BColumnListView: Enable invalidating rows, fix SetField()

* Seems like there was no easy way to simply invalidate
   a given BRow. Introduced BColumnListView::InvalidateRow().
 * BRow::SetField() tried to invalidate the row, but invalidated
   the listview instead of the BOutlineView responsible for
   drawing the list contents. Use the new InvaalidateRow().

headers/private/interface/ColumnListView.h

@@ -135,6 +135,8 @@ public:
 			bool 				IsExpanded() const;
 			bool				IsSelected() const;
 
+			void				Invalidate();
+
 private:
 	// Blows up into the debugger if the validation fails.
 			void				ValidateFields() const;
@@ -332,6 +334,8 @@ public:
 									parentRow1 = NULL, BRow* parentRow2 = NULL);
 			void				Clear();
 
+			void				InvalidateRow(BRow* row);
+
 	// Appearance (DEPRECATED)
 			void				GetFont(BFont* font) const
 									{ BView::GetFont(font); }

src/kits/interface/ColumnListView.cpp

@@ -500,9 +500,7 @@ BRow::SetField(BField* field, int32 logicalFieldIndex)
 
 	if (NULL != fList) {
 		ValidateField(field, logicalFieldIndex);
-		BRect inv;
+		Invalidate();
-		fList->GetRowRect(this, &inv);
-		fList->Invalidate(inv);
 	}
 
 	fFields.AddItem(field, logicalFieldIndex);
@@ -530,6 +528,14 @@ BRow::IsSelected() const
 }
 
 
+void
+BRow::Invalidate()
+{
+	if (fList != NULL)
+		fList->InvalidateRow(this);
+}
+
+
 void
 BRow::ValidateFields() const
 {
@@ -1340,6 +1346,15 @@ BColumnListView::Clear()
 }
 
 
+void
+BColumnListView::InvalidateRow(BRow* row)
+{
+	BRect updateRect;
+	GetRowRect(row, &updateRect);
+	fOutlineView->Invalidate(updateRect);
+}
+
+
 void
 BColumnListView::SetFont(const BFont* font, uint32 mask)
 {