C++ code excerpts for question about a simpler way to support in-cell text
editing of only a single column within a Qt 4.4 QTreeWidget. (Only top-level
QTreeWidgetItems are used -- this is just a list, not an actual treeview).

Auth: Phil Weinstein, CADSWES
Date: 9-17-2009
Ref:  http://cadswes2.colorado.edu/~philw/2009/QtQuestions/QTreeWidgetEditing/ 

// ******************
// ***  Contents  ***
// ******************

(1) Some Module Definitions

(2) Three Class Declarations:

  class GreenBookConfigPanel               : public QWidget
  class GreenBookConfigPanel::SlotTree     : public QTreeWidget
  class GreenBookConfigPanel::SlotTreeItem : public QTreeWidgetItem

(3) Relevant Method Definitions

  void GreenBookConfigPanel::initConnections()
  void GreenBookConfigPanel::disableSlotTreeItemEditing ()

  void GreenBookConfigPanel::slotsTree_itemSelectChanged ()
  void GreenBookConfigPanel::slotsTree_itemActivated (..)
  void GreenBookConfigPanel::slotsTree_itemClicked (..)
  void GreenBookConfigPanel::slotsTree_itemDoubleClicked (..)
  void GreenBookConfigPanel::slotsTree_itemChanged (..)

  GreenBookConfigPanel::SlotTreeItem::SlotTreeItem (QTreeWidget* parent, )
  void GreenBookConfigPanel::SlotTreeItem::enableItemEditing (bool ena)
  void GreenBookConfigPanel::SlotTreeItem::processCellEdit (int col)

//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------

// *************************************
// ***  (1) Some Module Definitions  ***
// *************************************

// QTreeWidget* _slotsTreeWidget Columns
static const int SLOT_COL_ORD        (0);  // ordinal
static const int SLOT_COL_SLOT_NAME  (1);  // full slot name
static const int SLOT_COL_TIMESTEP   (2);  // step size
static const int SLOT_COL_USER_LAB   (3);  // user provided column label
static const int SLOT_COL_SHOW_SUM   (4);  // toggle: show column sum
static const int SLOT_COL_SHOW_MEAN  (5);  // toggle: ... mean
static const int SLOT_COL_SHOW_MIN   (6);  // toggle: ... minimum
static const int SLOT_COL_SHOW_MAX   (7);  // toggle: ... maximum
static const int SLOT_COL_SHOW_START (8);  // toggle: ... first value
static const int SLOT_COL_SHOW_END   (9);  // toggle: ... last value

//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------

// **************************************
// ***  (2) Three Class Declarations  ***
// **************************************

class GreenBookConfigPanel : public QWidget
{
 Q_OBJECT

 private:
  class SlotTree;      // : public QTreeWidget     -- declared below
  class SlotTreeItem;  // : public QTreeWidgetItem -- declared below

 ... ... ...

 private
   // Widget Handles
   SlotTree* _slotsTreeWidget;

 ... ... ...

 private slots:
   void slotsTree_itemSelectChanged ();
   void slotsTree_itemActivated     (QTreeWidgetItem*, int col);
   void slotsTree_itemClicked       (QTreeWidgetItem*, int col);
   void slotsTree_itemDoubleClicked (QTreeWidgetItem*, int col);
   void slotsTree_itemChanged       (QTreeWidgetItem*, int col);

 ... ... ...
};

//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------

class GreenBookConfigPanel::SlotTree : public QTreeWidget
{
  private:
    GreenBookConfigPanel* _panel;

  public:
    SlotTree (GreenBookConfigPanel*);

  protected:
    // virtual from QAbstractScrollArea
    virtual void contextMenuEvent (QContextMenuEvent*);
};

//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------

class GreenBookConfigPanel::SlotTreeItem : public QTreeWidgetItem
{
    ... ... ...

  private:
    QTreeWidget* _parentTreeWidget;
    SlotRec _slotRec;
    int _ord;

  public:
    SlotTreeItem (QTreeWidget*, const SlotRec&, int ord=(-1));
    virtual ~SlotTreeItem();

    ... ... ...

    void enableItemEditing (bool);
    void processCellEdit (int col);

    ... ... ...
};

//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------

// *****************************************
// ***  (3) Relevant Method Definitions  ***
// *****************************************

void GreenBookConfigPanel::initConnections()
{
   ... ... ...

   // *****************************************
   // ***  Slot List TreeWidget (TreeView)  ***
   // *****************************************

   connect (_slotsTreeWidget,
            SIGNAL (itemSelectionChanged()),
            SLOT (slotsTree_itemSelectChanged()));

   connect (_slotsTreeWidget,
            SIGNAL (itemActivated (QTreeWidgetItem*, int)),
            SLOT (slotsTree_itemActivated (QTreeWidgetItem*, int)));

   connect (_slotsTreeWidget,
            SIGNAL (itemClicked (QTreeWidgetItem*, int)),
            SLOT (slotsTree_itemClicked (QTreeWidgetItem*, int)));

   connect (_slotsTreeWidget,
            SIGNAL (itemDoubleClicked (QTreeWidgetItem*, int)),
            SLOT (slotsTree_itemDoubleClicked (QTreeWidgetItem*, int)));

   connect (_slotsTreeWidget,
            SIGNAL (itemChanged (QTreeWidgetItem*, int)),
            SLOT (slotsTree_itemChanged (QTreeWidgetItem*, int)));

   ... ... ...
}

//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------

void GreenBookConfigPanel::disableSlotTreeItemEditing()
{
   const int topItemCnt = _slotsTreeWidget->topLevelItemCount();
   for (int inx = 0;  inx < topItemCnt;  ++inx)
   {
      QTreeWidgetItem* item = _slotsTreeWidget->topLevelItem (inx);
      SlotTreeItem* slotItem = dynamic_cast<SlotTreeItem*> (item);

      if (slotItem)
      {
         slotItem->enableItemEditing (false);
      }
   }
}

//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------

void GreenBookConfigPanel::slotsTree_itemSelectChanged()
{
   disableSlotTreeItemEditing();
   sensitizeWidgets();

   emit slotSelectionChanged();
}

//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------

void GreenBookConfigPanel::slotsTree_itemActivated (
                               QTreeWidgetItem* item, int col)
{
   SlotTreeItem* slotItem = dynamic_cast<SlotTreeItem*> (item);
   if (slotItem)
   {
      disableSlotTreeItemEditing();
   }

   sensitizeWidgets();
}

//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------

void GreenBookConfigPanel::slotsTree_itemClicked (
                               QTreeWidgetItem* item, int col)
{
   SlotTreeItem* slotItem = dynamic_cast<SlotTreeItem*> (item);
   if (slotItem)
   {
      // This will have an effect only on relevant columns.
      slotItem->toggleColumnSwitch (col);

      disableSlotTreeItemEditing();
   }

   sensitizeWidgets();
}

//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------

void GreenBookConfigPanel::slotsTree_itemDoubleClicked (
                               QTreeWidgetItem* item, int col)
{
   SlotTreeItem* slotItem = dynamic_cast<SlotTreeItem*> (item);
   if (slotItem)
   {
      disableSlotTreeItemEditing();

      if (col == SLOT_COL_USER_LAB)
      {
         slotItem->enableItemEditing (true);
         _slotsTreeWidget->editItem (slotItem, col);
      }

      if (col == SLOT_COL_SLOT_NAME)
      {
         Slot* slotPtr = slotItem->locateSlot();
         if (slotPtr)
         {
            QGui::openSlot (slotPtr);
         }
      }
   }

   sensitizeWidgets();
}

//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------

void GreenBookConfigPanel::slotsTree_itemChanged (
                               QTreeWidgetItem* item, int col)
{
   SlotTreeItem* slotItem = dynamic_cast<SlotTreeItem*> (item);
   if (slotItem)
   {
      slotItem->processCellEdit (col);
   }
}

//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------

// constructor 1 of 1
GreenBookConfigPanel::SlotTreeItem::SlotTreeItem (QTreeWidget* parent,
                                                  const SlotRec& rec,
                                                  int ord /*=(-1)*/)
  : QTreeWidgetItem (parent),
    _parentTreeWidget (parent),
    _slotRec (rec),
    _ord (ord)
{
   ... ... ...

   // disable item editing
   enableItemEditing (false);
}

//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------

void GreenBookConfigPanel::SlotTreeItem::enableItemEditing (bool ena)
{
   const Qt::ItemFlags oldFlags (flags());
   Qt::ItemFlags newFlags (oldFlags);

   if (ena)
   {
      newFlags = (oldFlags | Qt::ItemIsEditable);
   }
   else
   {
      newFlags = (oldFlags & (~Qt::ItemIsEditable));
   }

   if (newFlags != oldFlags)
   {
      setFlags (newFlags);
   }
}

//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------

void GreenBookConfigPanel::SlotTreeItem::processCellEdit (int col)
{
   const QString editText = text (col);
   const QString trimText = editText.trimmed();
   const QString padText = pad1 + trimText + pad2;

   if (col == SLOT_COL_USER_LAB)
   {
      enableItemEditing (false);

      const QString oldText = _slotRec._userColLabel;

      if (oldText != trimText)
      {
         _slotRec._userColLabel = trimText;
      }

      if (editText != padText)
      {
         setText (col, padText);
      }
   }
}

--- (end) ---