && d->windowFrameMargins[d->Right] == right
+        && d->windowFrameMargins[d->Bottom] == bottom;
     if (d->setWindowFrameMargins && unchanged)
         return;
     if (!unchanged)
         prepareGeometryChange();
-    d->leftWindowFrameMargin = left;
-    d->topWindowFrameMargin = top;
-    d->rightWindowFrameMargin = right;
-    d->bottomWindowFrameMargin = bottom;
+    d->windowFrameMargins[d->Left] = left;
+    d->windowFrameMargins[d->Top] = top;
+    d->windowFrameMargins[d->Right] = right;
+    d->windowFrameMargins[d->Bottom] = bottom;
     d->setWindowFrameMargins = true;
 }
 
@@ -536,14 +547,16 @@ void QGraphicsWidget::setWindowFrameMargins(qreal left, qreal top, qreal right,
 void QGraphicsWidget::getWindowFrameMargins(qreal *left, qreal *top, qreal *right, qreal *bottom) const
 {
     Q_D(const QGraphicsWidget);
+    if (left || top || right || bottom)
+        d->ensureWindowFrameMargins();
     if (left)
-        *left = d->leftWindowFrameMargin;
+        *left = d->windowFrameMargins[d->Left];
     if (top)
-        *top = d->topWindowFrameMargin;
+        *top = d->windowFrameMargins[d->Top];
     if (right)
-        *right = d->rightWindowFrameMargin;
+        *right = d->windowFrameMargins[d->Right];
     if (bottom)
-        *bottom = d->bottomWindowFrameMargin;
+        *bottom = d->windowFrameMargins[d->Bottom];
 }
 
 /*!
@@ -577,8 +590,10 @@ void QGraphicsWidget::unsetWindowFrameMargins()
 QRectF QGraphicsWidget::windowFrameGeometry() const
 {
     Q_D(const QGraphicsWidget);
-    return geometry().adjusted(-d->leftWindowFrameMargin, -d->topWindowFrameMargin,
-                               d->rightWindowFrameMargin, d->bottomWindowFrameMargin);
+    return d->windowFrameMargins
+        ? geometry().adjusted(-d->windowFrameMargins[d->Left], -d->windowFrameMargins[d->Top],
+                              d->windowFrameMargins[d->Right], d->windowFrameMargins[d->Bottom])
+        : geometry();
 }
 
 /*!
@@ -589,8 +604,10 @@ QRectF QGraphicsWidget::windowFrameGeometry() const
 QRectF QGraphicsWidget::windowFrameRect() const
 {
     Q_D(const QGraphicsWidget);
-    return rect().adjusted(-d->leftWindowFrameMargin, -d->topWindowFrameMargin,
-                           d->rightWindowFrameMargin, d->bottomWindowFrameMargin);
+    return d->windowFrameMargins
+        ? rect().adjusted(-d->windowFrameMargins[d->Left], -d->windowFrameMargins[d->Top],
+                          d->windowFrameMargins[d->Right], d->windowFrameMargins[d->Bottom])
+        : rect();
 }
 
 /*!
@@ -699,7 +716,10 @@ QSizeF QGraphicsWidget::sizeHint(Qt::SizeHint which, const QSizeF &constraint) c
     QSizeF sh;
     if (d->layout) {
         sh = d->layout->effectiveSizeHint(which, constraint);
-        sh += QSizeF(d->leftMargin + d->rightMargin, d->topMargin + d->bottomMargin);
+        if (d->margins) {
+            sh += QSizeF(d->margins[d->Left] + d->margins[d->Right],
+                         d->margins[d->Top] + d->margins[d->Bottom]);
+        }
     } else {
         switch (which) {
             case Qt::MinimumSize:
@@ -1127,7 +1147,8 @@ bool QGraphicsWidget::windowFrameEvent(QEvent *event)
         d->windowFrameMousePressEvent(static_cast<QGraphicsSceneMouseEvent *>(event));
         break;
     case QEvent::GraphicsSceneMouseMove:
-        if (d->grabbedSection != Qt::NoSection) {
+        d->ensureWindowData();
+        if (d->windowData->grabbedSection != Qt::NoSection) {
             d->windowFrameMouseMoveEvent(static_cast<QGraphicsSceneMouseEvent *>(event));
             event->accept();
         }
@@ -1182,7 +1203,8 @@ Qt::WindowFrameSection QGraphicsWidget::windowFrameSectionAt(const QPointF &pos)
 
     const qreal cornerMargin = 20;
     //### Not sure of this one, it should be the same value for all edges.
-    const qreal windowFrameWidth = d->leftWindowFrameMargin;
+    const qreal windowFrameWidth = d->windowFrameMargins
+        ? d->windowFrameMargins[d->Left] : 0;
 
     Qt::WindowFrameSection s = Qt::NoSection;
     if (x <= left + cornerMargin) {
@@ -1208,7 +1230,8 @@ Qt::WindowFrameSection QGraphicsWidget::windowFrameSectionAt(const QPointF &pos)
     }
     if (s == Qt::NoSection) {
         QRectF r1 = r;
-        r1.setHeight(d->topWindowFrameMargin);
+        r1.setHeight(d->windowFrameMargins
+                     ? d->windowFrameMargins[d->Top] : 0);
         if (r1.contains(pos))
             s = Qt::TitleBarArea;
     }
@@ -1316,7 +1339,8 @@ bool QGraphicsWidget::event(QEvent *event)
     case QEvent::GraphicsSceneMouseMove:
     case QEvent::GraphicsSceneMouseRelease:
     case QEvent::GraphicsSceneMouseDoubleClick:
-        if (d->hasDecoration() && d->grabbedSection != Qt::NoSection)
+        d->ensureWindowData();
+        if (d->hasDecoration() && d->windowData->grabbedSection != Qt::NoSection)
             return windowFrameEvent(event);
         break;
     case QEvent::GraphicsSceneHoverEnter:
@@ -1669,12 +1693,13 @@ bool QGraphicsWidget::isActiveWindow() const
 void QGraphicsWidget::setWindowTitle(const QString &title)
 {
     Q_D(QGraphicsWidget);
-    d->windowTitle = title;
+    d->ensureWindowData();
+    d->windowData->windowTitle = title;
 }
 QString QGraphicsWidget::windowTitle() const
 {
     Q_D(const QGraphicsWidget);
-    return d->windowTitle;
+    return d->windowData ? d->windowData->windowTitle : QString();
 }
 
 /*!
@@ -2110,11 +2135,12 @@ void QGraphicsWidget::paintWindowFrame(QPainter *painter, const QStyleOptionGrap
     QStyleOptionTitleBar bar;
     bar.QStyleOption::operator=(*option);
     d->initStyleOptionTitleBar(&bar);   // this clear flags in bar.state
-    if (d->buttonMouseOver)
+    d->ensureWindowData();
+    if (d->windowData->buttonMouseOver)
         bar.state |= QStyle::State_MouseOver;
     else
         bar.state &= ~QStyle::State_MouseOver;
-    if (d->buttonSunken)
+    if (d->windowData->buttonSunken)
         bar.state |= QStyle::State_Sunken;
     else
         bar.state &= ~QStyle::State_Sunken;
diff --git a/src/gui/graphicsview/qgraphicswidget_p.cpp b/src/gui/graphicsview/qgraphicswidget_p.cpp
index 4b41a31..8ced47a 100644
--- a/src/gui/graphicsview/qgraphicswidget_p.cpp
+++ b/src/gui/graphicsview/qgraphicswidget_p.cpp
@@ -89,56 +89,57 @@ qreal QGraphicsWidgetPrivate::titleBarHeight(const QStyleOptionTitleBar &options
     return (qreal)height;
 }
 
-void QGraphicsWidgetPrivate::getLayoutItemMargins(qreal *left, qreal *top, qreal *right, qreal *bottom) const
+/*!
+    \internal
+*/
+QGraphicsWidgetPrivate::~QGraphicsWidgetPrivate()
 {
-    if (left)
-        *left = leftLayoutItemMargin;
-    if (top)
-        *top = topLayoutItemMargin;
-    if (right)
-        *right = rightLayoutItemMargin;
-    if (bottom)
-        *bottom = bottomLayoutItemMargin;
+    // Remove any lazily allocated data
+    delete[] margins;
+    delete[] windowFrameMargins;
+    delete windowData;
 }
 
-void QGraphicsWidgetPrivate::setLayoutItemMargins(qreal left, qreal top, qreal right, qreal bottom)
-{
-    if (leftLayoutItemMargin == left
-        && topLayoutItemMargin == top
-        && rightLayoutItemMargin == right
-        && bottomLayoutItemMargin == bottom)
-        return;
+/*!
+    \internal
 
-    Q_Q(QGraphicsWidget);
-    leftLayoutItemMargin = left;
-    topLayoutItemMargin = top;
-    rightLayoutItemMargin = right;
-    bottomLayoutItemMargin = bottom;
-    q->updateGeometry();
+     Ensures that margins is allocated.
+     This function must be called before any dereferencing.
+*/
+void QGraphicsWidgetPrivate::ensureMargins() const
+{
+    if (!margins) {
+        margins = new qreal[4];
+        for (int i = 0; i < 4; ++i)
+            margins[i] = 0;
+    }
 }
 
-void QGraphicsWidgetPrivate::setLayoutItemMargins(QStyle::SubElement element, const QStyleOption *opt)
+/*!
+    \internal
+
+     Ensures that windowFrameMargins is allocated.
+     This function must be called before any dereferencing.
+*/
+void QGraphicsWidgetPrivate::ensureWindowFrameMargins() const
 {
-    Q_Q(QGraphicsWidget);
-    QStyleOption myOpt;
-    if (!opt) {
-        q->initStyleOption(&myOpt);
-        myOpt.rect.setRect(0, 0, 32768, 32768);     // arbitrary
-        opt = &myOpt;
+    if (!windowFrameMargins) {
+        windowFrameMargins = new qreal[4];
+        for (int i = 0; i < 4; ++i)
+            windowFrameMargins[i] = 0;
     }
+}
 
-    QRect liRect = q->style()->subElementRect(element, opt, /* q */ 0);
-    if (liRect.isValid()) {
-        leftLayoutItemMargin = (opt->rect.left() - liRect.left());
-        topLayoutItemMargin = (opt->rect.top() - liRect.top());
-        rightLayoutItemMargin = (liRect.right() - opt->rect.right());
-        bottomLayoutItemMargin = (liRect.bottom() - opt->rect.bottom());
-    } else {
-        leftLayoutItemMargin = 0;
-        topLayoutItemMargin = 0;
-        rightLayoutItemMargin = 0;
-        bottomLayoutItemMargin = 0;
-    }
+/*!
+    \internal
+
+     Ensures that windowData is allocated.
+     This function must be called before any dereferencing.
+*/
+void QGraphicsWidgetPrivate::ensureWindowData()
+{
+    if (!windowData)
+        windowData = new WindowData;
 }
 
 void QGraphicsWidgetPrivate::setPalette_helper(const QPalette &palette)
@@ -297,11 +298,12 @@ QFont QGraphicsWidgetPrivate::naturalWidgetFont() const
 void QGraphicsWidgetPrivate::initStyleOptionTitleBar(QStyleOptionTitleBar *option)
 {
     Q_Q(QGraphicsWidget);
+    ensureWindowData();
     q->initStyleOption(option);
     option->rect.setHeight(titleBarHeight(*option));
     option->titleBarFlags = windowFlags;
     option->subControls = QStyle::SC_TitleBarCloseButton | QStyle::SC_TitleBarLabel | QStyle::SC_TitleBarSysMenu;
-    option->activeSubControls = hoveredSubControl;
+    option->activeSubControls = windowData->hoveredSubControl;
     bool isActive = q->isActiveWindow();
     if (isActive) {
         option->state |= QStyle::State_Active;
@@ -313,7 +315,8 @@ void QGraphicsWidgetPrivate::initStyleOptionTitleBar(QStyleOptionTitleBar *optio
     }
     QFont windowTitleFont = QApplication::font("QWorkspaceTitleBar");
     QRect textRect = q->style()->subControlRect(QStyle::CC_TitleBar, option, QStyle::SC_TitleBarLabel, 0);
-    option->text = QFontMetrics(windowTitleFont).elidedText(windowTitle, Qt::ElideRight, textRect.width());
+    option->text = QFontMetrics(windowTitleFont).elidedText(
+        windowData->windowTitle, Qt::ElideRight, textRect.width());
 }
 
 void QGraphicsWidgetPrivate::adjustWindowFlags(Qt::WindowFlags *flags)
@@ -341,9 +344,10 @@ void QGraphicsWidgetPrivate::adjustWindowFlags(Qt::WindowFlags *flags)
 void QGraphicsWidgetPrivate::windowFrameMouseReleaseEvent(QGraphicsSceneMouseEvent *event)
 {
     Q_Q(QGraphicsWidget);
-    if (grabbedSection != Qt::NoSection) {
-        if (grabbedSection == Qt::TitleBarArea) {
-            buttonSunken = false;
+    ensureWindowData();
+    if (windowData->grabbedSection != Qt::NoSection) {
+        if (windowData->grabbedSection == Qt::TitleBarArea) {
+            windowData->buttonSunken = false;
             QStyleOptionTitleBar bar;
             initStyleOptionTitleBar(&bar);
             // make sure that the coordinates (rect and pos) we send to the style are positive.
@@ -351,8 +355,10 @@ void QGraphicsWidgetPrivate::windowFrameMouseReleaseEvent(QGraphicsSceneMouseEve
             bar.rect.moveTo(0,0);
             bar.rect.setHeight(q->style()->pixelMetric(QStyle::PM_TitleBarHeight, &bar));
             QPointF pos = event->pos();
-            pos.rx() += leftWindowFrameMargin;
-            pos.ry() += topWindowFrameMargin;
+            if (windowFrameMargins) {
+                pos.rx() += windowFrameMargins[Left];
+                pos.ry() += windowFrameMargins[Top];
+            }
             bar.subControls = QStyle::SC_TitleBarCloseButton;
             if (q->style()->subControlRect(QStyle::CC_TitleBar, &bar,
                                            QStyle::SC_TitleBarCloseButton,
@@ -361,7 +367,7 @@ void QGraphicsWidgetPrivate::windowFrameMouseReleaseEvent(QGraphicsSceneMouseEve
             }
         }
         if (!(static_cast<QGraphicsSceneMouseEvent *>(event)->buttons()))
-            grabbedSection = Qt::NoSection;
+            windowData->grabbedSection = Qt::NoSection;
         event->accept();
     }
 }
@@ -372,35 +378,16 @@ void QGraphicsWidgetPrivate::windowFrameMousePressEvent(QGraphicsSceneMouseEvent
     if (event->button() != Qt::LeftButton)
         return;
 
-    startGeometry = q->geometry();
-    grabbedSection = q->windowFrameSectionAt(event->pos());
-    switch (grabbedSection) {
-    case Qt::LeftSection:
-    case Qt::TopLeftSection:
-        mouseDelta = event->pos() - q->rect().topLeft();
-        break;
-    case Qt::TopSection:
-    case Qt::TopRightSection:
-        mouseDelta = event->pos() - q->rect().topRight();
-        break;
-    case Qt::RightSection:
-    case Qt::BottomRightSection:
-        mouseDelta = event->pos() - q->rect().bottomRight();
-        break;
-    case Qt::BottomSection:
-    case Qt::BottomLeftSection:
-        mouseDelta = event->pos() - q->rect().bottomLeft();
-        break;
-    case Qt::TitleBarArea:
-        if (hoveredSubControl == QStyle::SC_TitleBarCloseButton) {
-            buttonSunken = true;
-            q->update();
-        }
-        break;
-    case Qt::NoSection:
-        break;
+    ensureWindowData();
+    windowData->startGeometry = q->geometry();
+    windowData->grabbedSection = q->windowFrameSectionAt(event->pos());
+    ensureWindowData();
+    if (windowData->grabbedSection == Qt::TitleBarArea
+        && windowData->hoveredSubControl == QStyle::SC_TitleBarCloseButton) {
+        windowData->buttonSunken = true;
+        q->update();
     }
-    event->setAccepted(grabbedSection != Qt::NoSection);
+    event->setAccepted(windowData->grabbedSection != Qt::NoSection);
 }
 
 static void _q_boundGeometryToSizeConstraints(const QRectF &startGeometry,
@@ -455,7 +442,8 @@ static void _q_boundGeometryToSizeConstraints(const QRectF &startGeometry,
 void QGraphicsWidgetPrivate::windowFrameMouseMoveEvent(QGraphicsSceneMouseEvent *event)
 {
     Q_Q(QGraphicsWidget);
-    if (!(event->buttons() & Qt::LeftButton) || hoveredSubControl != QStyle::SC_TitleBarLabel)
+    ensureWindowData();
+    if (!(event->buttons() & Qt::LeftButton) || windowData->hoveredSubControl != QStyle::SC_TitleBarLabel)
         return;
 
     QLineF delta(q->mapFromScene(event->buttonDownScenePos(Qt::LeftButton)), event->pos());
@@ -464,49 +452,56 @@ void QGraphicsWidgetPrivate::windowFrameMouseMoveEvent(QGraphicsSceneMouseEvent
     QLineF parentYDelta(q->mapToParent(QPointF(0, delta.p1().y())), q->mapToParent(QPointF(0, delta.p2().y())));
 
     QRectF newGeometry;
-    switch (grabbedSection) {
+    switch (windowData->grabbedSection) {
     case Qt::LeftSection:
-        newGeometry = QRectF(startGeometry.topLeft() + QPointF(parentXDelta.dx(), parentXDelta.dy()),
-                             startGeometry.size() - QSizeF(delta.dx(), delta.dy()));
+        newGeometry = QRectF(windowData->startGeometry.topLeft()
+                             + QPointF(parentXDelta.dx(), parentXDelta.dy()),
+                             windowData->startGeometry.size() - QSizeF(delta.dx(), delta.dy()));
         break;
     case Qt::TopLeftSection:
-        newGeometry = QRectF(startGeometry.topLeft() + QPointF(parentDelta.dx(), parentDelta.dy()),
-                             startGeometry.size() - QSizeF(delta.dx(), delta.dy()));
+        newGeometry = QRectF(windowData->startGeometry.topLeft()
+                             + QPointF(parentDelta.dx(), parentDelta.dy()),
+                             windowData->startGeometry.size() - QSizeF(delta.dx(), delta.dy()));
         break;
     case Qt::TopSection:
-        newGeometry = QRectF(startGeometry.topLeft() + QPointF(parentYDelta.dx(), parentYDelta.dy()),
-                             startGeometry.size() - QSizeF(0, delta.dy()));
+        newGeometry = QRectF(windowData->startGeometry.topLeft()
+                             + QPointF(parentYDelta.dx(), parentYDelta.dy()),
+                             windowData->startGeometry.size() - QSizeF(0, delta.dy()));
         break;
     case Qt::TopRightSection:
-        newGeometry = QRectF(startGeometry.topLeft() + QPointF(parentYDelta.dx(), parentYDelta.dy()),
-                             startGeometry.size() - QSizeF(-delta.dx(), delta.dy()));
+        newGeometry = QRectF(windowData->startGeometry.topLeft()
+                             + QPointF(parentYDelta.dx(), parentYDelta.dy()),
+                             windowData->startGeometry.size() - QSizeF(-delta.dx(), delta.dy()));
         break;
     case Qt::RightSection:
-        newGeometry = QRectF(startGeometry.topLeft(),
-                             startGeometry.size() + QSizeF(delta.dx(), 0));
+        newGeometry = QRectF(windowData->startGeometry.topLeft(),
+                             windowData->startGeometry.size() + QSizeF(delta.dx(), 0));
         break;
     case Qt::BottomRightSection:
-        newGeometry = QRectF(startGeometry.topLeft(),
-                             startGeometry.size() + QSizeF(delta.dx(), delta.dy()));
+        newGeometry = QRectF(windowData->startGeometry.topLeft(),
+                             windowData->startGeometry.size() + QSizeF(delta.dx(), delta.dy()));
         break;
     case Qt::BottomSection:
-        newGeometry = QRectF(startGeometry.topLeft(),
-                             startGeometry.size() + QSizeF(0, delta.dy()));
+        newGeometry = QRectF(windowData->startGeometry.topLeft(),
+                             windowData->startGeometry.size() + QSizeF(0, delta.dy()));
         break;
     case Qt::BottomLeftSection:
-        newGeometry = QRectF(startGeometry.topLeft() + QPointF(parentXDelta.dx(), parentXDelta.dy()),
-                             startGeometry.size() - QSizeF(delta.dx(), -delta.dy()));
+        newGeometry = QRectF(windowData->startGeometry.topLeft()
+                             + QPointF(parentXDelta.dx(), parentXDelta.dy()),
+                             windowData->startGeometry.size() - QSizeF(delta.dx(), -delta.dy()));
         break;
     case Qt::TitleBarArea:
-        newGeometry = QRectF(startGeometry.topLeft() + QPointF(parentDelta.dx(), parentDelta.dy()),
-                             startGeometry.size());
+        newGeometry = QRectF(windowData->startGeometry.topLeft()
+                             + QPointF(parentDelta.dx(), parentDelta.dy()),
+                             windowData->startGeometry.size());
         break;
     case Qt::NoSection:
         break;
     }
 
-    if (grabbedSection != Qt::NoSection) {
-        _q_boundGeometryToSizeConstraints(startGeometry, &newGeometry, grabbedSection,
+    if (windowData->grabbedSection != Qt::NoSection) {
+        _q_boundGeometryToSizeConstraints(windowData->startGeometry, &newGeometry,
+                                          windowData->grabbedSection,
                                           q->effectiveSizeHint(Qt::MinimumSize),
                                           q->effectiveSizeHint(Qt::MaximumSize));
         q->setGeometry(newGeometry);
@@ -519,21 +514,25 @@ void QGraphicsWidgetPrivate::windowFrameHoverMoveEvent(QGraphicsSceneHoverEvent
     if (!hasDecoration())
         return;
 
+    ensureWindowData();
+
     if (q->rect().contains(event->pos())) {
-        if (buttonMouseOver || hoveredSubControl != QStyle::SC_None)
+        if (windowData->buttonMouseOver || windowData->hoveredSubControl != QStyle::SC_None)
             windowFrameHoverLeaveEvent(event);
         return;
     }
 
-    bool wasMouseOver = buttonMouseOver;
-    QRect oldButtonRect = buttonRect;
-    buttonRect = QRect();
-    buttonMouseOver = false;
+    bool wasMouseOver = windowData->buttonMouseOver;
+    QRect oldButtonRect = windowData->buttonRect;
+    windowData->buttonRect = QRect();
+    windowData->buttonMouseOver = false;
     QPointF pos = event->pos();
     QStyleOptionTitleBar bar;
     // make sure that the coordinates (rect and pos) we send to the style are positive.
-    pos.rx() += leftWindowFrameMargin;
-    pos.ry() += topWindowFrameMargin;
+    if (windowFrameMargins) {
+        pos.rx() += windowFrameMargins[Left];
+        pos.ry() += windowFrameMargins[Top];
+    }
     initStyleOptionTitleBar(&bar);
     bar.rect = q->windowFrameRect().toRect();
     bar.rect.moveTo(0,0);
@@ -559,14 +558,17 @@ void QGraphicsWidgetPrivate::windowFrameHoverMoveEvent(QGraphicsSceneHoverEvent
             cursorShape = Qt::SizeVerCursor;
             break;
         case Qt::TitleBarArea:
-            buttonRect = q->style()->subControlRect(QStyle::CC_TitleBar, &bar, QStyle::SC_TitleBarCloseButton, 0);
+            windowData->buttonRect = q->style()->subControlRect(
+                QStyle::CC_TitleBar, &bar, QStyle::SC_TitleBarCloseButton, 0);
 #ifdef Q_WS_MAC
             // On mac we should hover if we are in the 'area' of the buttons
-            buttonRect |= q->style()->subControlRect(QStyle::CC_TitleBar, &bar, QStyle::SC_TitleBarMinButton, 0);
-            buttonRect |= q->style()->subControlRect(QStyle::CC_TitleBar, &bar, QStyle::SC_TitleBarMaxButton, 0);
+            windowData->buttonRect |= q->style()->subControlRect(
+                QStyle::CC_TitleBar, &bar, QStyle::SC_TitleBarMinButton, 0);
+            windowData->buttonRect |= q->style()->subControlRect(
+                QStyle::CC_TitleBar, &bar, QStyle::SC_TitleBarMaxButton, 0);
 #endif
-            if (buttonRect.contains(pos.toPoint()))
-                buttonMouseOver = true;
+            if (windowData->buttonRect.contains(pos.toPoint()))
+                windowData->buttonMouseOver = true;
             event->ignore();
             break;
         default:
@@ -578,15 +580,15 @@ void QGraphicsWidgetPrivate::windowFrameHoverMoveEvent(QGraphicsSceneHoverEvent
         q->setCursor(cursorShape);
 #endif
     // update buttons if we hover over them
-    hoveredSubControl = q->style()->hitTestComplexControl(QStyle::CC_TitleBar, &bar, pos.toPoint(), 0);
-    if (hoveredSubControl != QStyle::SC_TitleBarCloseButton)
-        hoveredSubControl = QStyle::SC_TitleBarLabel;
+    windowData->hoveredSubControl = q->style()->hitTestComplexControl(QStyle::CC_TitleBar, &bar, pos.toPoint(), 0);
+    if (windowData->hoveredSubControl != QStyle::SC_TitleBarCloseButton)
+        windowData->hoveredSubControl = QStyle::SC_TitleBarLabel;
 
-    if (buttonMouseOver != wasMouseOver) {
+    if (windowData->buttonMouseOver != wasMouseOver) {
         if (!oldButtonRect.isNull())
             q->update(QRectF(oldButtonRect).translated(q->windowFrameRect().topLeft()));
-        if (!buttonRect.isNull())
-            q->update(QRectF(buttonRect).translated(q->windowFrameRect().topLeft()));
+        if (!windowData->buttonRect.isNull())
+            q->update(QRectF(windowData->buttonRect).translated(q->windowFrameRect().topLeft()));
     }
 }
 
@@ -600,16 +602,19 @@ void QGraphicsWidgetPrivate::windowFrameHoverLeaveEvent(QGraphicsSceneHoverEvent
         q->unsetCursor();
 #endif
 
+        ensureWindowData();
+
         bool needsUpdate = false;
-        if (hoveredSubControl == QStyle::SC_TitleBarCloseButton || buttonMouseOver)
+        if (windowData->hoveredSubControl == QStyle::SC_TitleBarCloseButton
+            || windowData->buttonMouseOver)
             needsUpdate = true;
 
         // update the hover state (of buttons etc...)
-        hoveredSubControl = QStyle::SC_None;
-        buttonMouseOver = false;
-        buttonRect = QRect();
+        windowData->hoveredSubControl = QStyle::SC_None;
+        windowData->buttonMouseOver = false;
+        windowData->buttonRect = QRect();
         if (needsUpdate)
-            q->update(buttonRect);
+            q->update(windowData->buttonRect);
     }
 }
 
diff --git a/src/gui/graphicsview/qgraphicswidget_p.h b/src/gui/graphicsview/qgraphicswidget_p.h
index 53eaa31..3509a54 100644
--- a/src/gui/graphicsview/qgraphicswidget_p.h
+++ b/src/gui/graphicsview/qgraphicswidget_p.h
@@ -73,14 +73,7 @@ class Q_GUI_EXPORT QGraphicsWidgetPrivate : public QGraphicsItemPrivate
     Q_DECLARE_PUBLIC(QGraphicsWidget)
 public:
     QGraphicsWidgetPrivate()
-        : leftMargin(0),
-          topMargin(0),
-          rightMargin(0),
-          bottomMargin(0),
-          leftLayoutItemMargin(0),
-          topLayoutItemMargin(0),
-          rightLayoutItemMargin(0),
-          bottomLayoutItemMargin(0),
+        : margins(0),
           layout(0),
           inheritedPaletteResolveMask(0),
           inheritedFontResolveMask(0),
@@ -92,40 +85,23 @@ public:
           focusPrev(0),
           focusChild(0),
           windowFlags(0),
-          hoveredSubControl(QStyle::SC_None),
-          grabbedSection(Qt::NoSection),
-          buttonMouseOver(false),
-          buttonSunken(false),
+          windowData(0),
           setWindowFrameMargins(false),
-          leftWindowFrameMargin(0),
-          topWindowFrameMargin(0),
-          rightWindowFrameMargin(0),
-          bottomWindowFrameMargin(0)
+          windowFrameMargins(0)
     { }
+    virtual ~QGraphicsWidgetPrivate();
 
     void init(QGraphicsItem *parentItem, Qt::WindowFlags wFlags);
     qreal titleBarHeight(const QStyleOptionTitleBar &options) const;
 
     // Margins
-    qreal leftMargin;
-    qreal topMargin;
-    qreal rightMargin;
-    qreal bottomMargin;
-    QRectF contentsRect;
-
-    // Layout item margins
-    void getLayoutItemMargins(qreal *left, qreal *top, qreal *right, qreal *bottom) const;
-    void setLayoutItemMargins(qreal left, qreal top, qreal right, qreal bottom);
-    void setLayoutItemMargins(QStyle::SubElement element, const QStyleOption *opt = 0);
+    enum {Left, Top, Right, Bottom};
+    mutable qreal *margins;
+    void ensureMargins() const;
 
     void fixFocusChainBeforeReparenting(QGraphicsWidget *newParent, QGraphicsScene *newScene = 0);
     void setLayout_helper(QGraphicsLayout *l);
 
-    qreal leftLayoutItemMargin;
-    qreal topLayoutItemMargin;
-    qreal rightLayoutItemMargin;
-    qreal bottomLayoutItemMargin;
-
     // Layouts
     QGraphicsLayout *layout;
     void setLayoutDirection_helper(Qt::LayoutDirection direction);
@@ -208,20 +184,26 @@ public:
 
     // Windows
     Qt::WindowFlags windowFlags;
-    QString windowTitle;
-    QStyle::SubControl hoveredSubControl;
-    Qt::WindowFrameSection grabbedSection;
-    uint buttonMouseOver : 1;
-    uint buttonSunken : 1;
-    QPointF mouseDelta; // to compensate for small error when interactively resizing
-    QRectF startGeometry;
-    QRect buttonRect;
+    struct WindowData {
+        QString windowTitle;
+        QStyle::SubControl hoveredSubControl;
+        Qt::WindowFrameSection grabbedSection;
+        uint buttonMouseOver : 1;
+        uint buttonSunken : 1;
+        QRectF startGeometry;
+        QRect buttonRect;
+        WindowData()
+            : hoveredSubControl(QStyle::SC_None)
+            , grabbedSection(Qt::NoSection)
+            , buttonMouseOver(false)
+            , buttonSunken(false)
+        {}
+    } *windowData;
+    void ensureWindowData();
 
     bool setWindowFrameMargins;
-    qreal leftWindowFrameMargin;
-    qreal topWindowFrameMargin;
-    qreal rightWindowFrameMargin;
-    qreal bottomWindowFrameMargin;
+    mutable qreal *windowFrameMargins;
+    void ensureWindowFrameMargins() const;
 
 #ifndef QT_NO_ACTION
     QList<QAction *> actions;