Question

I want to add a ToolTip to TreeView nodes and make a balloon appear at the mouse coordinates:

private void treeView1_MouseMove(object sender, MouseEventArgs e)
{
    node = treeView1.getNodeAt(e.X, e.Y);
    toolTip1 = new ToolTip();
    toolTip1.IsBalloon = true;
    toolTip1.InitialDelay = 500;
    toolTip1.SetToolTip(treeView1, node.Text);
}

The problem is that the ToolTip is assigned to the TreeView, not to the TreeNode, and the position of the balloon is quite strange – not at the expected mouse coordinates, but somewhere in treeView1.

I was trying to use toolTip1.Show() but the InitialDelay property is ignored.

How can I position a balloon ToolTip over a TreeNode and delay its display?

Answer 1

The ToolTip control is not necessary in order to display tooltips for the TreeNodes. The TreeView has a property ShowNodeToolTips that you can set to true and the TreeNodes have a ToolTipText property.

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However, if you want to display the ToolTip as a balloon, things get more complicated. Fortunately the TreeView has a NodeMouseHover event. Together with a Timer, we can make our ToolTip behave as expected.

In our form, we make these declarations and set the timer event handler

private const int InitialToolTipDelay = 500, MaxToolTipDisplayTime = 2000;

private ToolTip toolTip = new ToolTip();
private Timer timer = new Timer();
private TreeNode toolTipNode;

public frmTreeViewWithToolTip()
{
    InitializeComponent();
    toolTip.IsBalloon = true;
    timer.Tick += new EventHandler(timer_Tick);
}

In NodeMouseHover we initiate the process

private void treeView_NodeMouseHover(object sender,
                                     TreeNodeMouseHoverEventArgs e)
{
    timer.Stop();
    toolTip.Hide(this);

    toolTipNode = e.Node;

    timer.Interval = InitialToolTipDelay;
    timer.Start();
}

The timer will be started twice: once for the initial delay and once for maximum display time of the balloon. Therefore we must handle these two cases in the timer.Tick event handler

void timer_Tick(object sender, EventArgs e)
{
    timer.Stop();
    if (timer.Interval == InitialToolTipDelay) { 
        Point mousePos = treeView.PointToClient(MousePosition);

        // Show the ToolTip if the mouse is still over the same node.
        if (toolTipNode.Bounds.Contains(mousePos)) {
             // Node location in treeView coordinates.
            Point loc = toolTipNode.Bounds.Location;

             // Node location in form client coordinates.
            loc.Offset(treeView.Location);

            // Make balloon point to upper right corner of the node.
            loc.Offset(toolTipNode.Bounds.Width - 7, -12);

            toolTip.Show("Node: " + toolTipNode.Text, this, loc);

            timer.Interval = MaxToolTipDisplayTime;
            timer.Start();
        }
    } else {
        // Maximium ToolTip display time exceeded.
        toolTip.Hide(this);
    }
}

Finally, we do not want to display the ToolTip if the mouse leaves the TreeView

private void treeView_MouseLeave(object sender, EventArgs e)
{
    timer.Stop();
    toolTip.Hide(this);
}