I have a mesh system for a MMO and it's uses A* to find paths. Occasionally it fails because I have nodes that are badly placed. To fix this, I made a mesh visualiser. It works OKish - I can see that some nodes are badly placed. But I can't see which nodes.

Here is my code to show the nodes:

    foreach (var node in FormMap.Nodes)
    {

        var x1 = (node.Point.X * sideX);
        var y1 = (node.Point.Y * sideY);

        var x = x1 - nodeWidth / 2;
        var y = y1 - nodeWidth / 2;

        var brs = Brushes.Black;
        //if (node.Visited)
        //    brs = Brushes.Red;
        if (node == FormMap.StartNode)
            brs = Brushes.DarkOrange;
        if (node == FormMap.EndNode)
            brs = Brushes.Green;
        g.FillEllipse(brs, (float)x, (float)y, nodeWidth, nodeWidth);

I know I can redo this and make thousands of small buttons and add events for them but that seems overkill.

Is there any way I can add tooltips to the nodes I am painting on the panel?

CodePudding user response：

Yes, you can show a tooltip for your nodes that you have drawn on the drawing surface. To do so, you need to do the followings:

• Implement hit-testing for your node, so you can get the node under the mouse position.
• Create a timer and In mouse move event handler of the drawing surface, do hit-testing to find the hot item. If the hot node is not same as the current hot node, you stop the timer, otherwise, if there's a new hot item you start the timer.
• In the timer tick event handler, check if there's a hot item, show the tooltip and stop the time.
• In the mouse leave event of the drawing surface, stop the timer.

And here is the result, which shows tooltip for some points in a drawing:

The above algorithm, is being used in internal logic of ToolStrip control to show tooltip for the tool strip items (which are not control). So without wasting a lot of windows handle, and using a single parent control and a single tooltip, you can show tooltip for as many nodes as you want.

Code Example - Show Tooltip for some points in a drawing

Here is the drawing surface:

using System.ComponentModel;
using System.Drawing.Drawing2D;
public class DrawingSurface : Control
{
    [DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
    [Browsable(false)]
    public List<Node> Nodes { get; }
    public DrawingSurface()
    {
        Nodes = new List<Node>();
        ResizeRedraw = true;
        DoubleBuffered = true;
        toolTip = new ToolTip();
        mouseHoverTimer = new System.Windows.Forms.Timer();
        mouseHoverTimer.Enabled = false;
        mouseHoverTimer.Interval = SystemInformation.MouseHoverTime;
        mouseHoverTimer.Tick  = mouseHoverTimer_Tick;
    }
    private void mouseHoverTimer_Tick(object sender, EventArgs e)
    {
        mouseHoverTimer.Enabled = false;
        if (hotNode != null)
        {
            var p = hotNode.Location;
            p.Offset(16, 16);
            toolTip.Show(hotNode.Name, this, p, 2000);
        }
    }

    private System.Windows.Forms.Timer mouseHoverTimer;
    private ToolTip toolTip;
    Node hotNode;
    protected override void onm ouseMove(MouseEventArgs e)
    {
        base.OnMouseMove(e);
        var node = Nodes.Where(x => x.HitTest(e.Location)).FirstOrDefault();
        if (node != hotNode)
        {
            mouseHoverTimer.Enabled = false;
            toolTip.Hide(this);
        }
        hotNode = node;
        if (node != null)
            mouseHoverTimer.Enabled = true;
        Invalidate();
    }
    protected override void onm ouseLeave(EventArgs e)
    {
        base.OnMouseLeave(e);
        hotNode = null;
        mouseHoverTimer.Enabled = false;
        Invalidate();
    }
    protected override void OnPaint(PaintEventArgs e)
    {
        base.OnPaint(e);
        e.Graphics.SmoothingMode = SmoothingMode.AntiAlias;
        if (Nodes.Count >= 2)
            e.Graphics.DrawLines(Pens.Black,
            Nodes.Select(x => x.Location).ToArray());
        foreach (var node in Nodes)
            node.Draw(e.Graphics, node == hotNode);
    }
    protected override void Dispose(bool disposing)
    {
        if (disposing)
        {
            if (mouseHoverTimer != null)
            {
                mouseHoverTimer.Enabled = false;
                mouseHoverTimer.Dispose();
            }
            if (toolTip != null)
            {
                toolTip.Dispose();
            }
        }
        base.Dispose(disposing);
    }
}

Here is the node class:

using System.Drawing.Drawing2D;
public class Node
{
    int NodeWidth = 16;
    Color NodeColor = Color.Blue;
    Color HotColor = Color.Red;
    public string Name { get; set; }
    public Point Location { get; set; }
    private GraphicsPath GetShape()
    {
        GraphicsPath shape = new GraphicsPath();
        shape.AddEllipse(Location.X - NodeWidth / 2, Location.Y - NodeWidth / 2,
            NodeWidth, NodeWidth);
        return shape;
    }
    public void Draw(Graphics g, bool isHot = false)
    {
        using (var brush = new SolidBrush(isHot ? HotColor : NodeColor))
        using (var shape = GetShape())
        {
            g.FillPath(brush, shape);
        }
    }
    public bool HitTest(Point p)
    {
        using (var shape = GetShape())
            return shape.IsVisible(p);
    }
}

And here is the example form, which has a drawing surface control on it:

protected override void onl oad(EventArgs e)
{
    base.OnLoad(e);
    drawingSurface1.Nodes.Add(new Node() { 
        Name = "Node1", Location = new Point(100, 100) });
    drawingSurface1.Nodes.Add(new Node() { 
        Name = "Node2", Location = new Point(150, 70) });
    drawingSurface1.Nodes.Add(new Node() { 
        Name = "Node3", Location = new Point(170, 140) });
    drawingSurface1.Nodes.Add(new Node() { 
        Name = "Node4", Location = new Point(200, 50) });
    drawingSurface1.Nodes.Add(new Node() { 
        Name = "Node5", Location = new Point(90, 160) });
    drawingSurface1.Invalidate();
}