Show the more meaningful delegate's displayText in the playlist tooltips, rather than the naked Qt::ToolTipRole text.

Update issue 267
Status: Fixed
I've fixed the strange values for numeric fields and the length field - they
should now all show the same text as shown in the playlist.
I think it's going to be harder to inhibit the tooltip if all the text is
already displayed though.

src/playlistdelegates.cpp

@@ -20,6 +20,9 @@
 #include <QDateTime>
 #include <QLineEdit>
 #include <QPainter>
+#include <QToolTip>
+#include <QWhatsThis>
+#include <QHelpEvent>
 
 const int PlaylistDelegateBase::kMinHeight = 19;
 
@@ -99,6 +102,42 @@ QStyleOptionViewItemV4 PlaylistDelegateBase::Adjusted(const QStyleOptionViewItem
   return ret;
 }
 
+bool PlaylistDelegateBase::helpEvent(QHelpEvent *event, QAbstractItemView *view,
+                                     const QStyleOptionViewItem &option,
+                                     const QModelIndex &index) {
+  // This function is copied from QAbstractItemDelegate, and changed to show
+  // displayText() in the tooltip, rather than the index's naked
+  // Qt::ToolTipRole text.
+
+  Q_UNUSED(option);
+
+  if (!event || !view)
+    return false;
+
+  QHelpEvent *he = static_cast<QHelpEvent*>(event);
+  QString text = displayText(index.data(), QLocale::system());
+
+  if (text.isEmpty() || !he)
+    return false;
+
+  switch (event->type()) {
+    case QEvent::ToolTip:
+      QToolTip::showText(he->globalPos(), text, view);
+      return true;
+
+    case QEvent::QueryWhatsThis:
+      return true;
+
+    case QEvent::WhatsThis:
+      QWhatsThis::showText(he->globalPos(), text, view);
+      return true;
+
+    default:
+      break;
+  }
+  return false;
+}
+
 
 QString LengthItemDelegate::displayText(const QVariant& value, const QLocale&) const {
   bool ok = false;

src/playlistdelegates.h

@@ -37,6 +37,10 @@ class PlaylistDelegateBase : public QStyledItemDelegate {
 
   static const int kMinHeight;
 
+ public slots:
+  bool helpEvent(QHelpEvent *event, QAbstractItemView *view,
+                 const QStyleOptionViewItem &option, const QModelIndex &index);
+
  protected:
   QTreeView* view_;
 };