GtkSharp/sample/PolarFixed.cs

// This is a completely pointless widget, but it shows how to subclass container...

using System;
using System.Collections;
using Gtk;
using Gdk;

class PolarFixed : Container {
	ArrayList children;

	public PolarFixed ()
	{
		children = new ArrayList ();
		WidgetFlags |= WidgetFlags.NoWindow;
	}

	// The child properties object
	public class PolarFixedChild : ContainerChild {
		double theta;
		uint r;

		public PolarFixedChild (PolarFixed parent, Widget child, double theta, uint r) : base (parent, child)
		{
			this.theta = theta;
			this.r = r;
		}

		// We call parent.QueueResize() from the property setters here so that you
		// can move the widget around just by changing its child properties (just
		// like with a native container class).

		public double Theta {
			get { return theta; }
			set {
				theta = value;
				parent.QueueResize ();
			}
		}

		public uint R {
			get { return r; }
			set {
				r = value;
				parent.QueueResize ();
			}
		}
	}

	// Override the child properties accessor to return the right object from
	// "children".
	public override ContainerChild this [Widget w] {
		get {
			foreach (PolarFixedChild pfc in children) {
				if (pfc.Child == w)
					return pfc;
			}
			return null;
		}
	}

	// Indicate the kind of children the container will accept. Most containers
	// will accept any kind of child, so they should return Gtk.Widget.GType.
	// The default is "GLib.GType.None", which technically means that no (new)
	// children can be added to the container, though Container.Add does not
	// enforce this.
	public override GLib.GType ChildType ()
	{
		return Gtk.Widget.GType;
	}

	// Implement gtk_container_forall(), which is also used by
	// Gtk.Container.Children and Gtk.Container.AllChildren.
	protected override void ForAll (bool include_internals, Callback callback)
	{
		foreach (PolarFixedChild pfc in children)
			callback (pfc.Child);
	}

	// Invoked by Container.Add (w). It's good practice to have this do *something*,
	// even if it's not something terribly useful.
	protected override void OnAdded (Widget w)
	{
		Put (w, 0.0, 0);
	}

	// our own adder method
	public void Put (Widget w, double theta, uint r)
	{
		children.Add (new PolarFixedChild (this, w, theta, r));
		w.Parent = this;
		QueueResize ();
	}

	public void Move (Widget w, double theta, uint r)
	{
		PolarFixedChild pfc = (PolarFixedChild)this[w];
		if (pfc != null) {
			pfc.Theta = theta;
			pfc.R = r;
		}
	}

	// invoked by Container.Remove (w)
	protected override void OnRemoved (Widget w)
	{
		PolarFixedChild pfc = (PolarFixedChild)this[w];
		if (pfc != null) {
			pfc.Child.Unparent ();
			children.Remove (pfc);
			QueueResize ();
		}
	}

	// Handle size request
	protected override void OnSizeRequested (ref Requisition req)
	{
		Requisition childReq;
		int x, y;

		req.Width = req.Height = 0;
		foreach (PolarFixedChild pfc in children) {
			// Recursively SizeRequest each child
			childReq = pfc.Child.SizeRequest ();

			// Figure out where we're going to put it
			x = (int)(Math.Cos (pfc.Theta) * pfc.R) + childReq.Width / 2;
			y = (int)(Math.Sin (pfc.Theta) * pfc.R) + childReq.Height / 2;

			// Update our own size request to fit it
			if (req.Width < 2 * x)
				req.Width = 2 * x;
			if (req.Height < 2 * y)
				req.Height = 2 * y;
		}

		// Take Container.BorderWidth into account
		req.Width += (int)(2 * BorderWidth);
		req.Height += (int)(2 * BorderWidth);
	}

	// Size allocation. Note that the allocation received may be smaller than what we
	// requested. Some containers will take that into account by giving some or all
	// of their children a smaller allocation than they requested. Other containers
	// (like this one) just let their children get placed partly out-of-bounds if they
	// aren't allocated enough room.
	protected override void OnSizeAllocated (Rectangle allocation)
	{
		Requisition childReq;
		int cx, cy, x, y;

		// This sets the "Allocation" property. For widgets that
		// have a GdkWindow, it also calls GdkWindow.MoveResize()
		base.OnSizeAllocated (allocation);

		// Figure out where the center of the grid will be
		cx = allocation.X + (allocation.Width / 2);
		cy = allocation.Y + (allocation.Height / 2);

		foreach (PolarFixedChild pfc in children) {
			// Use ChildRequisition rather than SizeRequest(),
			// to ask for "what this child requested in the
			// last SizeRequest", rather than having it
			// compute it anew.
			childReq = pfc.Child.ChildRequisition;

			x = (int)(Math.Cos (pfc.Theta) * pfc.R) - childReq.Width / 2;
			y = (int)(Math.Sin (pfc.Theta) * pfc.R) + childReq.Height / 2;

			allocation.X = cx + x;
			allocation.Width = childReq.Width;
			allocation.Y = cy - y;
			allocation.Height = childReq.Height;

			pfc.Child.Allocation = allocation;
		}
	}
}

class Test {
	public static void Main ()
	{
		uint r;
		double theta;

		Application.Init ();

		Gtk.Window win = new Gtk.Window ("Polar Coordinate Container");
		win.DeleteEvent += Window_Delete;

		Notebook notebook = new Notebook ();
		win.Add (notebook);

		// Clock
		PolarFixed pf = new PolarFixed ();
		notebook.AppendPage (pf, new Label ("Clock"));

		for (int hour = 1; hour <= 12; hour ++) {
			theta = (Math.PI / 2) - hour * (Math.PI / 6);
			if (theta < 0)
				theta += 2 * Math.PI;

			Label l = new Label ("<big><b>" + hour.ToString () + "</b></big>");
			l.UseMarkup = true;
			pf.Put (l, theta, 200);
		}

		// Spiral
		pf = new PolarFixed ();
		notebook.AppendPage (pf, new Label ("Spiral"));

		r = 0;
		theta = 0.0;

		foreach (string id in Gtk.Stock.ListIds ()) {
			StockItem item = Gtk.Stock.Lookup (id);
			if (item.Label == null)
				continue;

			pf.Put (new Gtk.Button (id), theta, r);

			// Logarithmic spiral: r = a*e^(b*theta)
			r += 5;
			theta = 10 * Math.Log (10 * r);
		}

		win.ShowAll ();

		Application.Run ();
	}

	static void Window_Delete (object obj, DeleteEventArgs args)
	{
		Application.Quit ();
		args.RetVal = true;
	}
}