Building Silverlight Chord Factory: Part 1 – The Data Model

Back in November 2008 I posted about converting my reference app Chord Factory to Silverlight – Chord Factory is a piano chord finder utility that I wrote years ago and I have been porting from one development platform to the next as a series of protracted learning exercises ever since. It started out as a VB6 WinForms app and has been through various .NET incarnations since. The Silverlight version went through partially complete Silverlight 2.0 and 3.0 versions in a fairly monolithic architecture and I always meant to produce a few posts about the code once I had it complete and had a published version on my website.
But before I had managed that (see the most recent incomplete version here) I became interested in overhauling the component design and re-architecting it as another learning exercise, this time to help me work through the concepts of producing loosely-coupled component designs using MVC/MVVM patterns and looking at concerns like unit testing & testability together with an attempt at expressing the data structures involved in XML.
I long since gave up trying to make the UI pretty – whilst I think I can distinguish good UI/UX from bad I am no designer, but I have managed to produce something that fits some of the MVVM principles and allowed me to understand how MVVM works and makes for testable components and clean data-binding. And before I get distracted again and feel the urge to overhaul the code again and douse everything in MEF, it is time for those long-delayed posts.

Representing note sequences as data

Without straying too much into music theory, chords and musical scales are basically sequences of notes – the 8 notes in a scale (e.g. the scale of C Major: C-D-E-F-G-A-B-C) or the 3, 4 or more notes in a chord (e.g. the chord of C Major: C-E-G) can be stored and positions or offsets in a sequence. However the progressive sequence is measured in pitch-steps of semitones from the starting note i.e. including the black notes (looking at the piano keyboard, the semitone sequence starting from the note C is: C, C#, D, Eb, E, F, F#, G, Ab, A, B, C, C#, D, Eb… and so on up the keyboard). So to store the sequence for the scale of C Major we need to store offsets for the 1st, 3rd, 5th, 6th, 8th, 10th, 11th and 12th semitones, and for the chord of C Major we need to store the offsets for the 1st, 5th and 7th. With this information for a scale or a chord we have the means to select or highlight on the UI representation of our piano keyboard the notes that make it up, starting at the base or root note – C in the previous examples.
We can now store these sequences of offsets for all the standard scales and chords that musicians have come up with and use them to produce representations of any variation from a particular root note. An XML schema for these sequences is simple to produce: 

CHORD DATA SCHEMA

1. <?xml version="1.0" encoding="utf-8"?>
2. <xs:schema targetNamespace="http://tempuri.org/XMLSchema.xsd"
3.            elementFormDefault="qualified"
4.            xmlns="http://tempuri.org/XMLSchema.xsd"
5.            xmlns:mstns="http://tempuri.org/XMLSchema.xsd"
6.            xmlns:xs="http://www.w3.org/2001/XMLSchema">
7.   <xs:element name="ChordFactoryData">
8.     <xs:complexType>
9.       <xs:sequence>
10.         <xs:element name="Chords" type="Chords" />
11.         <xs:element name="Scales" type="Scales" />
12.       </xs:sequence>
13.     </xs:complexType>
14.   </xs:element>
15.   <xs:complexType name="Chords">
16.     <xs:sequence>
17.       <xs:element name="Chord" minOccurs="1" maxOccurs="unbounded" type="NoteSequence" />
18.     </xs:sequence>
19.   </xs:complexType>
20.   <xs:complexType name="Scales">
21.     <xs:sequence>
22.       <xs:element name="Scale" minOccurs="1" maxOccurs="unbounded" type="NoteSequence" />
23.     </xs:sequence>
24.   </xs:complexType>
25.   <xs:complexType name="NoteSequence">
26.     <xs:sequence>
27.       <xs:element name="SequenceType" type="SequenceType" maxOccurs="1" minOccurs="1" />
28.       <xs:element name="Description" type="xs:string" maxOccurs="1" minOccurs="1" />
29.       <xs:element name="NoteList" type="NoteList" maxOccurs="1" minOccurs="1" />
30.     </xs:sequence>
31.   </xs:complexType>
32.   <xs:complexType name="NoteList">
33.     <xs:sequence>
34.       <xs:element name="NoteIndex" type="xs:int" minOccurs="1" maxOccurs="unbounded" />
35.     </xs:sequence>
36.   </xs:complexType>
37.   <xs:simpleType name="SequenceType">
38.     <xs:restriction base="xs:string">
39.       <xs:enumeration value="Chord" />
40.       <xs:enumeration value="Scale" />
41.     </xs:restriction>
42.   </xs:simpleType>
43. </xs:schema>

 

The XML for a Major Chord would then look like this:

MAJOR CHORD

1. <chords>
2.   <chord>
3.     <sequencetype>Chord</sequencetype>
4.     <description>Major</description>
5.     <notelist>
6.       <noteindex>0</noteindex>
7.       <noteindex>4</noteindex>
8.       <noteindex>7</noteindex>
9.     </notelist>
10.   </chord>
11.  
12.   ...more chords...
13.  
14. </chords>

 

and a Major Scale would look like this:

MAJOR SCALE

1. <scales>
2.   <scale>
3.     <sequencetype>Scale</sequencetype>
4.     <description>Major</description>
5.     <notelist>
6.       <noteindex>0</noteindex>
7.       <noteindex>2</noteindex>
8.       <noteindex>4</noteindex>
9.       <noteindex>5</noteindex>
10.       <noteindex>7</noteindex>
11.       <noteindex>9</noteindex>
12.       <noteindex>11</noteindex>
13.       <noteindex>12</noteindex>
14.     </notelist>
15.   </scale>
16.  
17.   ...more scales...
18.  
19. </scales>

 

Data Classes

In my MVVM implementation this Chord and Scale data is loaded into models that represent the Chord or the Scale and I can then produce collections of instances of all the Chords and Scales. Here are the simple models in C#:

DATA MODEL CLASSES

1. public abstract class NoteSequence
2. {
3.     public List<int> Notes { get; set; }
4.     public string Description { get; set; }
5. }
6.  
7. public class Chord : NoteSequence
8. {
9.     public static Chord CreateNewChord()
10.     {
11.         return new Chord();
12.     }
13.  
14.     public static Chord CreateChord(string description, List<int> notes)
15.     {
16.         return new Chord
17.         {
18.             Notes = notes,
19.             Description = description
20.         };
21.     }
22.  
23.     protected Chord() { }
24. }
25.  
26. public class Scale : NoteSequence
27. {
28.     public static Scale CreateNewScale()
29.     {
30.         return new Scale();
31.     }
32.  
33.     public static Scale CreateScale(string description, List<int> notes)
34.     {
35.         return new Scale
36.         {
37.             Notes = notes,
38.             Description = description
39.         };
40.     }
41.  
42.     protected Scale() { }
43. }

In implementation, the Chord and Scale classes are no different and it could be argued that the respective data could be loaded into two collections of the more general NoteSequence class (which would have to be changed from its current abstract incarnation of course); but I prefer to keep them as separate classes as they are logically different and might diverge in the future.

So I now represent my chord and scale data as XML and I have a straightforward model for instantiating it in data objects. The next stage is to load that data into a ViewModel using data access code that will deserialize the XML into the objects. That will be in part 2.

Five Minute Silverlight 4 Aides-Memoire #7 – IDataErrorInfo

The XAML:

DATA INPUT

1. <Grid x:Name="LayoutRoot">
2.   <Grid.Resources>
3.     <local:Person x:Key="NewJoiner" Age="49" Forename="Fred" Surname="Flintstone" />
4.   </Grid.Resources>
5.   <Grid DataContext="{StaticResource NewJoiner}">
6.     <Grid.ColumnDefinitions>
7.       <columndefinition Width="1*" />
8.       <columndefinition Width="5*" />
9.     </Grid.ColumnDefinitions>
10.     <Grid.RowDefinitions>
11.       <rowdefinition Height="50" />
12.       <rowdefinition Height="50" />
13.       <rowdefinition Height="50" />
14.     </Grid.RowDefinitions>
15.     <Grid.Resources>
16.       <Style TargetType="TextBlock">
17.         <setter Property="Margin" Value="10" />
18.         <setter Property="HorizontalAlignment" Value="Right" />
19.         <setter Property="VerticalAlignment" Value="Center" />
20.       </Style>
21.       <Style TargetType="TextBox">
22.         <setter Property="Margin" Value="10" />
23.         <setter Property="Width" Value="154" />
24.         <setter Property="HorizontalAlignment" Value="Left" />
25.         <setter Property="VerticalAlignment" Value="Center" />
26.       </Style>
27.     </Grid.Resources>
28.     <TextBlock Text="First Name" Grid.Row="0" Grid.Column="0" />
29.     <TextBlock Text="Last Name" Grid.Row="1" Grid.Column="0" />
30.     <TextBlock Text="Age" Grid.Row="2" Grid.Column="0" />
31.     <textbox x:Name="Forename" Grid.Row="0" Grid.Column="1" Text="{Binding Forename, Mode=TwoWay, ValidatesOnDataErrors=True}" />
32.     <textbox x:Name="Surname" Grid.Row="1" Grid.Column="1" Text="{Binding Surname, Mode=TwoWay, ValidatesOnDataErrors=True}" />
33.     <textbox x:Name="Age" Grid.Row="2" Grid.Column="1" Text="{Binding Age, Mode=TwoWay, ValidatesOnDataErrors=True}" />
34.   </Grid>
35. </Grid>

The code:

IMPLEMENTATION

1. public class Person : IDataErrorInfo
2. {
3.     public string Forename { get; set; }
4.     public string Surname { get; set; }
5.     public int Age { get; set; }
6.     public string Error { get { return null; } }
7.  
8.     public string this[string columnName]
9.     {
10.         get
11.         {
12.             string error = null;
13.             switch (columnName)
14.             {
15.                 case "Forename":
16.                     if (string.IsNullOrEmpty(Forename))
17.                         error = "Forename required";
18.                     break;
19.                 case "Surname":
20.                     if (string.IsNullOrEmpty(this.Surname))
21.                         error = "Surname required";
22.                     break;
23.                 case "Age":
24.                     if (this.Age < 0 || this.Age > 130)
25.                         error = "Invalid Age";
26.                     break;
27.             }
28.             return error;
29.         }
30.     }
31. }

The result:

Five Minute Silverlight 4 Aides-Memoire #6 – Right Mouse Event Support

<Popup x:Name="PopupMenu" IsOpen="False">
    <ListBox x:Name="MenuItems">
        <ListBoxItem Content="Item 1" />
        <ListBoxItem Content="Item 2" />
        <ListBoxItem Content="Item 3" />
        <ListBoxItem Content="Item 4" />
    </ListBox>
</Popup>

public MainPage()
{
    InitializeComponent();
    MouseRightButtonDown += (s, e) => e.Handled = true;
    MouseRightButtonUp += MainPage_MouseRightButtonUp;
    MenuItems.MouseLeftButtonUp += MenuItems_MouseLeftButtonUp;
}

void MainPage_MouseRightButtonUp(object sender, System.Windows.Input.MouseButtonEventArgs e)
{
    this.PopupMenu.HorizontalOffset = e.GetPosition(this).X;
    this.PopupMenu.VerticalOffset = e.GetPosition(this).Y;
    this.PopupMenu.IsOpen = true;
}

void MenuItems_MouseLeftButtonUp(object sender, System.Windows.Input.MouseButtonEventArgs e)
{
    PopupMenu.IsOpen = false;
    System.Diagnostics.Debug.WriteLine(((sender as ListBox).SelectedItem as ListBoxItem).Content);
}

Five Minute Silverlight 4 Aides-Memoire #5 – Rich Text Area Control

<RichTextArea x:Name="Editor">
    <RichTextArea.Blocks>
        <Paragraph>
            <Run Foreground="Blue" Text="This is "/>
            <Run Foreground="Red" FontWeight="Bold" Text="some sample " />
            <Run FontStyle="Italic" Text="text" />
        </Paragraph>
        <Paragraph>
            <Run Text="Here is "/>
            <Run TextDecorations="Underline" Text="some more" />
        </Paragraph>
    </RichTextArea.Blocks>
</RichTextArea>

void UnderlineSelection_Click(object sender, RoutedEventArgs e)
{
    var currentValue = this.Editor.Selection.GetPropertyValue(TextElement.TextDecorationsProperty);
    TextDecorationCollection setValue = TextDecorations.Underline;
    if (currentValue != DependencyProperty.UnsetValue)
        setValue = (TextDecorationCollection)currentValue == setValue ? null : setValue;
    this.Editor.Selection.SetPropertyValue(TextElement.TextDecorationsProperty, setValue);
}

void ItalicSelection_Click(object sender, RoutedEventArgs e)
{
    var currentValue = this.Editor.Selection.GetPropertyValue(TextElement.FontStyleProperty);
    FontStyle setValue = FontStyles.Italic;
    FontStyle defaultValue = FontStyles.Normal;
    if (currentValue != DependencyProperty.UnsetValue)
        setValue = (FontStyle)currentValue == setValue ? defaultValue : setValue;
    this.Editor.Selection.SetPropertyValue(TextElement.FontStyleProperty, setValue);
}

void BoldSelection_Click(object sender, RoutedEventArgs e)
{
    var currentValue = this.Editor.Selection.GetPropertyValue(TextElement.FontWeightProperty);
    FontWeight setValue = FontWeights.Bold;
    FontWeight defaultValue = FontWeights.Normal;
    if (currentValue != DependencyProperty.UnsetValue)
        setValue = (FontWeight)currentValue == setValue ? defaultValue : setValue;
    this.Editor.Selection.SetPropertyValue(TextElement.FontWeightProperty, setValue);
}

Five Minute Silverlight 4 Aides-Memoire #4 – Clipboard Access

private void PopButton_Click(object sender, RoutedEventArgs e)
{
    var newPara = new Paragraph();

    newPara.Inlines.Add(new Run { Text = Clipboard.GetText() });

    this.rightRichTextArea.Blocks.Add(newPara);
}

private void PushButton_Click(object sender, RoutedEventArgs e)
{
    Clipboard.SetText(this.leftRichTextArea.Selection.Text);
}

Five Minute Silverlight 4 Aides-Memoire #3 – WebCam/Microphone Device Support

<UserControl.Resources>
    <Style x:Key="ListBoxStyle" TargetType="ListBox">
        <Setter Property="ItemTemplate">
            <Setter.Value>
                <DataTemplate>
                    <Image Margin="5" Source="{Binding}" Stretch="UniformToFill" Height="80" VerticalAlignment="Center"/>
                </DataTemplate>
            </Setter.Value>
        </Setter>
        <Setter Property="ItemsPanel">
            <Setter.Value>
                <ItemsPanelTemplate>
                    <StackPanel Orientation="Horizontal" VerticalAlignment="Center" HorizontalAlignment="Center"/>
                </ItemsPanelTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</UserControl.Resources>

<StackPanel Grid.Row="2" Grid.Column="0">
    <Button Content="Start WebCam" Click="StartWebCam_Click" Height="30" />
    <Button Content="Snapshot" Click="Snapshot_Click" Height="30" />
</StackPanel>
<Rectangle Grid.Row="0" Stretch="Fill" Grid.Column="1" x:Name="CapturedImage" />
<ListBox Grid.Row="1" Margin="10" Grid.RowSpan="2" Grid.Column="1" x:Name="Snapshots" Style="{StaticResource ListBoxStyle}"/>

private void StartWebCam_Click(object sender, RoutedEventArgs e)
{
    if (!CaptureDeviceConfiguration.AllowedDeviceAccess & !CaptureDeviceConfiguration.RequestDeviceAccess())
        return;

    VideoBrush videoBrush = new VideoBrush();
    videoBrush.SetSource(captureSource);
    CapturedImage.Fill = videoBrush;
    this.Snapshots.ItemsSource = snaps;
    captureSource.Start();
}

private void Snapshot_Click(object sender, RoutedEventArgs e)
{
    captureSource.AsyncCaptureImage((image) => { snaps.Add(image); });
}

Five Minute Silverlight 4 Aides-Memoire #2 – Printing

private void Print_Click(object sender, RoutedEventArgs e)
{
    PrintDocument printDoc = new PrintDocument();

    // Name that will show in the spooler...
    printDoc.DocumentName = "Directory Tree";
    printDoc.PrintPage += new EventHandler<PrintPageEventArgs>(printDoc_PrintPage);
    printDoc.Print();
}

private void printDoc_PrintPage(object sender, PrintPageEventArgs e)
{
    // Needs a UIElement (visual tree)
    e.PageVisual = DirectoriesTreeView;

    // Setting true will ensure PrintPage is called again for subsequent pages
    e.HasMorePages = false;
}

Five Minute Silverlight 4 Aides-Memoire #1 – Drag and Drop

Build a hierarchical treeview of files and directories dropped from a Windows Explorer window. Requires elevated trust running out of browser to avoid security exceptions when accessing the directory information in the FileInfo objects returned from the e.Data.GetData call.

<Grid x:Name="LayoutRoot" AllowDrop="True" Drop="LayoutRoot_Drop">
    <my:TreeView x:Name="DirectoriesTreeView" Margin="50" Width="500" />
</Grid>

private void LayoutRoot_Drop(object sender, DragEventArgs e)
{
    if (!Application.Current.HasElevatedPermissions  e.Data == null)
        return;

    FileInfo[] fileInfos = e.Data.GetData(DataFormats.FileDrop) as FileInfo[];
    if (fileInfos == null)
        return;
    List<FileInfo> sortedList = new List<FileInfo>(fileInfos);

    sortedList.Sort((x, y) =>
    {
        if (x.Attributes == FileAttributes.Directory && y.Attributes != FileAttributes.Directory)
            return -1;
        if (y.Attributes == FileAttributes.Directory && x.Attributes != FileAttributes.Directory)
            return 1;
        return x.Name.CompareTo(y.Name);
    });

    foreach (FileInfo fileInfo in sortedList)
    {
        var newNode = new TreeViewItem { Header = fileInfo.Name };
        DirectoriesTreeView.Items.Add(newNode);
        if (!fileInfo.Exists)
            ProcessDirectory(fileInfo, newNode);
    }
}

private static void ProcessDirectory(FileSystemInfo fileSystemInfo, TreeViewItem currentNode)
{
    DirectoryInfo directoryInfo = new DirectoryInfo(fileSystemInfo.FullName);

    foreach (FileSystemInfo childFileSystemInfo in directoryInfo.EnumerateFileSystemInfos())
    {
        var newNode = new TreeViewItem { Header = childFileSystemInfo.Name };
        currentNode.Items.Add(newNode);
        if (childFileSystemInfo.Attributes == FileAttributes.Directory)
            ProcessDirectory(childFileSystemInfo, newNode);
    }
}

Silverlight 4

Quite unexpectedly, at least I wasn’t expecting it, today saw the announcement of the first beta of Silverlight 4 at PDC09 in Los Angeles. Barely has version 3 made it out there, but we have a new beta to play with together with another rev of Blend to support it (and .NET 4 in general).
A quick run through the main features in the beta:

• Printing – Full access to the regular print facilities of the host machine – the print dialog and print preview features – so long to all the writable bitmaps and HTML bridge hacks
• Webcam/microphone support – Subject to UAC/user confirmation, you can now programmatically get access to connected devices, capture video, stills and audio input streams
• A Rich TextBox control – the WPF RTF control makes its appearance in Silverlight – embed other UI Elements, control text Runs and other formatting such as Text Decorations
• Clipboard Access – Programmatic access to the clipboard – again subject to UAC
• Right Mouse Context Menus – Full control of a customisable context menu – add whatever you want to it and respond to selection events
• Drag-Drop Drop-Target support Silverlight apps can now act as drag-drop drop-targets receiving file information for the dropped file object(s)
• MVVM Commanding – Finally proper implementation of the ICommand interface – no longer a need to kludge it via bindings to helper classes
• IDataErrorInfo/Validation support – Integration of the support for the IDataErrorInfo interface in Silverlight’s DataBinding giving a validation framework for input controls to leverage in consistently surfacing data input errors with asynchronous data validation
• String Formatting in Binding Extensions – As with WPF, Silverlight has been retrofitted with improved formatting support in the binding extension to give better control over stuff like date, time and other formatting for locales and long and short formatting
• Out of Browser improvements: HTML content - Hosting of HTML content within the Silverlight app; Notifications (aka toast) support; Elevated Trust (again via UAC) access to the My Documents, My Videos, My Pictures special folders; Cross domain access and Full keyboard access in Full Screen mode
• Better tooling and integration of RIA/ADO Services/WCF/MEF

Lots to check out and try out – exciting stuff!

Five Minute Silverlight 3 Aides-Memoire #5 – Based on Styles

    <UserControl.Resources>
        <Style x:Key="ColouredContentControlStyle" TargetType="ContentControl">
            <Setter Property="Height" Value="30" />
            <Setter Property="Width" Value="100" />
            <Setter Property="Margin" Value="10" />
            <Setter Property="FontFamily" Value="Verdana" />
            <Setter Property="FontSize" Value="14" />
            <Setter Property="FontStyle" Value="Italic" />
        </Style>
        
        <Style x:Key="ColouredCheckBoxStyle" BasedOn="{StaticResource ColouredContentControlStyle}" TargetType="CheckBox">
            <Setter Property="Width" Value="154" />
        </Style>
        
        <Style x:Key="RedButtonStyle" BasedOn="{StaticResource ColouredContentControlStyle}" TargetType="Button">
            <Setter Property="Foreground" Value="Red" />
        </Style>
        <Style x:Key="GreenButtonStyle" BasedOn="{StaticResource ColouredContentControlStyle}" TargetType="Button">
            <Setter Property="Foreground" Value="Green" />
        </Style>
        <Style x:Key="YellowCheckBoxStyle" BasedOn="{StaticResource ColouredCheckBoxStyle}" TargetType="CheckBox">
            <Setter Property="Foreground" Value="Yellow" />
        </Style>
        <Style x:Key="OrangeRadioButtonStyle" BasedOn="{StaticResource ColouredContentControlStyle}" TargetType="RadioButton">
            <Setter Property="Foreground" Value="Orange" />
            <Setter Property="Width" Value="190" />
            <Setter Property="FontWeight" Value="Bold" />
        </Style>
    </UserControl.Resources>
    <Grid x:Name="LayoutRoot">
        <Grid.Background>
            <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
                <GradientStop Color="Black" Offset="0"/>
                <GradientStop Color="White" Offset="1"/>
            </LinearGradientBrush>
        </Grid.Background>
        <StackPanel Orientation="Vertical" Margin="20">
            <Button Style="{StaticResource RedButtonStyle}" Content="Red Button" />
            <CheckBox Style="{StaticResource YellowCheckBoxStyle}" Content="Yellow CheckBox" />
            <RadioButton Style="{StaticResource OrangeRadioButtonStyle}" Content="Orange RadioButton" />
            <Button Style="{StaticResource GreenButtonStyle}" Content="Green Button" />
        </StackPanel>
    </Grid>