Allow shorter playlist column names if header size is too small.

Fixes issue 201.

src/playlist/playlist.cpp

@@ -1108,6 +1108,20 @@ QString Playlist::column_name(Column column) {
   return "";
 }
 
+QString Playlist::abbreviated_column_name(Column column) {
+  const QString& column_name = Playlist::column_name(column);
+  switch (column) {
+    case Column_Disc:
+    case Column_PlayCount:
+    case Column_SkipCount:
+    case Column_Track:
+      return QString("%1#").arg(column_name[0]);
+    default: 
+      return column_name;
+  }
+  return "";
+}
+
 void Playlist::sort(int column, Qt::SortOrder order) {
   if (ignore_sorting_)
     return;

src/playlist/playlist.h

@@ -147,6 +147,8 @@ class Playlist : public QAbstractListModel {
                            PlaylistItemPtr a, PlaylistItemPtr b);
 
   static QString column_name(Column column);
+  static QString abbreviated_column_name(Column column);
+
   static bool column_is_editable(Playlist::Column column);
   static bool set_column_value(Song& song, Column column, const QVariant& value);
 

src/playlist/playlistview.cpp

@@ -49,6 +49,22 @@ PlaylistProxyStyle::PlaylistProxyStyle(QStyle* base)
 void PlaylistProxyStyle::drawControl(
     ControlElement element, const QStyleOption* option, QPainter* painter,
     const QWidget* widget) const {
+  if (element == CE_Header) {
+    const QStyleOptionHeader* header_option = qstyleoption_cast<const QStyleOptionHeader*>(option);
+    const QRect& rect = header_option->rect;
+    const QString& text = header_option->text;
+    const QFontMetrics& font_metrics = header_option->fontMetrics;
+    
+    // spaces added to make transition less abrupt
+    if (rect.width() < font_metrics.width(text + "  ")) {
+      const Playlist::Column column = static_cast<Playlist::Column>(header_option->section);
+      QStyleOptionHeader new_option(*header_option);
+      new_option.text = Playlist::abbreviated_column_name(column);
+      QProxyStyle::drawControl(element, &new_option, painter, widget);
+      return;
+    }
+  }
+
   if (element == CE_ItemViewItem)
     cleanlooks_->drawControl(element, option, painter, widget);
   else