Fix the mouse interaction model of the sidebar icon list

to allow changing sidebar pages by keeping the left mouse
button pressed and moving the cursor over the icon list,
similar to a popup menu or the treelist version of the
tab bar in Konversation.

A remaining bug in the sidebar is that switching iconlist
items using the keyboard arrow keys won't switch sidebar
pages. I will fix that next time, unless someone else is
faster.

svn path=/trunk/KDE/kdegraphics/okular/; revision=1034540

ui/sidebar.cpp

@@ -1,5 +1,6 @@
 /***************************************************************************
  *   Copyright (C) 2007 by Pino Toscano <pino@kde.org>                     *
+ *   Copyright (C) 2009 by Eike Hein <hein@kde.org>                        *
  *                                                                         *
  *   This program is free software; you can redistribute it and/or modify  *
  *   it under the terms of the GNU General Public License as published by  *
@@ -187,6 +188,8 @@ QSize SidebarDelegate::sizeHint( const QStyleOptionViewItem &option, const QMode
 /* A custom list widget that ignores the events for disabled items */
 class SidebarListWidget : public QListWidget
 {
+
+
     public:
         SidebarListWidget( QWidget *parent = 0 );
         ~SidebarListWidget();
@@ -199,11 +202,26 @@ class SidebarListWidget : public QListWidget
         void mouseReleaseEvent( QMouseEvent *event );
 
         QModelIndex moveCursor( QAbstractItemView::CursorAction cursorAction, Qt::KeyboardModifiers modifiers );
+
+    private:
+        // These two are used to keep track of the row an initial mousePress-
+        // Event() occurs on and the row the cursor moves over while the left
+        // mouse button is pressed, respectively, as well as for event compre-
+        // ssion, to avoid calling SideBar::itemClicked() multiple times for
+        // the same item in a row on mouseMoveEvent()'s. This code is written
+        // under the assumption that the number and positions of items in the
+        // list won't change while the user interacts with it using the mouse.
+        // Future work here must see to that this assumption continues to hold
+        // up, or achieve calling SideBar::itemClicked() differently.
+        int mousePressedRow;
+        int rowUnderMouse;
 };
 
 SidebarListWidget::SidebarListWidget( QWidget *parent )
     : QListWidget( parent )
 {
+    mousePressedRow = -1;
+    rowUnderMouse = -1;
 }
 
 SidebarListWidget::~SidebarListWidget()
@@ -222,8 +240,25 @@ void SidebarListWidget::mouseDoubleClickEvent( QMouseEvent *event )
 void SidebarListWidget::mouseMoveEvent( QMouseEvent *event )
 {
     QModelIndex index = indexAt( event->pos() );
-    if ( index.isValid() && !( index.flags() & Qt::ItemIsSelectable ) )
-        return;
+
+    if ( index.isValid() )
+    {
+        if ( index.flags() & Qt::ItemIsSelectable )
+        {
+            if ( event->buttons() & Qt::LeftButton
+                 && index.row() != mousePressedRow
+                 && index.row() != rowUnderMouse )
+            {
+                mousePressedRow = -1;
+                rowUnderMouse = index.row();
+
+                QMetaObject::invokeMethod(parent(), "itemClicked", Qt::DirectConnection,
+                    Q_ARG(QListWidgetItem*, item(index.row())));
+            }
+        }
+        else
+            return;
+    }
 
     QListWidget::mouseMoveEvent( event );
 }
@@ -231,8 +266,17 @@ void SidebarListWidget::mouseMoveEvent( QMouseEvent *event )
 void SidebarListWidget::mousePressEvent( QMouseEvent *event )
 {
     QModelIndex index = indexAt( event->pos() );
-    if ( index.isValid() && !( index.flags() & Qt::ItemIsSelectable ) )
-        return;
+
+    if ( index.isValid() )
+    {
+        if ( index.flags() & Qt::ItemIsSelectable )
+        {
+            if ( event->buttons() & Qt::LeftButton )
+                mousePressedRow = index.row();
+        }
+        else
+            return;
+    }
 
     QListWidget::mousePressEvent( event );
 }
@@ -240,8 +284,29 @@ void SidebarListWidget::mousePressEvent( QMouseEvent *event )
 void SidebarListWidget::mouseReleaseEvent( QMouseEvent *event )
 {
     QModelIndex index = indexAt( event->pos() );
-    if ( index.isValid() && !( index.flags() & Qt::ItemIsSelectable ) )
-        return;
+
+    if ( index.isValid() )
+    {
+        if ( index.flags() & Qt::ItemIsSelectable )
+        {
+            if ( event->button() == Qt::LeftButton
+                 && index.row() != rowUnderMouse )
+            {
+                QMetaObject::invokeMethod(parent(), "itemClicked", Qt::DirectConnection,
+                    Q_ARG(QListWidgetItem*, item(index.row())));
+            }
+        }
+        else
+        {
+            mousePressedRow = -1;
+            rowUnderMouse = -1;
+
+            return;
+        }
+    }
+
+    mousePressedRow = -1;
+    rowUnderMouse = -1;
 
     QListWidget::mouseReleaseEvent( event );
 }
@@ -408,7 +473,6 @@ Sidebar::Sidebar( QWidget *parent )
     d->vlay->addWidget( d->stack );
     d->sideContainer->hide();
 
-    connect( d->list, SIGNAL( itemClicked( QListWidgetItem* ) ), this, SLOT( itemClicked( QListWidgetItem* ) ) );
     connect( d->list, SIGNAL( customContextMenuRequested( const QPoint & ) ),
              this, SLOT( listContextMenu( const QPoint & ) ) );
     connect( d->splitter, SIGNAL( splitterMoved( int, int ) ), this, SLOT( splitterMoved( int, int ) ) );