Question

I don’t understand why I can’t bind my custom width dependency property (of my custom control) to another custom control dependency property.

I followed all guidelines I’m quite sure dependency properties are well implemented.

Both Window (BlackAndWhiteWindow), Canvas (all of them are custom controls, not those from wpf) inherits from control.

Any suggestion? I’m going mad…

Visual studio error states that is impossible to bind the property because you can only bind a dependency property to a dependency object, but they are dependency objects and i’m binding to dependency properties!!

EDIT 1:

XAML

<test:BlackAndWhiteWindow x:Class="GSdk.TestGsdkShared.TestWindow" x:Name="bwWindow"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
             xmlns:windows="urn:gsdk-net"
             xmlns:test="clr-namespace:GSdk.TestGsdkShared"
             mc:Ignorable="d"
             Width="320" Height="240"
             d:DesignHeight="300" d:DesignWidth="300">
    <windows:Canvas Width="{Binding ElementName=bwWindow, Path=Width}" Height="100">
    </windows:Canvas>
</test:BlackAndWhiteWindow>

Control class

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Drawing;
using GSdk.Net.Lglcd;
using System.Windows;
using System.Windows.Markup;
using System.Xaml;
using GSdk.Shared.Windows.Properties;

namespace GSdk.Shared.Windows
{
    public class Control : DependencyObject, IDisposable
    {
        private volatile bool m_Disposing;

        public Control()
        {
            /*Font = new Font(
                "monospace",
                12.0f,
                System.Drawing.FontStyle.Bold
            );*/
        }

        public static Property<Font> FontProperty = new Property<ContentControl, Font>(c => c.Font, new FrameworkPropertyMetadata(new Font("monospace", 12.0f, System.Drawing.FontStyle.Bold), FrameworkPropertyMetadataOptions.Inherits));
        public static Property<int> WidthProperty = new Property<ContentControl, int>(c => c.Width, new FrameworkPropertyMetadata(1, FrameworkPropertyMetadataOptions.Inherits));
        public static Property<int> HeightProperty = new Property<ContentControl, int>(c => c.Height, new FrameworkPropertyMetadata(1, FrameworkPropertyMetadataOptions.Inherits));

        public Font Font
        {
            get { return FontProperty[this]; }
            set
            {
                if (Font != null && Font != value)
                    Font.Dispose();
                FontProperty[this] = value;
            }
        }
        public int Width { get { return WidthProperty[this]; } set { WidthProperty[this] = value; } }
        public int Height { get { return HeightProperty[this]; } set { HeightProperty[this] = value; } }
        public virtual DeviceTypes DeviceType { get { return DeviceTypes.Invalid; } }
        public bool Disposing { get { return m_Disposing; } protected set { m_Disposing = value; } }

        #region Dispose handling
        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        protected virtual void Dispose(bool disposing)
        {
            Disposing = true;
            if (disposing)
            {
                // Managed resources
            }

            // Unmanaged resources
            try
            {
                if (Font != null) Font.Dispose();
            }
            catch { }
        }

        ~Control()
        {
            Dispose(false);
        }
        #endregion
    }
}

Canvas class

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Drawing;
using GSdk.Net.Lglcd;
using System.Windows;
using System.Windows.Markup;
using System.Xaml;
using GSdk.Shared.Windows.Properties;

namespace GSdk.Shared.Windows
{
    public class Canvas : Layout, IDrawable
    {
        public Canvas()
            : base()
        {
        }

        public static Property<int> TopProperty = new AttachedProperty<Canvas, int>(() => TopProperty, new FrameworkPropertyMetadata(default(int), FrameworkPropertyMetadataOptions.Inherits));
        public static Property<int> LeftProperty = new AttachedProperty<Canvas, int>(() => LeftProperty, new FrameworkPropertyMetadata(default(int), FrameworkPropertyMetadataOptions.Inherits));
        public static Property<int> BottomProperty = new AttachedProperty<Canvas, int>(() => BottomProperty, new FrameworkPropertyMetadata(default(int), FrameworkPropertyMetadataOptions.Inherits));
        public static Property<int> RightProperty = new AttachedProperty<Canvas, int>(() => RightProperty, new FrameworkPropertyMetadata(default(int), FrameworkPropertyMetadataOptions.Inherits));

        public static void SetTop(DependencyObject obj, int value)
        {
            obj.SetValue(TopProperty, value);
        }
        public static int GetTop(DependencyObject obj)
        {
            return (int)obj.GetValue(TopProperty);
        }
        public static bool IsSetTop(DependencyObject obj)
        {
            return ((int)obj.GetValue(TopProperty) != default(int));
        }

        public static void SetLeft(DependencyObject obj, int value)
        {
            obj.SetValue(LeftProperty, value);
        }
        public static int GetLeft(DependencyObject obj)
        {
            return (int)obj.GetValue(LeftProperty);
        }
        public static bool IsSetLeft(DependencyObject obj)
        {
            return ((int)obj.GetValue(LeftProperty) != default(int));
        }

        public static void SetBottom(DependencyObject obj, int value)
        {
            obj.SetValue(BottomProperty, value);
        }
        public static int GetBottom(DependencyObject obj)
        {
            return (int)obj.GetValue(BottomProperty);
        }
        public static bool IsSetBottom(DependencyObject obj)
        {
            return ((int)obj.GetValue(BottomProperty) != default(int));
        }

        public static void SetRight(DependencyObject obj, int value)
        {
            obj.SetValue(RightProperty, value);
        }
        public static int GetRight(DependencyObject obj)
        {
            return (int)obj.GetValue(RightProperty);
        }
        public static bool IsSetRight(DependencyObject obj)
        {
            return ((int)obj.GetValue(RightProperty) != default(int));
        }

        public Bitmap Draw()
        {
            // FIXME: This should be changed, is temporary
            //MessageBox.Show(Width.ToString() + " " + Height.ToString());
            Bitmap tmp = new Bitmap(Width, Height);
            using (Graphics g = Graphics.FromImage(tmp))
            {
                g.FillRectangle(Brushes.AliceBlue, 0, 0, Width, Height);
                foreach (var item in Items)
                {
                    int x, y;
                    x = y = 0;
                    IDrawable drawableItem = item as IDrawable;
                    DependencyObject dependencyItem = item as DependencyObject;

                    if (dependencyItem != null && drawableItem != null)
                    {
                        if (IsSetTop(dependencyItem))
                            y = GetTop(dependencyItem);
                        else if (IsSetBottom(dependencyItem))
                            y = Height - GetBottom(dependencyItem);

                        if (IsSetLeft(dependencyItem))
                            x = GetLeft(dependencyItem);
                        else if (IsSetRight(dependencyItem))
                            x = Width - GetRight(dependencyItem);
                        g.DrawImage(drawableItem.Draw(), x, y);
                    }
                }
            }
            return tmp;
        }
    }
}

Window class

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Drawing;
using GSdk.Net.Lglcd;
using System.Windows;
using System.Windows.Markup;
using System.Xaml;
using GSdk.Shared.Windows.Properties;
using System.ComponentModel;
using System.Reflection;
using System.Threading;
using System.Threading.Tasks;

namespace GSdk.Shared.Windows
{
    public abstract class Window : ContentControl, IDrawable
    {
        private Action m_DispatcherDrawHandler;
        private Thread m_DrawThread;
        private Bitmap Background = QvgaDevice.CreateValidBitmap();

        public Window(Applet applet = null)
        {
            m_DispatcherDrawHandler = new Action(DispatcherDrawHandler);
            if (DesignerProperties.GetIsInDesignMode(this))
            {
                Applet = new Applet()
                {
                    Autostartable = false,
                    SupportedDevices = DeviceType,
                    Name = GetType().FullName,
                };
                Applet.Connect();
                Applet.GetDevices<DefaultDeviceCollection>().Qvga.ForegroundApplet = true;
                Applet.GetDevices<DefaultDeviceCollection>().Qvga.AppletPriority = AppletPriorities.Alert;

                m_DrawThread = new Thread(new ThreadStart(DrawHandler));
                m_DrawThread.Start();
                //Dispatcher.Hooks.DispatcherInactive += new EventHandler(Hooks_DispatcherInactive);
            }
            else
            {
                Applet = applet ?? CreateApplet();
                //if (Applet == null) throw new NullReferenceException("CreateApplet() must return a not null value");
            }
        }

        private void DispatcherDrawHandler()
        {
            Applet.GetDevices<DefaultDeviceCollection>().Qvga.Update(Draw());
        }

        private void DrawHandler()
        {
            while (!Disposing)
            {
                Dispatcher.Invoke(m_DispatcherDrawHandler);
                Thread.Sleep(33);
            }
        }

        /*private void Hooks_DispatcherInactive(object sender, EventArgs e)
        {
            Dispatcher.Invoke(new Action(() =>
            {
            }));
        }*/

        protected abstract Applet CreateApplet();

        //public readonly object SyncRoot = new object();
        public Applet Applet { get; private set; }
        public override DeviceTypes DeviceType { get { return DeviceTypes.Qvga; } }

        public virtual Bitmap Draw()
        {
            using (Graphics g = Graphics.FromImage(Background))
            {
                g.FillRectangle(Brushes.Red, new Rectangle(0, 0, Background.Width, Background.Height));
                g.DrawString("Hello World", Font, Brushes.White, new PointF(0f, 0f));

                IDrawable ctrl = Content as IDrawable;
                if (ctrl != null)
                    g.DrawImage(ctrl.Draw(), 0, 0);
            }
            return Background;
        }

        protected override void Dispose(bool disposing)
        {
            base.Dispose(disposing);
            lock (Applet)
                if (Applet != null) Applet.Dispose();
        }
    }
}

Property class

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Linq.Expressions;
using System.Windows;

namespace GSdk.Shared.Windows.Properties
{
    public struct Property<T>
    {
        Property(DependencyProperty prop)
        {
            m_DependencyProperty = prop;
        }

        readonly DependencyProperty m_DependencyProperty;

        public static implicit operator Property<T>(PropertyBase prop)
        {
            return new Property<T>(prop.DependencyProperty);
        }

        public static implicit operator DependencyProperty(Property<T> prop)
        {
            return prop.m_DependencyProperty;
        }

        public T this[DependencyObject obj]
        {
            get { return (T)obj.GetValue(m_DependencyProperty); }
            set { obj.SetValue(m_DependencyProperty, value); }
        }
    }

    public abstract class PropertyBase
    {
        public readonly DependencyProperty DependencyProperty;

        protected PropertyBase(DependencyProperty prop)
        {
            DependencyProperty = prop;
        }
    }

    public sealed class Property<TContainer, TValue> : PropertyBase
    {
        public Property(Expression<Func<TContainer, TValue>> accessor)
            : base(DependencyProperty.Register(accessor.MemberToString(), typeof(TValue), typeof(TContainer)))
        {
        }
        public Property(Expression<Func<TContainer, TValue>> accessor, PropertyMetadata metadata)
            : base(DependencyProperty.Register(accessor.MemberToString(), typeof(TValue), typeof(TContainer), metadata))
        {
        }
        public Property(Expression<Func<TContainer, TValue>> accessor, PropertyMetadata metadata, ValidateValueCallback callback)
            : base(DependencyProperty.Register(accessor.MemberToString(), typeof(TValue), typeof(TContainer), metadata, callback))
        {
        }
    }

    public sealed class AttachedProperty<TContainer, TValue> : PropertyBase
    {
        public AttachedProperty(Expression<Func<Property<TValue>>> accessor)
            : base(DependencyProperty.RegisterAttached(accessor.MemberToString().Substring(0,accessor.MemberToString().Length - "Property".Length), typeof(TValue), typeof(TContainer)))
        {
        }
        public AttachedProperty(Expression<Func<Property<TValue>>> accessor, PropertyMetadata metadata)
            : base(DependencyProperty.RegisterAttached(accessor.MemberToString().Substring(0, accessor.MemberToString().Length - "Property".Length), typeof(TValue), typeof(TContainer), metadata))
        {
        }
        public AttachedProperty(Expression<Func<Property<TValue>>> accessor, PropertyMetadata metadata, ValidateValueCallback callback)
            : base(DependencyProperty.RegisterAttached(accessor.MemberToString().Substring(0, accessor.MemberToString().Length - "Property".Length), typeof(TValue), typeof(TContainer), metadata, callback))
        {
        }
    }
}

Answer 1

The problem seems that it’s connected to the fact that I’m using a class that is emulating a dependencyproperty (the property struct), while it’s not directly a dependency property. Solved by using the normal dependency property