From 60eabf5382ff58c02000a25d4c98b8aa2416f13e Mon Sep 17 00:00:00 2001
From: Marco Martin <notmart@gmail.com>
Date: Fri, 6 Nov 2009 18:57:35 +0000
Subject: [PATCH] void registerAsDragHandle(QGraphicsItem *item); easy way to
 keep the flickable scrolling even with clickable sub items

svn path=/trunk/KDE/kdelibs/; revision=1045776
---
 widgets/scrollwidget.cpp | 47 ++++++++++++++++++++++++++++++++++++++++
 widgets/scrollwidget.h   | 20 +++++++++++++++++
 2 files changed, 67 insertions(+)

diff --git a/widgets/scrollwidget.cpp b/widgets/scrollwidget.cpp
index 1b752aa0e..e5167870b 100644
--- a/widgets/scrollwidget.cpp
+++ b/widgets/scrollwidget.cpp
@@ -21,6 +21,7 @@
 //Qt
 #include <QGraphicsSceneResizeEvent>
 #include <QGraphicsGridLayout>
+#include <QGraphicsScene>
 #include <QApplication>
 #include <QWidget>
 #include <QTimer>
@@ -227,6 +228,7 @@ public:
     Qt::ScrollBarPolicy horizontalScrollBarPolicy;
     QString styleSheet;
     QRectF rectToBeVisible;
+    QSet<QGraphicsItem *>dragHandles;
     bool dragging;
     int animId;
     static const int borderSize = 4;
@@ -343,6 +345,33 @@ void ScrollWidget::ensureItemVisible(QGraphicsItem *item)
     QTimer::singleShot(0, this, SLOT(makeRectVisible()));
 }
 
+void ScrollWidget::registerAsDragHandle(QGraphicsItem *item)
+{
+    if (!d->widget || !item) {
+        return;
+    }
+
+    QGraphicsItem *parentOfItem = item->parentItem();
+    while (parentOfItem != d->widget) {
+        if (!parentOfItem) {
+            return;
+        }
+
+        parentOfItem = parentOfItem->parentItem();
+    }
+
+    item->installSceneEventFilter(this);
+    d->dragHandles.insert(item);
+}
+
+void ScrollWidget::unregisterAsDragHandle(QGraphicsItem *item)
+{
+    if (item) {
+        item->removeSceneEventFilter(this);
+        d->dragHandles.remove(item);
+    }
+}
+
 QRectF ScrollWidget::viewportGeometry() const
 {
     QRectF result;
@@ -453,6 +482,24 @@ void ScrollWidget::wheelEvent(QGraphicsSceneWheelEvent *event)
 
 }
 
+bool ScrollWidget::sceneEventFilter(QGraphicsItem *watched, QEvent *event)
+{
+    if (!scene()) {
+        return false;
+    }
+
+    if (d->dragHandles.contains(watched)) {
+        if (event->type() == QEvent::GraphicsSceneMousePress ||
+            event->type() == QEvent::GraphicsSceneMouseMove ||
+            event->type() == QEvent::GraphicsSceneMouseRelease) {
+            if (scene()) {
+                scene()->sendEvent(this, event);
+            }
+        }
+    }
+    return false;
+}
+
 bool ScrollWidget::eventFilter(QObject *watched, QEvent *event)
 {
     if (!d->widget) {
diff --git a/widgets/scrollwidget.h b/widgets/scrollwidget.h
index ea38d3c71..37cdf95d6 100644
--- a/widgets/scrollwidget.h
+++ b/widgets/scrollwidget.h
@@ -118,6 +118,25 @@ public:
      */
     void ensureItemVisible(QGraphicsItem *item);
 
+    /**
+     * Register an item as a drag handle, it means mouse events will pass trough it
+     * and will be possible to drag the view by dragging the item itself.
+     * The item will still receive mouse clicks if the mouse didn't move
+     * between press and release.
+     *
+     * @param item the drag handle item. widget() must be an ancestor if it in
+     *             the parent hierarchy. if item doesn't accept mose press events
+     *             it's not necessary to call this function.
+     * @since 4.4
+     */
+    void registerAsDragHandle(QGraphicsItem *item);
+
+    /**
+     * Unregister the given item as drag handle (if it was registered)
+     * @since 4.4
+     */
+    void unregisterAsDragHandle(QGraphicsItem *item);
+
     /**
      * The geometry of the viewport.
      * @since 4.4
@@ -172,6 +191,7 @@ protected:
     bool eventFilter(QObject *watched, QEvent *event);
     void focusInEvent(QFocusEvent *event);
     QSizeF sizeHint(Qt::SizeHint which, const QSizeF & constraint) const;
+    bool sceneEventFilter(QGraphicsItem *watched, QEvent *event);
 
 private:
     ScrollWidgetPrivate * const d;