SHAZAML! » Tutorials

Hidden Object: Episode 14 – Shake it up

Mark Tucker — Wed, 25 Nov 2009 13:05:17 +0000

So far in the game, we have particles when an item is clicked, a hint to show the location of an unfound item, but what should we do if the player goes berserk and wildly clicks all over the place in hopes of finding a difficult-to-find item? In this episode of Creating a Hidden Object Game is Silverlight 3 we will add an earthquake effect if the player clicks too many times in a 5 second interval.

Let’s first start with the shake effect. The magnifierCanvas Canvas contains the background image and all Paths for each clickable item. We will create a new storyboard called ShakeStoryboard that will animate the Left property of the Canvas:

Each of the 4 key frames set the Left property to a different value as shown in the storyboard XAML:

The Storyboard has the RepeatBehavior property set to repeat 5 times and the SpeedRatio property set to speed up the animation.

If the player clicks on the background image 10 times within a 5 second interval, then the ShakeStoryboard will play. To accomplish this we need three SetGlobalCounterAction instances and one ControlStoryboardAction added to the UserControl:

The first SetGlobalCounterAction sets the values for the TooManyClicks counter when the UserControl loads:

The ControlStoryboardAction plays the ShakeStoryboard when the GlobalCounterMaxReachedTrigger is fired for the TooManyClicks key which we set previously to 10.

When the counter reaches 10 we need to set it back to zero which is what the second SetGlobalCounterAction does:

The final SetGlobalCounterAction uses the TimerTrigger to reset the counter every 5 seconds:

The only thing left to do is add the IncrementGlobalCounterAction to the background image to increment the counter by 1:

So with 5 Action instances, 3 Trigger types, 1 Storyboard, and 0 lines of code we were able to quickly add this feature to the game.

Source Code

Demo

Hidden Object: Episode 13 – Give me a Hint

Mark Tucker — Tue, 17 Nov 2009 19:12:44 +0000

This is episode 13 of Creating a Hidden Object Game is Silverlight 3. In this episode, we will add a hint feature to the game to help the players when they can’t find an item. This will require various animations and a custom behavior.

The hint feature can be segmented into three parts:

Recharging hint button
Hint overlay image with animation
HintBehavior to randomly position the hint overlay image

Hint Button

To make the hint button, we will use an image of a laptop, a TextBlock (hintTextBlock), and a ProgressBar (progressBar) wrapped in a Canvas (hintCanvas):

The idea is that the TextBlock will contain the text “HINT” and act as a button to trigger the hint feature. When the TextBlock is clicked, the TextBlock is hidden and the ProgressBar shown. This is accomplished by adding a HintStates group to the main UserControl:

When the HintState is active, the TextBlock is shown and its IsHitTestVisible property is set to true so that it can be clicked. When the RechargeState is active, the TextBlock’s Opacity property is set to 0 and its IsHitTestVisible property is set to false so that it can’t be clicked.

To set the RechargeState, we add a GoToStateAction to the TextBlock:

A storyboard is added to change the value of the ProgressBar to indicate that the hint is recharging.

In this example, the storyboard will recharge in 10 seconds. For the game, the recharge duration should be somewhere between 30 seconds and 2 minutes.

This storyboard is started using a ControlStoryboardAction on the TextBlock:

The change from RechargeState to HintState is handled by the GoToStateAction and the StoryboardCompletedTrigger waiting on RechargingStoryboard. So as soon as the recharging animation ends, then the Hint button displays again.

Hint Overlay

The hint overlay was created in Expression Design and consists of 10 starbursts or flares set in a circular pattern. After the image is added to the project, drag it onto the LayoutRoot Canvas and locate it “off screen” (Left = 500, Top = -300). Set the ZIndex of the image to 99 so that it will be over any item on the game screen, but always under the cursor image.

When the hint TextBlock is clicked, two storyboards are started. The ShowHintStoryboard changes the opacity from 0% to 80% in 2 seconds and then auto reverses back to 0% over the next 2 seconds. The RotateHintStoryboard uses a RotateTransform to rotate the overlay 360 degrees over 4 seconds.

To start the storyboards, use the ControlStoryboardAction with the EventTrigger:

Hint Behavior

The last thing we need to do is figure out where to put the hint overlay image. To do this, we will use a behavior that exposes a ShowHint command as well as a HintItems collection and a HintOverlayName property:

In the same way that the MouseCursorBehavior exposes the CursorName property to allow selection of the cursor, the HintBehavior exposes the HintOverlayName so that we can select the hint overlay image. An EventTrigger causes the ShowHint command to fire when the HINT TextBlock is clicked.

The HintItems collection contains one HintItem object for each item that can have a hint. The HintItem object contains a TargetName property to identify the Path or object representing the item and an X and Y variance for the location of the overlay.

The HintBehavior uses two NameResolver instances (see episode 12). The first NameResolver changes the HintOverlayName into a reference to the overlay image control. The second NameResolver is used once a HintItem is randomly picked to see if the object still exists and if so gets a reference to it. Even though a HintItem exists for all clickable items in the hidden object game, it may no longer exist in the visual tree as it could have been removed by the RemoveElementAction as discussed in episode 4.

When the ShowHint command is executed, the private OnShowHint method is called. This is the heart of the HintBehavior:

private void OnShowHint()
{
  DependencyObject item = null;
 
  if (!this.IsHintOverlayNameSet)
    return;
 
  FrameworkElement hintOverlay = HintOverlay as FrameworkElement;
 
  //mix up the order of item names
  HintItems.Randomize();
 
  for (int index = 0; index < HintItems.Count; index++)
  {
    this.ItemResolver.Name = HintItems[index].TargetName;
    item = this.ItemResolver.Object;
 
    if (item != null)
    {
      double itemX = (double)item.GetValue(Canvas.LeftProperty);
      double itemWidth = (double)item.GetValue(FrameworkElement.ActualWidthProperty);
      double itemY = (double)item.GetValue(Canvas.TopProperty);
      double itemHeight = (double)item.GetValue(FrameworkElement.ActualHeightProperty);
    
      double newX = RandomWithVariance(itemX + (itemWidth / 2) - (hintOverlay.ActualWidth / 2), HintItems[index].OriginXVariance);
      double newY = RandomWithVariance(itemY + (itemHeight / 2) - (hintOverlay.ActualHeight / 2), HintItems[index].OriginYVariance);
 
      hintOverlay.SetValue(Canvas.LeftProperty, newX);
      hintOverlay.SetValue(Canvas.TopProperty, newY);

      break;
    }
  }
}

If the HintOverlayName is not set we exit the method, otherwise we get a reference to it. We then randomize the order of the items in the HintItems list. This is done using an extension method called Randomize(). Since some items named in the list may no longer exist on the Canvas, we do a null check after we access an item in the list and resolve it. If the item exists, then we determine the location of the item with its width and height so that we can center the overlay image over the item. The RandomWithVariance method uses the OriginXVariance and OriginYVariance values set on HintItem to make sure that the overlay image is over the item but that the item is not necessarily exactly centered.

The hint feature of our hidden object game is fairly simple once we break it into its three main components and work on them individually. Stay tuned for the next episode of Creating a Hidden Object Game in Silverlight 3.

Source Code

Demo

Video: Creating a Silverlight 3 Casual Game using Blend 3 and Triggers, Actions, and Behaviors

Mark Tucker — Mon, 09 Nov 2009 15:19:11 +0000

On Saturday, November 7, 2009 at 9:00am I presented at the Desert Code Camp in Phoenix, AZ. The topic of my presentation was Silverlight casual game development. In less than an hour I demonstrated how to use triggers, actions, and behaviors in Blend 3 to create a hidden object game. Because all code was contained in the TABs (Triggers, Actions, and Behaviors) there was no code behind for the main UserControl.

Here is a link to the presentation video in WMV format.

If you like you can see all the episodes and follow along with the tutorial.

Hidden Object: Episode 12 – Custom Mouse Cursor Behavior

Mark Tucker — Tue, 27 Oct 2009 14:07:09 +0000

This is episode 12 of Creating a Hidden Object Game is Silverlight 3. In this episode, we will create a behavior that allows us to set the shape of the mouse cursor to any Image or Path we desire.

Let start this tutorial in Expression Design. Create a new document that is 25×25 pixels and on the single layer add the shapes shown:

Export the document as a PNG making sure that both Transparency and Antialias are checked.

If you don’t have a copy of Expression Design, you can use a vector graphics program like Inkscape.

Add the image to the Visual Studio project and drag it onto the Canvas. Let’s position the cursor image off screen at: Top = -50 and Left = -5. The -5 positions the cursor so the tip of the arrow is right in the corner and the -50 just to get it off screen. Since this image needs to be over all other objects including the screen Canvas objects, let’s set the ZIndex property to 1000.

We will compensate for the Top value with the OffsetY value in the MouseCursorBehavior that we will create:

The two offset values are dependency properties of type Double whereas CursorName is a string. You will notice that the cursor name has the artboard element picker (target symbol) that allows you to pick an object from the artboard.

Under the Interactivity folder, create a folder called MouseCursor and add three class files: MouseCursorBehavior, NameResolvedEventArgs, and NameResolver.

To get NameResolver and NameResolvedEventArgs, I admit that I used .NET Reflector to understand how the TargetedTriggerAction class was able to get a reference to an instance of the Target class using the string dependency property, TargetName.

Here is a sample usage of the NameResolver class as it relates to the MouseCursorBehavior:

NameResolver cursorResolver = new NameResolver();
cursorResolver.NameScopeReferenceElement = AssociatedObject;
cursorResolver.Name = "cursorArrow";
DependencyObject cursor = cursorResolver.Object;

After creating an instance of the NameResolver, we must assign an object as the NameScopeReferenceElement and set the name of the element that will be our cursor. Calling the Object property on the resolver will return a reference to the object specified by the Name property. The key method in NameResolver is UpdateObjectFromName:

private void UpdateObjectFromName(DependencyObject oldObject)
{
    DependencyObject resolvedObject = null;
    this.ResolvedObject = null;
 
    if (this.NameScopeReferenceElement != null)
    {
        if (!IsElementLoaded(this.NameScopeReferenceElement))
        {
            this.NameScopeReferenceElement.Loaded += new RoutedEventHandler(this.OnNameScopeReferenceLoaded);
            this.PendingReferenceElementLoad = true;
            return;
        }
        if (!string.IsNullOrEmpty(this.Name))
        {
            FrameworkElement actualNameScopeReferenceElement = this.ActualNameScopeReferenceElement;
            if (actualNameScopeReferenceElement != null)
            {
                resolvedObject = actualNameScopeReferenceElement.FindName(this.Name) as DependencyObject;
            }
        }
    }
    this.HasAttempedResolve = true;
    this.ResolvedObject = resolvedObject;
    if (oldObject != this.Object)
    {
        this.OnObjectChanged(oldObject, this.Object);
    }
}

Line 19 shows how NameScopeReferenceElement and Name are used to resolve the actual object.

The MouseCursorBehavior class defines three dependency properties with their corresponding .NET properties:

public static readonly DependencyProperty CursorNameProperty =
     DependencyProperty.Register("CursorName", typeof(string), typeof(MouseCursorBehavior),
     new PropertyMetadata(new PropertyChangedCallback(OnCursorNameChanged)));
 
public static readonly DependencyProperty OffsetXProperty =
    DependencyProperty.Register("OffsetX", typeof(double), typeof(MouseCursorBehavior), null);
    
public static readonly DependencyProperty OffsetYProperty =
    DependencyProperty.Register("OffsetY", typeof(double), typeof(MouseCursorBehavior), null);

In the constructor of the behavior, a NameResolver called cursorResolver is created. In the OnAttached method, the resolver’s NameScopeReferenceElement is set to the AssociatedObject. And in the OnCursorChanged method, the Name property is set to the name of the object to be used as the cursor:

private static void OnCursorNameChanged(DependencyObject obj, DependencyPropertyChangedEventArgs args)
{
    MouseCursorBehavior behavior = (MouseCursorBehavior)obj;
    behavior.CursorResolver.Name = (string)args.NewValue;
}

To get the artboard element picker to show in the Properties panel for the CursorName, add the CustomPropertyValueEditor attribute to the CursorName property and specify the editor for an Element:

[CustomPropertyValueEditor(CustomPropertyValueEditor.Element)]
public string CursorName
{
    get
    {
        return (string)base.GetValue(CursorNameProperty);
    }
    set
    {
        base.SetValue(CursorNameProperty, value);
    }
}

The Cursor property is where the CursorName value is resolved by the NameResolver and the object reference is returned.

Now the behavior has a reference to the image that is being used as a cursor, now it needs to use that instead of the default cursor. In the OnAttached method, the behavior registers to handle the MouseEnter and MouseLeave events of the AssociatedObject. In our case, the MouseCursorBehavior will be attached to the MainPage UserControl which becomes the AssociatedObject. So whenever the mouse enters the area of the UserControl, it will be changed to the arrow:

private void AssociatedObject_MouseEnter(object sender, MouseEventArgs e)
{
    if (!this.IsCursorNameSet)
        return;
 
    FrameworkElement cursor = Cursor as FrameworkElement;
 
    cursor.Visibility = Visibility.Visible;
    AssociatedObject.Cursor = Cursors.None;
    cursor.IsHitTestVisible = false;
 
    this.AssociatedObject.MouseMove += new MouseEventHandler(AssociatedObject_MouseMove);
}

The cursor variable has a reference to the resolved object which is the Image named cursorArrow. We make the image visible and hide the real cursor. We must make the image “invisible” to mouse events so we set the IsHitTestVisible property to false. Finally, we register for the MouseMove event which is responsible for positioning the image wherever the mouse should be:

private void AssociatedObject_MouseMove(object sender, MouseEventArgs e)
{
    if (!this.IsCursorNameSet)
        return;
 
    FrameworkElement cursor = Cursor as FrameworkElement;
 
    Point mousePosition = e.GetPosition(null);
    cursor.Margin = new Thickness(mousePosition.X + OffsetX, mousePosition.Y + OffsetY, 0, 0);
 
}

To position the image, we use the trick of specifying the top and left values of its Margin based on the current mouse postion and the OffsetX and OffsetY dependency properties we defined.

In the MouseLeave event handler, we simply undo what we set in the MouseEnter handler.

I’ve seen a similar approach to custom cursors various places on the Internet. One requirement that I had was the need to specify a cursor at the UserControl level as shown, but then to have a child (or grandchild, etc.) object of that UserControl also have a unique cursor. If you move the mouse over a hidden rectangle on the left side of the screen the cursor will change to a left-facing arrow. Clicking the arrow will take you to another screen which has a hidden rectangle on the right that displays a right-facing arrow to get you pack to the original screen.

In the code, I created two path objects for the arrows just to show that any element could be used for a cursor. If I wanted, I could even have a cursor with multiple objects grouped in a Canvas that use animation storyboards.

When you look at the complete source for this project, you will notice that I use a Stack data structure to keep track of the nested cursors. I am not completely satisfied with the code as it stands, but it works for the present situation. Two things to note. First, the hidden rectangle must have space all around it so that the cursor properly changes from the left arrow to the cursorArrow. Second, I had to do a workaround because the shapes generated from the ParticlesBehavior was interfering with the custom cursor as sometimes a MouseEnter event was being fired with the star shapes but no MouseLevent event.

Check out the code and let me know if you come up with a better solution.

Source Code

Demo

In the next episode, we will add a hint feature that allows the player to see an area of the screen that still has an object to find.

Hidden Object: Episode 11 – Add Custom Shapes to the Particles Behavior

Mark Tucker — Tue, 06 Oct 2009 00:05:27 +0000

This is episode 11 of Creating a Hidden Object Game is Silverlight 3.

Growing up our family didn’t splurge on Lucky Charms cereal, but I remember the TV commercials with Lucky the leprechaun talking about all the fun marshmallow shapes: pink hearts, yellow moons, orange stars, green clovers, and blue diamonds. In later years other shapes appeared such as purple horseshoes, red balloons, rainbows, and pots of gold.

What does this have to do with our hidden object game? Currently the ParticleControl creates only one shape. Circles. Wouldn’t it be great if you could specify the shape of the particles? That’s what I thought and I knew it could easily be done once I saw this discussion post on the CodePlex site for the Silverlight String-To-PathGeometry Converter.

To the existing ParticlesBehavior, we will add two dependency properties with corresponding property get/set blocks:

public static readonly DependencyProperty ParticleShapeProperty =
    DependencyProperty.Register("ParticleShape", typeof(ParticleShape),
    typeof(ParticlesBehavior), null);

public static readonly DependencyProperty CustomShapePathDataProperty =
    DependencyProperty.Register("CustomShapePathData", typeof(string),
    typeof(ParticlesBehavior), null);

The ParticleShape property is an enum with a list of possible shapes and a custom option:

public enum ParticleShape
{
    Circle,
    Square,
    Star4,
    Star5,
    Star8,
    Custom
}

The CustomShapePathData property is a string that holds a special XAML Path markup syntax and is used when the ParticleShape property is set to Custom. Here is an example of a path definition for a triangle:

The value of the Data property is what is set on CustomShapePathData.

The only other change we need to make to ParticlesBehavior is in the OnShowParticles method where we set the ParticleShape and CustomShapePathData on the instance of ParticleControl.

In ParticleControl, we add the same two dependency properties for ParticleShape and CustomShapePathData with their corresponding property get and set.

The Ellipse, Rectangle, and Path all inherit from the Shape base class. So we change all the methods in ParticleControl that worked on an Ellipse to a Shape. In the SpawnParticle method, we call the newly created CreateShape method:

private Shape CreateShape()
{
    string pathData = "";

    switch (ParticleShape)
    {
        case ParticleShape.Circle:
            return new Ellipse();
 
        case ParticleShape.Square:
            return new Rectangle();

        case ParticleShape.Star4:
            pathData = star4;
            break;

        case ParticleShape.Star5:
            pathData = star5;
            break;

        case ParticleShape.Star8:
            pathData = star8;
            break;

        case ParticleShape.Custom:
            if (string.IsNullOrEmpty(CustomShapePathData))
                return new Ellipse();
            else
                pathData = CustomShapePathData;
            break;

        default:
            return new Ellipse();
    }

    string xamlPath = string.Format("", pathData);

    Path path = (Path)System.Windows.Markup.XamlReader.Load(xamlPath);

    return path;
}

If the ParticleShape property is set to Circle or Square, then a new Ellipse or Rectangle is created and returned. If the selected shape is a 4, 5, or 8-pointed star then a string constant containing the Path data syntax is set and a new Path is created using the XamlReader.Load method. If it is a custom shape, then the data is set based on the value of the CustomShapePathData property. If there is no custom path data, then an Ellipse is created.

When we compile the project and open Blend, we will now see the additional properties:

Here is what the custom triangle particles look like as well as the built-in shapes:

One of the best ways to create these custom shapes is in Expression Design. Create a new document that is 100×100 pixels. Use the Pen, Polygon, or Polyline tools to create a path to your desired shape. Or create multiple paths and use Path operations (Unite, Front Minus Back, etc.) to create a single path.

Select the Path and on the Edit menu select Copy XAML. Paste the XAML into Notepad and copy the Data property string and paste it as the CustomShapePathData value:

It’s that easy:

Source code
Demo

In the next episode, we will create a custom mouse cursor and manage its use with a behavior.

Hidden Object: Episode 10 – Counting Items Found with Counter Triggers, Actions & a Behavior

Mark Tucker — Sun, 04 Oct 2009 07:10:46 +0000

In episode 9 of Creating a Hidden Object Game is Silverlight 3 we added additional screens to the game. In this episode, we will add the Win screen and a collection of triggers, actions, & behaviors that work with a global counter.

The Win screen is shown after all 13 items have been clicked. What we need is an integer counter that subtracts one for each item clicked and when the count gets to zero change the state of the MainPage UserControl to show the screen.

Similar to what we did in the last episode, create a new Canvas called winCanvas and position it to the left of the UserControl on the artboard.

In the States panel, add the WinScreen state to the ScreenStates group:

With recording mode on for the WinScreen state, set the Top and Left properties of winCanvas to 0.

All we need to do is figure out a way to trigger a state change to show this screen.

The solution is a variation of the Global State Behavior sample by Christian Schormann which uses a Singleton object containing a Dictionary to hold values based on a key (or tag).

Let’s go step-by-step through the use of the GlobalCounter classes before we look at any code.

The counter store (GlobalCounterStore) has an empty dictionary keyed using a CounterKey. Some trigger invokes SetGlobalCounterAction which sets the initial values for Value, MinValue, and MaxValue in a dictionary item with a CounterKey of “HiddenItems”. In this case the trigger that sets the values is an EventTrigger on the MainPage UserControl for the Loaded event:

Any time that an entry is changed in the counter store, the Changed event is raised which passes Key, Value, MinValue, and MaxValue. Both the ShowGlobalCounterBehavior and the GlobalCounterChangedTrigger handle this event. Since every instance of the GlobalCounterChangedTrigger & ShowGlobalCounterBehavior handle the Changed event they need to have a CounterKey property to determine if they should take any action for that event. In the case of ShowGlobalCounterBehavior, the associated TextBlock’s Text property is set to Value. For the GlobalCounterChangedTrigger any actions are invoked. In this episode, the GlobalCounterChangedTrigger is not used but is included for completeness.

Now that the counter store has been initialized with values, we can use the IncrementGlobalCounterAction to increment the value. In this case we are incrementing the value by -1 which updates the value in the counter store causing the Changed event to fire which is handled by the ShowGlobalCounterBehavior which sets the text on the TextBlock.

The IncrementGlobalCounterAction is invoked for each Path object clicked until the counter reaches the MinValue:

The Changed event is fired to update the TextBlock, but the MinValueReached event is also fired. This is handled by the GlobalCounterMinReachedTrigger which compares its CounterKey with the Key passed in the event and if they match then the trigger invokes its actions. For this episode, there is a GoToStateAction associated with the UserControl that responds to the GlobalCounterMinReachedTrigger and sets the current state to WinScreen which shows winCanvas.

In cases where you want an incrementing counter instead of a decrementing one, pass a positive value for the IncrementCounterValueBy property of IncrementGlobalCounterAction and use the GlobalCounterMaxReachedTrigger.

The global counter classes can be used for many things including a lives counter, health, shield strength, or to keep track of a player’s score.

Here are a class diagram of the GlobalCounterStore and related classes:

Besides the implementation of the Singleton pattern, the most interesting code can be found in the SaveToStore and IncrementCounter methods of GlobalCounterStore:

internal sealed class GlobalCounterStore
{
    private Dictionary store;

    internal void SaveToStore(string key, int value, int minValue, int maxValue)
    {
        if (key == null)
            return;
        var item = new GlobalCounterItem() {Value = value, MinValue = minValue, MaxValue = maxValue };

        if (store.ContainsKey(key))
        {
            store[key] = item;
        }
        else
        {
            store.Add(key, item);
        }

        OnChanged(key, item);
    }

    internal void IncrementCounter(string key, int incrementBy)
    {
        if ((key == null) || !store.ContainsKey(key))
            return;

        int newValue = store[key].Value + incrementBy;
        store[key].Value = newValue;

        OnChanged(key, store[key]);

        if (newValue >= store[key].MaxValue)
            OnMaxValueReached(key, store[key]);

        if (newValue <= store[key].MinValue)
            OnMinValueReached(key, store[key]);
    }
}

The SetGlobalCounterAction is a TriggerAction that defines four dependency properties for CounterKey, CounterValue, CounterMinValue, and CounterMaxValue. The Invoke method calls the SaveToStore method on GlobalCounterStore.

The IncrementGlobalCounterAction is a TargetedTriggerAction that defines dependency properties for CounterKey and IncrementCounterValueBy. It’s Invoke method calls the IncrementCounter method on GlobalCounterStore.

The three triggers are very similar in that each defines a CounterKey dependency property and each adds a handler to an event raised by GlobalCounterStore:

In the case of GlobalCounterMinReachedTrigger, the OnAttached method adds a handler for the GlobalCounterStore’s MinValueReached event whereas the handler is removed in the OnDetaching method:

public class GlobalCounterMinReachedTrigger : TriggerBase
{
    protected override void OnAttached()
    {
        base.OnAttached();
        GlobalCounterStore.Instance.MinValueReached += Instance_MinValueReached;
    }

    protected override void OnDetaching()
    {
        base.OnDetaching();
        GlobalCounterStore.Instance.MinValueReached -= Instance_MinValueReached;
    }

    void Instance_MinValueReached(object sender, GlobalCounterEventArgs e)
    {
        if (CounterKey == null)
            return;

        if (CounterKey == e.Key)
            this.InvokeActions(e);
    }
}

When the MinValueReached event is raised due to a change in the GlobalCounterStore to any dictionary entry regardless of its key, the passed key (e.Key) is compared to the CounterKey property. If the values match, then the actions for this trigger are invoked.

ShowGlobalCounterBehavior is a behavior that can be attached to a TextBlock control and functions is a similar way as the triggers:

It defines the CounterKey property and handles the Changed event raised by GlobalCounterKey:

public class ShowGlobalCounterBehavior : Behavior
{
    protected override void OnAttached()
    {
        base.OnAttached();
        GlobalCounterStore.Instance.Changed += Instance_Changed;
    }

    protected override void OnDetaching()
    {
        base.OnDetaching();
        GlobalCounterStore.Instance.Changed -= Instance_Changed;
    }
 
    void Instance_Changed(object sender, GlobalCounterEventArgs e)
    {
        if (CounterKey == e.Key)
        {
            if (e.Value > e.MaxValue)
                AssociatedObject.Text = e.MaxValue.ToString();
            else if (e.Value < e.MinValue)
                AssociatedObject.Text = e.MinValue.ToString();
            else
                AssociatedObject.Text = e.Value.ToString();
        }
    }
}

It is possible to increment the Value in the counter store by more than 1 so I added checks so that the TextBlock will never show values greater than MaxValue or less than MinValue.

Now it is time to use these classes in Blend. Drop an instance of SetGlobalCounterAction on the UserControl, a GoToStateAction on LayoutRoot, and a IncrementGlobalCounterAction on a Path:

The values for SetGlobalCounterAction are set as follows:

The new GoToStateAction uses GlobalCounterMinReachedTrigger and sets the StateName to WinScreen:

Each path will have an IncrementGlobalCounterAction set with these values:

Finally, we add a TextBlock to our Canvas to hold the count of remaining items and add the ShowGlobalCounterBehavior to it:

The only property to set on the behavior is the CounterKey:

Once we add IncrementGlobalCounterAction to each Path, we can run the game and as we find items the counter will decrement by 1. When the value reaches 0, then the winning screen is shown.

Source code

Demo

In the next episode we will update the Particles Behavior to allow particle custom shapes.

Hidden Object: Episode 9 – Add the Splash, Menu & Options Screens

Mark Tucker — Tue, 29 Sep 2009 23:55:09 +0000

This is episode 9 of Creating a Hidden Object Game is Silverlight 3. In the last episode we added background music. Now we will create a screen to set the music volume. While we are at it, we will create the splash and menu screens.

When the game is finished, it will have a screen flow as follows:

Currently we have been working on the Game screen which in the project is a UserControl called MainPage.xaml. We are going to create the menu, options, and splash screens as Canvas objects that are off screen of MainPage and are at the bottom of the Objects tree (or top of the z-order) so they show up over all other controls. I chose to do this since I want the background music to play during all of these screens and the MediaElement on MainPage is the one that is playing it. There are various other ways to approach this.

Let’s open Blend, add 3 Canvas controls, and name them splashCanvas, menuCanvas, and optionsCanvas. Make each Canvas have a black background and position them on the artboard so that they are to the left of MainPage:

On splashCanvas, add 4 TextBlock controls and enter the title information:

On menuCanvas, add the page title in a TextBlock and 2 Buttons:

On optionsCanvas, add a TextBlock for the page title, a TextBlock for the slider title, a Slider control, and a Button:

Since the silder’s Value property will be used in a Binding for the MediaElement’s Volume property, we will name the slider as sliderMusicVolume.

To control the screen flow, we will use the States panel to create a ScreenStates group with the following states: GameScreen, SplashScreen, MenuScreen, OptionsScreen.

On the States tab, click the Add state group button:

Then next to the ScreenStates group, click the Add state button:

As I entered the following states, I didn’t worry about setting any properties for any of the controls and after adding OptionsScreen I just turned off recording.

The GameScreen state represents when the MainPage is visible which is how it currently is shown on the artboard. No change will need to be made for this state. Click on the SplashScreen state in the States tab to turn on recording mode. Then click splashCanvas and change its Top and Left properties both to 0. Turn off recording of the SplashScreen state.

Repeat for the MenuScreen and OptionsScreen states so that when one of these states is active, MainPage will be covered by menuCanvas or optionsCanvas.

Click on the Base state at the top of the States tab to make sure you are completely out of state editing mode.

We now need to add a TextBlock with the Text property set to “MENU” and add it to LayoutRoot in MainPage. Because I added this control after the Canvas controls for the other screens, I need to change its order in the Objects tree so that it doesn’t appear above those screens. We will worry about making the MENU TextBlock into a Button at a later time.

Now it is time to use the GoToStateAction to connect the screen flow. Drop the first GoToStateAction onto LayoutRoot and change the EventName to Loaded and the StateName to SplashScreen:

This will cause the splash screen to show first.

NOTE: While we are still in development, we can set the loaded StateName to GameScreen to reduce testing time.

Drop another GoToStateAction onto splashCanvas and change the StateName to MenuScreen. When the splash screen is clicked, we will advance to the menu screen:

Drop two more GoToStateAction actions onto the Start and Options buttons on menuCanvas. Change the StateNames to GameScreen and OptionsScreen respectively.

Start button:

Options button:

Drop another GoToStateAction onto the Close button in optionsCanvas and change the StateName to MenuScreen:

Finally, drop the last GoToStateAction onto the MENU TextBlock in MainPage and set the StateName to MenuScreen:

We have just put together the majority of our screen flow with 6 instances of GoToStateAction and no code!

The last thing we need to do is to connect the slider value to the volume of the background music. In the Objects tree, select the musicMediaElement and in the Properties pane, click the peg to the right of the Volume property and click Data Binding to open the Create Data Binding window:

Select the ElementProperty tab. In the Scene elements list, open optionsCanvas and select sliderMusicVolume. In the Properties list, select Value. Now when the slider in the options screen is changed, it will set the volume on the MediaElement playing the background music.

The last thing we need to do is set some values on the slider control. Select the control and change the following properties found in the Common Properties group: LargeChange, Maximum, and Value.

In the next episode, we will try to figure out a way to determine when all the objects have been found so we can show a Win screen.

Demo
Source code

Hidden Object: Episode 8 – Loop Game Music with a Behavior

Mark Tucker — Mon, 28 Sep 2009 13:24:58 +0000

In the last episode of Creating a Hidden Object Game is Silverlight 3 we finished off the magnifier feature. Now it is time to add some background music to the game and have it continually play.

First off, we need to find some appropriate music. I did a search for royalty-free & public domain music and came across a site by Derek R. Audette that contained such music. On the site, I found a piece of music called “Combustible Coffee Pot” written & performed by Derek R. Audette – ©MMV(Socan). Derek’s own description of the music is:

“Out of control drum fills, singing string sections and odd, tense, electronic pads make up this bizarre composition. Created to add a mood of intrigue to an independent film produced in 2005.”

Download the mp3 file and add it to the Audio folder.

In order to use the music in our game, we need to add a MediaElement control to LayoutRoot:

To get the continuous loop, we need to handle the MediaEnded event which sets the media position back to 0 and plays it again:

private void musicElement_MediaEnded(object sender, System.Windows.RoutedEventArgs e)
{
    musicElement.Position = new TimeSpan(0);
    musicElement.Play();
}

But as developers, we don’t want to make our designers go into code behind and enter C# code. Since Silverlight doesn’t support continuously lookping media, we are going to package this functionality into a custom behavior.

Create a folder under Interactivity called ContinuousMediaPlayBehavior and create new class based on the Behavior template by the same name. All we are going to do is attach an event handler to the MediaEnded event in the OnAttached method and remove the handler in the OnDetaching method. To get the AssociatedObject property to be strongly typed to a MediaElement and thus allow this behavior to only be attached to the MediaElement type we change the behavior so it is typed to MediaElement. When the MediaEnded event is fired, we set the position of the media back to 0 and replay it:

public class ContinuousPlayMediaBehavior : Behavior
{
    public ContinuousPlayMediaBehavior() {}

    protected override void OnAttached()
    {
        base.OnAttached();
        AssociatedObject.MediaEnded += AssociatedObject_MediaEnded;
    }

    protected override void OnDetaching()
    {
        base.OnDetaching();
        AssociatedObject.MediaEnded -= AssociatedObject_MediaEnded;
    }

    void  AssociatedObject_MediaEnded(object sender, RoutedEventArgs e)
    {
        AssociatedObject.Position = new TimeSpan(0);
        AssociatedObject.Play();
    }
}

This is what the XAML looks like for this:

In the next episode, we will continue to work on the UI by adding various screens including one to control the volume of the background music we just added.

Hidden Object: Episode 7 – Use an Action to Toggle the Magnifier Behavior

Mark Tucker — Sat, 26 Sep 2009 13:03:42 +0000

This is episode 7 of Creating a Hidden Object Game is Silverlight 3.

In the last few posts we have been working on the magnifier feature of the game which we will finish in this episode.

Please review the following posts:

First we will add in the following files into the ClutteredCube project:

Interactivity folder (from Base Classes for Custom Behaviors)
- BaseBehavior.cs
- BaseBehaviorT.cs
Interactivity\SetInteractionPropertyAction folder (from Creating an Action to set Properties on Actions & Behaviors)
- ConverterHelper.cs
- SetInteractionPropertyAction.cs

The first thing we want to do is to change MagnifierOverBehavior so that it inherits from our custom behavior base class thus inheriting the IsEnabled property:

public class MagnifierOverBehavior : BaseBehavior

The only other change we need to make this behavior is not set the Effect property on MouseEnter but instead in MouseMove based on the value of the IsEnabled property:

private void AssociatedObject_MouseEnter( object sender, MouseEventArgs e )
{
  this.AssociatedObject.MouseMove += new MouseEventHandler( AssociatedObject_MouseMove );
  //this.AssociatedObject.Effect = this.magnifier;
}

private void AssociatedObject_MouseMove( object sender, MouseEventArgs e )
{
  if (IsEnabled)
  {
    if (this.AssociatedObject.Effect != this.magnifier)
    {
      this.AssociatedObject.Effect = this.magnifier;
    }
    ...
  }
}

In Blend, open the MainPage and select the MagnifierOverBehavior in the Object tree under magnifierCanvas. Name the behavior magnifierBehavior and set IsEnabled to false:

From the Assets tab drag two instances of SetInteractionPropertyAction onto the CheckBox magnifier control:

On the first one, set the properties as follows:

EventName: Checked
TargetName: magnifierCanvas
ObjectName: magnifierBehavior
PropertyName: IsEnabled
Value: true

Set the second the same as the first, except:

EventName: Unchecked
Value: false

Make sure that the CheckBox control IsChecked property is false to match the InEnabled value of false for magniferBehavior.

Run the game and verify that magnification is only turned on when the CheckBox is checked.

Let’s do one more thing to finish this episode. Notice that magnifier.png has a white background behind the glass part of the magnifying glass. The image should be on top of something white like a notepad. Import the notepad image and drop it at the bottom of LayoutRoot.

Position it how you want it and move the magnifier CheckBox on top of it.

Source Code

Demo

There are many features to add so I will keep the next episode contents a surprise.

Hidden Object: Episode 6 – Create a CheckBox from an Image

Mark Tucker — Sat, 26 Sep 2009 11:39:04 +0000

This is episode 6 of Creating a Hidden Object Game is Silverlight 3.

In our last official episode, we added the MagnifierOverBehavior, but now the magnifier is on all the time. To allow the player to turn it on or off, we will create a CheckBox control from an image of a magnifying glass. Creating controls from objects on the artboard is really powerful.

Start Blend and add the image of the magnifying glass to the Images folder then drag an instance of it onto the bottom of LayoutRoot. With the image still selected, right click and select Make Into Control… from the context menu.

Select the CheckBox control from the list, enter the name as MagnifierCheckBoxStyle and define it in the Application. Click OK to create the control and have it open on the artboard.

Select the image and set its Stretch to Uniform.
Select the ContentPresenter and move it below the image.
Select the Grid and set the Height to 70 and the Width to 100.

Now we are going to change the States associated with this CheckBox. In this case the Checked state will show the ContentPresenter while the UnChecked state will set the Opacity to 0%

Click on the States tab and then on the Unchecked state in the CheckStates group. There will be a red dot next to Unchecked indicating that state recording is on. Click on the ContentPresenter and set the Opacity to 0%:

Click on the Unchecked state to turn recording off.

For the MouseOver state, we will add a glow effect using the DropShadowEffect. Click on the MouseOver state in the CommonStates group to turn on recording. Click the Image and set its Effect property to a DropShadowEffect:

I changed the Direction and ShadowDepth to 0 and the Color to Yellow.

Click on the MouseOver state to turn off recording.

Close the style editor and with the styled CheckBox selected, set the Content value to the text: “x2″. You might also want to set the Text size to about 14 pt and change the Foreground color of the text.

Run the application and verify the Checked, Unchecked, and MouseOver states.

The completed style looks like this:

Now we have a control to use to toggle the magnification state. In the next episode we will use the behavior base classes, SetInteractionPropertyAction, and this styled CheckBox to complete the magnification feature.