Get Pixel Position of Item or Cell Height in Treeview

Question

In a GTK# application, I am using a TreeView inside a ScrolledWindow, and try to find the position of an item inside the TreeStore to draw lines starting from that item in Cairo. For now, I am using a hard coded value for cell height, which works for few items, but when other font sizes are used or the item list gets longer, there is a visible offset. Is there a method to get the cell height of a TreeView, or another way to get the vertical position of an item in the TreeStore?

Here is the method, that I currently use:

int GetYPositionForPort (TreeView tree, TreeStore store, Port selectedPort)
{
    // Is there a way to get the cell height?
    int cellHeight = 24;
    // We start in the middle of the first Treeview item
    int position = cellHeight / 2;

    ScrolledWindow treeParent = tree.Parent as ScrolledWindow;
    if (treeParent != null) {
        position -= Convert.ToInt32 (treeParent.Vadjustment.Value);
    }
    TreeIter clientIter;
    TreeIter portIter;
    if (store.GetIterFirst (out clientIter)) {
        do {
            if (store.IterHasChild (clientIter) 
                && tree.GetRowExpanded (store.GetPath (clientIter))) {
                if (store.IterChildren (out portIter, clientIter)) {
                    do {
                        position += cellHeight;
                    } while (((Port)store.GetValue(portIter, 0) != selectedPort 
                        || (Client)store.GetValue(clientIter, 0) != selectedPort.Client) 
                        && store.IterNext(ref portIter));
                }
            }
            //Necessary because the first Treeview item only counts as 1/2 cell height.
            if (((Client)store.GetValue (clientIter, 0)) == selectedPort.Client) {
                break;
            }
            position += cellHeight;
        } while (store.IterNext(ref clientIter));
    }
    return position;
}

You can see the error on the bottom of the screenshot where the lines are not aligned with the items in the TreeView:

Answer 1

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: