Planner: show new icon to indicate that last point can't be deleted

Having the trash can disappear is somewhat intuitive, but I'd argue this
is even more so.

Fixes #789

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

qt-models/cleanertablemodel.h

@@ -7,6 +7,7 @@
 
 /* Retrieve the trash icon pixmap, common to most table models */
 const QPixmap &trashIcon();
+const QPixmap &trashForbiddenIcon();
 
 /* When using a QAbstractTableModel, consider using this instead
  * of the default implementation, as it's easyer to setup the columns

qt-models/diveplannermodel.cpp

@@ -218,12 +218,16 @@ QVariant DivePlannerPointsModel::data(const QModelIndex &index, int role) const
 		case REMOVE:
 			if (rowCount() > 1)
 				return p.entered ? trashIcon() : QVariant();
+			else
+				return trashForbiddenIcon();
 		}
 	} else if (role == Qt::SizeHintRole) {
 		switch (index.column()) {
 		case REMOVE:
 			if (rowCount() > 1)
 				return p.entered ? trashIcon().size() : QVariant();
+			else
+				return trashForbiddenIcon().size();
 		}
 	} else if (role == Qt::FontRole) {
 		if (divepoints.at(index.row()).entered) {

qt-models/models.cpp

@@ -18,6 +18,11 @@ const QPixmap &trashIcon()
 	return trash;
 }
 
+const QPixmap &trashForbiddenIcon()
+{
+	static QPixmap trash = QPixmap(":trashForbidden").scaledToHeight(defaultIconMetrics().sz_small);
+	return trash;
+}
 
 Qt::ItemFlags GasSelectionModel::flags(const QModelIndex &index) const
 {