Merge layout requests to avoid unnecessary recalculations

It improves the layout performance by avoiding intermediate
recalculations, merging all requests into a single one.

Signed-off-by: Adriano Rezende <adriano.rezende@openbossa.org>

Merge-request: 12
Reviewed-by: Jens Bache-Wiig <jens.bache-wiig@nokia.com>

4 files changed, 67 insertions, 15 deletions

diff --git a/src/qdeclarativelayout.cpp b/src/qdeclarativelayout.cpp
index ae675e17..64af622e 100644
--- a/src/qdeclarativelayout.cpp
+++ b/src/qdeclarativelayout.cpp
@@ -38,6 +38,8 @@
 ****************************************************************************/
 
 #include "qdeclarativelayout.h"
+#include <QEvent>
+#include <QApplication>
 #include <QtCore/qnumeric.h>
 
 
@@ -117,7 +119,8 @@ void QDeclarativeLayoutAttached::updateLayout()
 
 
 QDeclarativeLayout::QDeclarativeLayout(QDeclarativeItem *parent)
-    : QDeclarativeItem(parent)
+    : QDeclarativeItem(parent),
+      m_dirty(false)
 {
 
 }
@@ -138,3 +141,53 @@ QDeclarativeLayoutAttached *QDeclarativeLayout::qmlAttachedProperties(QObject *o
 {
     return new QDeclarativeLayoutAttached(object);
 }
+
+bool QDeclarativeLayout::event(QEvent *e)
+{
+    if (e->type() == QEvent::LayoutRequest)
+        reconfigureTopDown();
+
+    return QDeclarativeItem::event(e);
+}
+
+void QDeclarativeLayout::invalidate()
+{
+    if (m_dirty)
+        return;
+
+    QDeclarativeLayout *layout = this;
+    QDeclarativeLayout *parentLayout = 0;
+
+    while (layout) {
+        layout->m_dirty = true;
+        parentLayout = qobject_cast<QDeclarativeLayout *>(layout->parentItem());
+
+        if (!parentLayout)
+            break;
+        else
+            layout = parentLayout;
+    }
+
+    QApplication::postEvent(layout, new QEvent(QEvent::LayoutRequest));
+}
+
+void QDeclarativeLayout::reconfigureTopDown()
+{
+    const QList<QGraphicsItem *> &children = childItems();
+
+    foreach (QGraphicsItem *child, children) {
+        QGraphicsObject *obj = child->toGraphicsObject();
+        QDeclarativeLayout *layout = obj ? qobject_cast<QDeclarativeLayout *>(obj) : 0;
+
+        if (layout && layout->m_dirty)
+            layout->reconfigureTopDown();
+    }
+
+    reconfigureLayout();
+    m_dirty = false;
+}
+
+void QDeclarativeLayout::reconfigureLayout()
+{
+
+}
diff --git a/src/qdeclarativelayout.h b/src/qdeclarativelayout.h
index 4abcd481..c5a8b470 100644
--- a/src/qdeclarativelayout.h
+++ b/src/qdeclarativelayout.h
@@ -63,10 +63,15 @@ public:
     static QDeclarativeLayoutAttached *qmlAttachedProperties(QObject *object);
 
 protected:
-    virtual void invalidate() = 0;
+    void invalidate();
+    bool event(QEvent *e);
+    void reconfigureTopDown();
+    virtual void reconfigureLayout();
     void setupItemLayout(QDeclarativeItem *item);
 
 private:
+    bool m_dirty;
+
     friend class QDeclarativeLayoutAttached;
 };
 
diff --git a/src/qdeclarativelinearlayout.cpp b/src/qdeclarativelinearlayout.cpp
index 399d27f5..b28838a6 100644
--- a/src/qdeclarativelinearlayout.cpp
+++ b/src/qdeclarativelinearlayout.cpp
@@ -64,7 +64,7 @@ void QDeclarativeLinearLayout::setSpacing(qreal spacing)
         return;
 
     m_spacing = spacing;
-    reconfigureLayout();
+    invalidate();
 }
 
 QDeclarativeLinearLayout::Orientation QDeclarativeLinearLayout::orientation() const
@@ -78,7 +78,7 @@ void QDeclarativeLinearLayout::setOrientation(Orientation orientation)
         return;
 
     m_orientation = orientation;
-    reconfigureLayout();
+    invalidate();
 
     emit orientationChanged();
 }
@@ -87,7 +87,7 @@ void QDeclarativeLinearLayout::componentComplete()
 {
     QDeclarativeLayout::componentComplete();
     updateLayoutItems();
-    reconfigureLayout();
+    invalidate();
 }
 
 void QDeclarativeLinearLayout::updateLayoutItems()
@@ -127,7 +127,7 @@ QVariant QDeclarativeLinearLayout::itemChange(GraphicsItemChange change, const Q
 void QDeclarativeLinearLayout::geometryChanged(const QRectF &newGeometry, const QRectF &oldGeometry)
 {
     QDeclarativeLayout::geometryChanged(newGeometry, oldGeometry);
-    reconfigureLayout();
+    invalidate();
 }
 
 void QDeclarativeLinearLayout::insertLayoutItem(QDeclarativeItem *item)
@@ -135,7 +135,7 @@ void QDeclarativeLinearLayout::insertLayoutItem(QDeclarativeItem *item)
     m_items.append(item);
     setupItemLayout(item);
 
-    reconfigureLayout();
+    invalidate();
     QObject::connect(item, SIGNAL(destroyed()), this, SLOT(onItemDestroyed()));
 }
 
@@ -144,7 +144,7 @@ void QDeclarativeLinearLayout::removeLayoutItem(QDeclarativeItem *item)
     if (!m_items.removeOne(item))
         return;
 
-    reconfigureLayout();
+    invalidate();
     QObject::disconnect(item, SIGNAL(destroyed()), this, SLOT(onItemDestroyed()));
 }
 
@@ -153,12 +153,7 @@ void QDeclarativeLinearLayout::onItemDestroyed()
     if (!m_items.removeOne(static_cast<QDeclarativeItem *>(sender())))
         return;
 
-    reconfigureLayout();
-}
-
-void QDeclarativeLinearLayout::invalidate()
-{
-    reconfigureLayout();
+    invalidate();
 }
 
 void QDeclarativeLinearLayout::reconfigureLayout()
diff --git a/src/qdeclarativelinearlayout.h b/src/qdeclarativelinearlayout.h
index 7e897356..ec207bfa 100644
--- a/src/qdeclarativelinearlayout.h
+++ b/src/qdeclarativelinearlayout.h
@@ -71,7 +71,6 @@ signals:
     void orientationChanged();
 
 protected:
-    void invalidate();
     void updateLayoutItems();
     void reconfigureLayout();
     void insertLayoutItem(QDeclarativeItem *item);