Creating custom CompositeNode components

In this post we’ll examine how CompositeNode components work in MindFusion.Diagramming for Windows Forms, and in the process create a custom radio button component. You can find the completed sample project here:

CompositeNode was created as alternative of the ControlNode class, which lets you present any Windows Forms control as a diagram node. ControlNode has many advantages, such as letting you design the hosted user controls using Visual Studio designer, reusing them in other parts of the user interface, and including complex framework or third-party controls as their children. From the fact that each user control creates a hierarchy of Win32 windows come some disadvantages too:

  • ControlNodes cannot mix with other diagram elements in the Z order but are always drawn on top
  • performance deteriorates if showing hundreds of nodes
  • mouse events might not reach the diagram if hosted controls capture mouse input
  • print and export might not be able to reproduce the appearance of hosted controls without additional work (handling PaintControl event)

On the other hand, CompositeNode does all its drawing in DiagramView control’s canvas and is not affected by the issues listed above. CompositeNode lets you build node’s UI by composing hierarchy of components derived from ComponentBase class. Pre-defined components include layout panels, read-only or editable text fields, images, borders, buttons, check-boxes and sliders. If the UI component you need isn’t provided out of the box, you could still implement it as a custom class that derives from ComponentBase or more specific type and overriding the GetDesiredSize, ArrangeComponents and Draw methods. Lets see how that works using a RadioButtonComponent as an example.

Derive RadioButtonComponent from CheckBoxComponent so we reuse its IsChecked and Content properties:

class RadioButtonComponent : CheckBoxComponent

CompositeNode relies on a dynamic layout system that lets components determine their size by overriding GetDesiredSize method, and arranging children in allocated size by means of ArrangeComponents method. For radio button we’ll call its base class to measure content size and add enough space for drawing the radio graphics element (a circle) horizontally, while fitting it in measured height:

float RadioSize(SizeF size)
	return Math.Min(size.Width, size.Height);

public override SizeF GetDesiredSize(SizeF availableSize, IGraphics graphics)
	var s = base.GetDesiredSize(availableSize, graphics);
	s.Width += RadioSize(s);
	return s;

ArrangeComponents calls the base class to arrange its content on the right side of available space:

public override void ArrangeComponents(RectangleF availableSpace, IGraphics graphics)
	var radioSize = RadioSize(availableSpace.Size);
	availableSpace.X += radioSize;
	availableSpace.Width -= radioSize;
	base.ArrangeComponents(availableSpace, graphics);

Now override Draw and render standard radio button graphics on the left side of the component, and content on the right side:

public override void Draw(IGraphics graphics, RenderOptions options)
	var radioSize = RadioSize(Bounds.Size);
	var r = radioSize / 2 - 1;
	var cr = r - 1;

	graphics.FillEllipse(Brushes.White, Bounds.X + 1, Bounds.Y + 1, 2 * r, 2 * r);
	using (var pen = new System.Drawing.Pen(Color.Black, 0.1f))
		graphics.DrawEllipse(pen, Bounds.X + 1, Bounds.Y + 1, 2 * r, 2 * r);
	if (IsChecked)
		graphics.FillEllipse(Brushes.Black, Bounds.X + 2, Bounds.Y + 2, 2 * cr, 2 * cr);

	GraphicsState s = graphics.Save();
	graphics.TranslateTransform(radioSize - 1 + Bounds.X, Bounds.Y);
	Content.Draw(graphics, options);

We’ll want only one radio from a group to be selected. For our purposes we can count all radio buttons placed inside same stack panel as part of same group. Override the OnClick method to unselect all buttons in parent panel and select the clicked one:

protected override void OnClicked(EventArgs e)
	var parentStack = Parent as StackPanel;
	if (parentStack != null)
		foreach (var child in parentStack.Components)
			var radio = child as RadioButtonComponent;
			if (radio != null)
				radio.IsChecked = false;
	this.IsChecked = true;

That’s it, the radio button component is ready with just a screenful of code 🙂 Let’s check how it works by creating an OptionNode class that shows a group of radio buttons and exposes a property to access or change selected one:

class OptionNode : CompositeNode

You could create the stack panel and radio buttons from code if you need more dynamic configuration, e.g. one with variable number of radio buttons. For this example we’ll just load a fixed template consisting of four buttons from XML:

const string Template = @"

        <Shape Name=""Shape"" Shape=""RoundRect"" />

		<Border Padding=""2"">

			<StackPanel Name=""RadioGroup""
				Orientation=""Vertical"" Spacing=""1"" HorizontalAlignment=""Center"">
				<RadioButtonComponent Padding=""2"">
						<Text Text=""option 1"" Font=""Verdana, 3world, style=Bold"" />
				<RadioButtonComponent Padding=""2"">
						<Text Text=""option 2"" Font=""Verdana, 3world, style=Bold"" />
				<RadioButtonComponent Padding=""2"">
						<Text Text=""option 3"" Font=""Verdana, 3world, style=Bold"" />
				<RadioButtonComponent Padding=""2"">
						<Text Text=""option 4"" Font=""Verdana, 3world, style=Bold"" />



The template can be loaded using the XmlLoader class. We’ll also store a reference to the stack panel so we can access its child radio buttons:

public OptionNode()

public OptionNode(Diagram d)
	: base(d)

private void Load()
	Components.Add(XmlLoader.Load(Template, this, null));

	radioGroup = FindComponent("RadioGroup") as StackPanel;

StackPanel radioGroup;

Now implement a SelectedOption property that lets us select a radio button by its index. Define it as nullable integer so we can represent missing select too:

public int? SelectedOption
		for (int i = 0; i < radioGroup.Components.Count; i++)
			var radioButton = (RadioButtonComponent)radioGroup.Components[i];
			if (radioButton.IsChecked)
				return i;
		return null;
		for (int i = 0; i < radioGroup.Components.Count; i++)
			var radioButton = (RadioButtonComponent)radioGroup.Components[i];
			radioButton.IsChecked = value == i;

Let’s try it – create a few nodes and run the application, you’ll see the screen shown below:

var node1 = new OptionNode();
node1.Bounds = new RectangleF(20, 20, 30, 40);
node1.SelectedOption = 0;

var node2 = new OptionNode();
node2.Bounds = new RectangleF(90, 20, 30, 40);
node2.SelectedOption = 1;

var node3 = new OptionNode();
node3.Bounds = new RectangleF(20, 80, 30, 40);
node3.SelectedOption = null;

var node4 = new OptionNode();
node4.Bounds = new RectangleF(90, 80, 30, 40);
node4.SelectedOption = 3;

for (int i = 0; i < diagram.Nodes.Count - 1; i++)
		diagram.Nodes[i], diagram.Nodes[i + 1]);

Radio buttons in MindFusion diagram nodes

To be fair, this kind of nodes is simple enough to implement using standard TableNode class where radio button graphics are either custom drawn or set as Image inside table cells in first column, and text displayed in second column. However the radio buttons can be mixed with other components in CompositeNodes to implement more complex user interfaces than ones possible with tables.

For more information on MindFusion flow diagramming libraries for various desktop, web and mobile platforms, see MindFusion.Diagramming Pack page.


Layout Management with the WinForms Dock Control

In this post we will show you how to build a sample application with customizable layout based on the WinForms Dock control, which is part of MindFusion WinForms pack. You can find further details about the control at its web page.

For the purpose of the demonstration we’ve chosen an entertaining topic – a cooking recipes electronic book. Our book so far has only three recipes, all for sweets. Lets start by looking at the

I. Architecture of the sample.

The sample has two custom classes – Ingredient and Recipe. Each Ingredient has quantity, name and an image, which illustrates it. The Recipe class holds a strongly typed list with Ingredient objects, the title for each recipe, an image for the recipe, an icon for the recipe and preparation instructions.

The application consists of the dock control, which contains four DockItem-s : for the recipes, for their images, for their ingredients and with the preparation instructions. Any dock item can be dragged, dropped, aligned, minimized, hidden etc.

The API of the cook book application

The API of the cook book application

II. The Dock Control.

We create an empty WinForms project and add the Dock control from the toolbox. The dock control fills the entire client area:

this.dockControl1.Dock = System.Windows.Forms.DockStyle.Fill;         
this.dockControl1.Location = new System.Drawing.Point(0, 0);           
this.dockControl1.Size = new System.Drawing.Size(784, 562);

These properties are set in the Property grid.

Each dock item is created with a title and id, which helps us identify it.

titleItem = new DockItem() { Header = "Recipe Name", Id = "Name" };
titleItem.DockStyle = DockStyle.Left;      
titleItem.Content = GetContent("Name");

The DockStyle property is responsible for the initial layout of the dock item. You can choose among various dock styles – fill, bottom, top and more.

The GetContent method is very important. It prepares the controls that will be placed into each dock item and returns the appropriate one according to the parameter.

Once the dock item is created, let’s not forget to add it:


III. Creating the Content.

Let’s see how the content for a dock item is created. Let’s take the grid with the ingredients. It is identified with the “Ingredients” id:

private Control GetContent(string contentType)
  Control control = null;
  else if (contentType == "Ingredients")
             grid = new DataGridView();
             grid.DefaultCellStyle.BackColor = Color.FromArgb(247, 226, 189);
             grid.Dock = DockStyle.Fill;
             grid.MultiSelect = false;
             grid.DataSource = selectedRecipe.Ingredients;
             grid.RowTemplate.MinimumHeight = 35;
             grid.RowHeadersWidthSizeMode =
             grid.ColumnHeadersHeightSizeMode = DataGridViewColumnHeadersHeightSizeMode.DisableResizing;
             grid.AutoSizeColumnsMode = DataGridViewAutoSizeColumnsMode.Fill;
             grid.SelectionMode = DataGridViewSelectionMode.FullRowSelect;
             grid.BackgroundColor = Color.FromArgb(253, 244, 247);

             control = grid; 
return control;

The idea is clear: you create the control, which will be rendered in the dock item and assign it to DockItem.Content. Here we make different customization for the grid – we change the color of table rows, adjust the height, turn off multiple row select and more.

IV. Changing the Content.

We change the content by handling the SelectedIndexChanged event for the ListView, which lists our recipes. When the user selects a new list item, we extract its Recipe and change the content of the other DockItem-s:

selectedRecipe = recipes[recipesListView.SelectedIndices[0]];
tb.Text = selectedRecipe.Preparation;
grid.DataSource = selectedRecipe.Ingredients;
pictureBox.Image = Image.FromFile(selectedRecipe.ImageUrl);

Here is the final output of the sample application:

MindFusion WinForms Dock COntrol

A Sample electronic cook book based on MindFusion WinForms Dock Control

You can download the sample directly from this link:

MindFusion WinForms Layout Control Sample: Electronic Cook Book in C#

MindFusion WinForms Layout Control Sample: Electronic Cook Book in VB.NET

Enjoy the fast, easy and straight-forwarded manner in which you can create a WinForms application with a flexible layout and multiple panels.