Reading the documentation, I have come up with the following ugly piece of code:
int GetCellHeight (TreeView tree)
{
if (_cellHeight > 0) {
return _cellHeight;
}
int offsetX;
int offsetY;
int cellWidth;
Gdk.Rectangle rectangle = new Gdk.Rectangle ();
TreeViewColumn column = tree.GetColumn (0);
// Getting dimensions from TreeViewColumn
column.CellGetSize(rectangle, out offsetX, out offsetY,
out cellWidth, out _cellHeight);
// And now get padding from CellRenderer
CellRenderer renderer = column.CellRenderers[0];
_cellHeight += (int)renderer.Ypad;
return _cellHeight;
}
This is what it looks like now: