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ReversiEight - A Windows 8 Reversi Game

, 22 May 2013
Describes the development of a Windows 8 Reversi game, covering the topics of UI design, the minimax algorithm and an interesting use for Linq.
ReversiEight.zip
ReversiEight
Assets
Background.jpg
BlackPiece.png
Board.png
GameOver.png
Logo.png
ReversiText.png
SmallLogo.png
SplashScreen.png
StoreLogo.png
WhitePiece.png
Common
Converters
Package.appxmanifest
Properties
ReversiEight_TemporaryKey.pfx
ViewModel
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using Windows.Foundation;
using Windows.Foundation.Collections;
using Windows.System;
using Windows.UI.Core;
using Windows.UI.ViewManagement;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Navigation;

namespace ReversiEight.Common
{
    /// <summary>
    /// Typical implementation of Page that provides several important conveniences:
    /// <list type="bullet">
    /// <item>
    /// <description>Application view state to visual state mapping</description>
    /// </item>
    /// <item>
    /// <description>GoBack, GoForward, and GoHome event handlers</description>
    /// </item>
    /// <item>
    /// <description>Mouse and keyboard shortcuts for navigation</description>
    /// </item>
    /// <item>
    /// <description>State management for navigation and process lifetime management</description>
    /// </item>
    /// <item>
    /// <description>A default view model</description>
    /// </item>
    /// </list>
    /// </summary>
    [Windows.Foundation.Metadata.WebHostHidden]
    public class LayoutAwarePage : Page
    {
        /// <summary>
        /// Identifies the <see cref="DefaultViewModel"/> dependency property.
        /// </summary>
        public static readonly DependencyProperty DefaultViewModelProperty =
            DependencyProperty.Register("DefaultViewModel", typeof(IObservableMap<String, Object>),
            typeof(LayoutAwarePage), null);

        private List<Control> _layoutAwareControls;

        /// <summary>
        /// Initializes a new instance of the <see cref="LayoutAwarePage"/> class.
        /// </summary>
        public LayoutAwarePage()
        {
            if (Windows.ApplicationModel.DesignMode.DesignModeEnabled) return;

            // Create an empty default view model
            this.DefaultViewModel = new ObservableDictionary<String, Object>();

            // When this page is part of the visual tree make two changes:
            // 1) Map application view state to visual state for the page
            // 2) Handle keyboard and mouse navigation requests
            this.Loaded += (sender, e) =>
            {
                this.StartLayoutUpdates(sender, e);

                // Keyboard and mouse navigation only apply when occupying the entire window
                if (this.ActualHeight == Window.Current.Bounds.Height &&
                    this.ActualWidth == Window.Current.Bounds.Width)
                {
                    // Listen to the window directly so focus isn't required
                    Window.Current.CoreWindow.Dispatcher.AcceleratorKeyActivated +=
                        CoreDispatcher_AcceleratorKeyActivated;
                    Window.Current.CoreWindow.PointerPressed +=
                        this.CoreWindow_PointerPressed;
                }
            };

            // Undo the same changes when the page is no longer visible
            this.Unloaded += (sender, e) =>
            {
                this.StopLayoutUpdates(sender, e);
                Window.Current.CoreWindow.Dispatcher.AcceleratorKeyActivated -=
                    CoreDispatcher_AcceleratorKeyActivated;
                Window.Current.CoreWindow.PointerPressed -=
                    this.CoreWindow_PointerPressed;
            };
        }

        /// <summary>
        /// An implementation of <see cref="IObservableMap&lt;String, Object&gt;"/> designed to be
        /// used as a trivial view model.
        /// </summary>
        protected IObservableMap<String, Object> DefaultViewModel
        {
            get
            {
                return this.GetValue(DefaultViewModelProperty) as IObservableMap<String, Object>;
            }

            set
            {
                this.SetValue(DefaultViewModelProperty, value);
            }
        }

        #region Navigation support

        /// <summary>
        /// Invoked as an event handler to navigate backward in the page's associated
        /// <see cref="Frame"/> until it reaches the top of the navigation stack.
        /// </summary>
        /// <param name="sender">Instance that triggered the event.</param>
        /// <param name="e">Event data describing the conditions that led to the event.</param>
        protected virtual void GoHome(object sender, RoutedEventArgs e)
        {
            // Use the navigation frame to return to the topmost page
            if (this.Frame != null)
            {
                while (this.Frame.CanGoBack) this.Frame.GoBack();
            }
        }

        /// <summary>
        /// Invoked as an event handler to navigate backward in the navigation stack
        /// associated with this page's <see cref="Frame"/>.
        /// </summary>
        /// <param name="sender">Instance that triggered the event.</param>
        /// <param name="e">Event data describing the conditions that led to the
        /// event.</param>
        protected virtual void GoBack(object sender, RoutedEventArgs e)
        {
            // Use the navigation frame to return to the previous page
            if (this.Frame != null && this.Frame.CanGoBack) this.Frame.GoBack();
        }

        /// <summary>
        /// Invoked as an event handler to navigate forward in the navigation stack
        /// associated with this page's <see cref="Frame"/>.
        /// </summary>
        /// <param name="sender">Instance that triggered the event.</param>
        /// <param name="e">Event data describing the conditions that led to the
        /// event.</param>
        protected virtual void GoForward(object sender, RoutedEventArgs e)
        {
            // Use the navigation frame to move to the next page
            if (this.Frame != null && this.Frame.CanGoForward) this.Frame.GoForward();
        }

        /// <summary>
        /// Invoked on every keystroke, including system keys such as Alt key combinations, when
        /// this page is active and occupies the entire window.  Used to detect keyboard navigation
        /// between pages even when the page itself doesn't have focus.
        /// </summary>
        /// <param name="sender">Instance that triggered the event.</param>
        /// <param name="args">Event data describing the conditions that led to the event.</param>
        private void CoreDispatcher_AcceleratorKeyActivated(CoreDispatcher sender,
            AcceleratorKeyEventArgs args)
        {
            var virtualKey = args.VirtualKey;

            // Only investigate further when Left, Right, or the dedicated Previous or Next keys
            // are pressed
            if ((args.EventType == CoreAcceleratorKeyEventType.SystemKeyDown ||
                args.EventType == CoreAcceleratorKeyEventType.KeyDown) &&
                (virtualKey == VirtualKey.Left || virtualKey == VirtualKey.Right ||
                (int)virtualKey == 166 || (int)virtualKey == 167))
            {
                var coreWindow = Window.Current.CoreWindow;
                var downState = CoreVirtualKeyStates.Down;
                bool menuKey = (coreWindow.GetKeyState(VirtualKey.Menu) & downState) == downState;
                bool controlKey = (coreWindow.GetKeyState(VirtualKey.Control) & downState) == downState;
                bool shiftKey = (coreWindow.GetKeyState(VirtualKey.Shift) & downState) == downState;
                bool noModifiers = !menuKey && !controlKey && !shiftKey;
                bool onlyAlt = menuKey && !controlKey && !shiftKey;

                if (((int)virtualKey == 166 && noModifiers) ||
                    (virtualKey == VirtualKey.Left && onlyAlt))
                {
                    // When the previous key or Alt+Left are pressed navigate back
                    args.Handled = true;
                    this.GoBack(this, new RoutedEventArgs());
                }
                else if (((int)virtualKey == 167 && noModifiers) ||
                    (virtualKey == VirtualKey.Right && onlyAlt))
                {
                    // When the next key or Alt+Right are pressed navigate forward
                    args.Handled = true;
                    this.GoForward(this, new RoutedEventArgs());
                }
            }
        }

        /// <summary>
        /// Invoked on every mouse click, touch screen tap, or equivalent interaction when this
        /// page is active and occupies the entire window.  Used to detect browser-style next and
        /// previous mouse button clicks to navigate between pages.
        /// </summary>
        /// <param name="sender">Instance that triggered the event.</param>
        /// <param name="args">Event data describing the conditions that led to the event.</param>
        private void CoreWindow_PointerPressed(CoreWindow sender,
            PointerEventArgs args)
        {
            var properties = args.CurrentPoint.Properties;

            // Ignore button chords with the left, right, and middle buttons
            if (properties.IsLeftButtonPressed || properties.IsRightButtonPressed ||
                properties.IsMiddleButtonPressed) return;

            // If back or foward are pressed (but not both) navigate appropriately
            bool backPressed = properties.IsXButton1Pressed;
            bool forwardPressed = properties.IsXButton2Pressed;
            if (backPressed ^ forwardPressed)
            {
                args.Handled = true;
                if (backPressed) this.GoBack(this, new RoutedEventArgs());
                if (forwardPressed) this.GoForward(this, new RoutedEventArgs());
            }
        }

        #endregion

        #region Visual state switching

        /// <summary>
        /// Invoked as an event handler, typically on the <see cref="FrameworkElement.Loaded"/>
        /// event of a <see cref="Control"/> within the page, to indicate that the sender should
        /// start receiving visual state management changes that correspond to application view
        /// state changes.
        /// </summary>
        /// <param name="sender">Instance of <see cref="Control"/> that supports visual state
        /// management corresponding to view states.</param>
        /// <param name="e">Event data that describes how the request was made.</param>
        /// <remarks>The current view state will immediately be used to set the corresponding
        /// visual state when layout updates are requested.  A corresponding
        /// <see cref="FrameworkElement.Unloaded"/> event handler connected to
        /// <see cref="StopLayoutUpdates"/> is strongly encouraged.  Instances of
        /// <see cref="LayoutAwarePage"/> automatically invoke these handlers in their Loaded and
        /// Unloaded events.</remarks>
        /// <seealso cref="DetermineVisualState"/>
        /// <seealso cref="InvalidateVisualState"/>
        public void StartLayoutUpdates(object sender, RoutedEventArgs e)
        {
            var control = sender as Control;
            if (control == null) return;
            if (this._layoutAwareControls == null)
            {
                // Start listening to view state changes when there are controls interested in updates
                Window.Current.SizeChanged += this.WindowSizeChanged;
                this._layoutAwareControls = new List<Control>();
            }
            this._layoutAwareControls.Add(control);

            // Set the initial visual state of the control
            VisualStateManager.GoToState(control, DetermineVisualState(ApplicationView.Value), false);
        }

        private void WindowSizeChanged(object sender, WindowSizeChangedEventArgs e)
        {
            this.InvalidateVisualState();
        }

        /// <summary>
        /// Invoked as an event handler, typically on the <see cref="FrameworkElement.Unloaded"/>
        /// event of a <see cref="Control"/>, to indicate that the sender should start receiving
        /// visual state management changes that correspond to application view state changes.
        /// </summary>
        /// <param name="sender">Instance of <see cref="Control"/> that supports visual state
        /// management corresponding to view states.</param>
        /// <param name="e">Event data that describes how the request was made.</param>
        /// <remarks>The current view state will immediately be used to set the corresponding
        /// visual state when layout updates are requested.</remarks>
        /// <seealso cref="StartLayoutUpdates"/>
        public void StopLayoutUpdates(object sender, RoutedEventArgs e)
        {
            var control = sender as Control;
            if (control == null || this._layoutAwareControls == null) return;
            this._layoutAwareControls.Remove(control);
            if (this._layoutAwareControls.Count == 0)
            {
                // Stop listening to view state changes when no controls are interested in updates
                this._layoutAwareControls = null;
                Window.Current.SizeChanged -= this.WindowSizeChanged;
            }
        }

        /// <summary>
        /// Translates <see cref="ApplicationViewState"/> values into strings for visual state
        /// management within the page.  The default implementation uses the names of enum values.
        /// Subclasses may override this method to control the mapping scheme used.
        /// </summary>
        /// <param name="viewState">View state for which a visual state is desired.</param>
        /// <returns>Visual state name used to drive the
        /// <see cref="VisualStateManager"/></returns>
        /// <seealso cref="InvalidateVisualState"/>
        protected virtual string DetermineVisualState(ApplicationViewState viewState)
        {
            return viewState.ToString();
        }

        /// <summary>
        /// Updates all controls that are listening for visual state changes with the correct
        /// visual state.
        /// </summary>
        /// <remarks>
        /// Typically used in conjunction with overriding <see cref="DetermineVisualState"/> to
        /// signal that a different value may be returned even though the view state has not
        /// changed.
        /// </remarks>
        public void InvalidateVisualState()
        {
            if (this._layoutAwareControls != null)
            {
                string visualState = DetermineVisualState(ApplicationView.Value);
                foreach (var layoutAwareControl in this._layoutAwareControls)
                {
                    VisualStateManager.GoToState(layoutAwareControl, visualState, false);
                }
            }
        }

        #endregion

        #region Process lifetime management

        private String _pageKey;

        /// <summary>
        /// Invoked when this page is about to be displayed in a Frame.
        /// </summary>
        /// <param name="e">Event data that describes how this page was reached.  The Parameter
        /// property provides the group to be displayed.</param>
        protected override void OnNavigatedTo(NavigationEventArgs e)
        {
            // Returning to a cached page through navigation shouldn't trigger state loading
            if (this._pageKey != null) return;

            var frameState = SuspensionManager.SessionStateForFrame(this.Frame);
            this._pageKey = "Page-" + this.Frame.BackStackDepth;

            if (e.NavigationMode == NavigationMode.New)
            {
                // Clear existing state for forward navigation when adding a new page to the
                // navigation stack
                var nextPageKey = this._pageKey;
                int nextPageIndex = this.Frame.BackStackDepth;
                while (frameState.Remove(nextPageKey))
                {
                    nextPageIndex++;
                    nextPageKey = "Page-" + nextPageIndex;
                }

                // Pass the navigation parameter to the new page
                this.LoadState(e.Parameter, null);
            }
            else
            {
                // Pass the navigation parameter and preserved page state to the page, using
                // the same strategy for loading suspended state and recreating pages discarded
                // from cache
                this.LoadState(e.Parameter, (Dictionary<String, Object>)frameState[this._pageKey]);
            }
        }

        /// <summary>
        /// Invoked when this page will no longer be displayed in a Frame.
        /// </summary>
        /// <param name="e">Event data that describes how this page was reached.  The Parameter
        /// property provides the group to be displayed.</param>
        protected override void OnNavigatedFrom(NavigationEventArgs e)
        {
            var frameState = SuspensionManager.SessionStateForFrame(this.Frame);
            var pageState = new Dictionary<String, Object>();
            this.SaveState(pageState);
            frameState[_pageKey] = pageState;
        }

        /// <summary>
        /// Populates the page with content passed during navigation.  Any saved state is also
        /// provided when recreating a page from a prior session.
        /// </summary>
        /// <param name="navigationParameter">The parameter value passed to
        /// <see cref="Frame.Navigate(Type, Object)"/> when this page was initially requested.
        /// </param>
        /// <param name="pageState">A dictionary of state preserved by this page during an earlier
        /// session.  This will be null the first time a page is visited.</param>
        protected virtual void LoadState(Object navigationParameter, Dictionary<String, Object> pageState)
        {
        }

        /// <summary>
        /// Preserves state associated with this page in case the application is suspended or the
        /// page is discarded from the navigation cache.  Values must conform to the serialization
        /// requirements of <see cref="SuspensionManager.SessionState"/>.
        /// </summary>
        /// <param name="pageState">An empty dictionary to be populated with serializable state.</param>
        protected virtual void SaveState(Dictionary<String, Object> pageState)
        {
        }

        #endregion

        /// <summary>
        /// Implementation of IObservableMap that supports reentrancy for use as a default view
        /// model.
        /// </summary>
        private class ObservableDictionary<K, V> : IObservableMap<K, V>
        {
            private class ObservableDictionaryChangedEventArgs : IMapChangedEventArgs<K>
            {
                public ObservableDictionaryChangedEventArgs(CollectionChange change, K key)
                {
                    this.CollectionChange = change;
                    this.Key = key;
                }

                public CollectionChange CollectionChange { get; private set; }
                public K Key { get; private set; }
            }

            private Dictionary<K, V> _dictionary = new Dictionary<K, V>();
            public event MapChangedEventHandler<K, V> MapChanged;

            private void InvokeMapChanged(CollectionChange change, K key)
            {
                var eventHandler = MapChanged;
                if (eventHandler != null)
                {
                    eventHandler(this, new ObservableDictionaryChangedEventArgs(change, key));
                }
            }

            public void Add(K key, V value)
            {
                this._dictionary.Add(key, value);
                this.InvokeMapChanged(CollectionChange.ItemInserted, key);
            }

            public void Add(KeyValuePair<K, V> item)
            {
                this.Add(item.Key, item.Value);
            }

            public bool Remove(K key)
            {
                if (this._dictionary.Remove(key))
                {
                    this.InvokeMapChanged(CollectionChange.ItemRemoved, key);
                    return true;
                }
                return false;
            }

            public bool Remove(KeyValuePair<K, V> item)
            {
                V currentValue;
                if (this._dictionary.TryGetValue(item.Key, out currentValue) &&
                    Object.Equals(item.Value, currentValue) && this._dictionary.Remove(item.Key))
                {
                    this.InvokeMapChanged(CollectionChange.ItemRemoved, item.Key);
                    return true;
                }
                return false;
            }

            public V this[K key]
            {
                get
                {
                    return this._dictionary[key];
                }
                set
                {
                    this._dictionary[key] = value;
                    this.InvokeMapChanged(CollectionChange.ItemChanged, key);
                }
            }

            public void Clear()
            {
                var priorKeys = this._dictionary.Keys.ToArray();
                this._dictionary.Clear();
                foreach (var key in priorKeys)
                {
                    this.InvokeMapChanged(CollectionChange.ItemRemoved, key);
                }
            }

            public ICollection<K> Keys
            {
                get { return this._dictionary.Keys; }
            }

            public bool ContainsKey(K key)
            {
                return this._dictionary.ContainsKey(key);
            }

            public bool TryGetValue(K key, out V value)
            {
                return this._dictionary.TryGetValue(key, out value);
            }

            public ICollection<V> Values
            {
                get { return this._dictionary.Values; }
            }

            public bool Contains(KeyValuePair<K, V> item)
            {
                return this._dictionary.Contains(item);
            }

            public int Count
            {
                get { return this._dictionary.Count; }
            }

            public bool IsReadOnly
            {
                get { return false; }
            }

            public IEnumerator<KeyValuePair<K, V>> GetEnumerator()
            {
                return this._dictionary.GetEnumerator();
            }

            System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
            {
                return this._dictionary.GetEnumerator();
            }

            public void CopyTo(KeyValuePair<K, V>[] array, int arrayIndex)
            {
                int arraySize = array.Length;
                foreach (var pair in this._dictionary)
                {
                    if (arrayIndex >= arraySize) break;
                    array[arrayIndex++] = pair;
                }
            }
        }
    }
}

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About the Author

Colin Eberhardt
Architect Scott Logic
United Kingdom United Kingdom
I am CTO at ShinobiControls, a team of iOS developers who are carefully crafting iOS charts, grids and controls for making your applications awesome.
 
I am a Technical Architect for Visiblox which have developed the world's fastest WPF / Silverlight and WP7 charts.
 
I am also a Technical Evangelist at Scott Logic, a provider of bespoke financial software and consultancy for the retail and investment banking, stockbroking, asset management and hedge fund communities.
 
Visit my blog - Colin Eberhardt's Adventures in .NET.
 
Follow me on Twitter - @ColinEberhardt
 
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