First cut.

.gitignore

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+app.config
+out/
+
+.vscode/
+*.swp
+*.swo

Makefile

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+SRC :=  $(wildcard src/*.cs)
+OUTPUT := out
+
+all: init compile
+
+init:
+	mkdir -p $(OUTPUT)
+
+compile:
+	csc $(SRC) /nologo /warnaserror \
+		/d:TRACE \
+		/target:winexe /out:$(OUTPUT)/asl-charts.exe
+	cp app.config $(OUTPUT)/asl-charts.exe.config
+
+clean:
+	rm -r $(OUTPUT)

data/config.json

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+{}

src/JsonConfig.cs

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+using System ;
+using System.Text ;
+using System.IO ;
+using System.Runtime.Serialization.Json ;
+using System.Xml ;
+using System.Xml.Linq ;
+using System.Xml.XPath ;
+
+// --------------------------------------------------------------------
+
+public class JsonConfig
+{
+    private XElement mRootElem ;
+
+    public JsonConfig( string caption, string fname )
+    {
+        // load the JSON config
+        string data ;
+        if ( File.Exists( fname ) ) {
+            Program.logTraceMsg( String.Format( "Loading {0}: {1}", caption, Path.GetFullPath(fname) ) ) ;
+            data = File.ReadAllText( fname ) ;
+        } else
+            data ="{}" ;
+        var jsonReader = JsonReaderWriterFactory.CreateJsonReader(
+             Encoding.UTF8.GetBytes( data ),
+             new XmlDictionaryReaderQuotas()
+        ) ;
+        mRootElem = XElement.Load( jsonReader ) ;
+    }
+
+    public string getStringVal( string xpath, string defaultVal="" )
+    {
+        // return the specified value
+        var elem = mRootElem.XPathSelectElement( xpath ) ;
+        if ( elem == null )
+            return defaultVal ;
+        return elem.Value ;
+    }
+
+    public int getIntVal( string xpath, int defaultVal=0 )
+    {
+        // return the specified value
+        try {
+            return Int32.Parse( getStringVal( xpath ) ) ;
+        } catch( System.FormatException ) {
+            return defaultVal ;
+        }
+    }
+}

src/MainForm.cs

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+using System ;
+using System.Text ;
+using System.Drawing ;
+using System.IO ;
+using System.Runtime.InteropServices ;
+using System.Collections.Generic ;
+using System.Windows.Forms ;
+using System.Diagnostics ;
+
+// --------------------------------------------------------------------
+
+public class MainForm : Form
+{
+    private readonly HashSet<string> mValidImageExtensions = new HashSet<string>{ ".png", ".jpg", ".gif" } ;
+
+    private Dictionary<string,Image> mImages = new Dictionary<string,Image>() ;
+    private Dictionary<string,Image>.Enumerator mImagesIter ;
+
+    private PictureBox mImagePictureBox = new PictureBox() ;
+
+    public MainForm()
+    {
+        // initialize the form
+        this.Text = Program.APP_NAME ;
+        this.MinimumSize = new Size( 800, 500 ) ;
+
+        // initialize the form
+        // FIXME! We will probably need something better to render the images, but this will do, for now...
+        this.mImagePictureBox.Dock = DockStyle.Fill ;
+        this.mImagePictureBox.SizeMode = PictureBoxSizeMode.Zoom ;
+        this.Controls.Add( mImagePictureBox ) ;
+
+        // initialize handlers
+        this.Load += new EventHandler( this.MainForm_Load ) ;
+        this.KeyDown += new System.Windows.Forms.KeyEventHandler( this.MainForm_KeyDown ) ;
+    }
+
+    private void MainForm_Load( object sender, EventArgs args )
+    {
+        // locate the image files
+        string dataDir = Path.GetFullPath( Program.dataDir ) ;
+        IEnumerable<string> files = Directory.EnumerateFiles(
+            dataDir, "*.*", SearchOption.AllDirectories
+        ) ;
+        foreach( string fname in files ) {
+            string extn = Path.GetExtension( fname ).ToLower() ;
+            if ( ! mValidImageExtensions.Contains( extn ) )
+                continue ;
+            string fname2 = Path.GetFullPath( fname ) ;
+            if ( fname2.StartsWith( dataDir ) ) {
+                fname2 = fname.Substring( dataDir.Length ) ;
+                if ( fname2.StartsWith( "/" ) || fname2.StartsWith( "\\" ) )
+                    fname2 = fname2.Substring( 1 ) ;
+            } else {
+                // NOTE: I don't think we should ever get here :-/ If we do, the user will have to manage
+                // their configuration using full paths for the image files, but at least we will still run...
+            }
+            Program.logTraceMsg( String.Format( "Loading image: {0}", fname2 ) ) ;
+            mImages[ fname2 ] = Image.FromFile( fname ) ;
+        }
+        mImagesIter = mImages.GetEnumerator() ;
+    }
+
+    private void MainForm_KeyDown( object sender, KeyEventArgs args )
+    {
+        // FIXME! For now, we just allow the user to cycle through the loaded images.
+        if ( args.KeyCode == Keys.Space ) {
+            // show the next image
+            KeyValuePair<String,Image> val ;
+            if ( ! mImagesIter.MoveNext() ) {
+                mImagesIter = mImages.GetEnumerator() ;
+                mImagesIter.MoveNext() ;
+            }
+            val = mImagesIter.Current ;
+            mImagePictureBox.Image = val.Value ;
+        }
+    }
+}

src/Program.cs

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+using System ;
+using System.Windows.Forms ;
+using System.IO ;
+using System.Diagnostics ;
+
+// --------------------------------------------------------------------
+
+public static class Program
+{
+    public const string APP_NAME = "ASL Charts" ;
+
+    private static string mBaseDir ;
+    private static string mDataDir ;
+    private static JsonConfig mAppConfig = null ;
+    private static JsonConfig mDebugConfig = null ;
+    private static MainForm mMainForm = null ;
+
+    [STAThread]
+    static void Main( string[] args )
+    {
+        // initialize
+        mBaseDir = Application.StartupPath ;
+
+        // locate the data directory
+        mDataDir = System.IO.Path.Combine( mBaseDir , "data" ) ;
+        if ( ! Directory.Exists( mDataDir ) ) {
+            mDataDir = System.IO.Path.Combine( mBaseDir , "../data" ) ;
+            if ( ! Directory.Exists( mDataDir ) )
+                mDataDir = mBaseDir ;
+        }
+
+        try {
+
+            // load the app config
+            // NOTE: It would be nice to be able to load the app config from another location, but it seems
+            // we need to create a new AppDomain to do this, and it doesn't work with Mono :-/
+            mAppConfig = new JsonConfig( "app config", Path.Combine( mDataDir, "config.json" ) ) ;
+
+            // load the debug config
+            mDebugConfig = new JsonConfig( "debug config", Path.Combine( mBaseDir, "debug.json" ) ) ;
+
+        } catch( Exception ex ) {
+            showErrorMsg( "Initialization failed:\n\n" + ex.Message ) ;
+            return ;
+        }
+
+        // run the application
+        Application.EnableVisualStyles() ;
+        Application.SetCompatibleTextRenderingDefault( false ) ;
+        mMainForm = new MainForm() ;
+        Application.Run( mMainForm ) ;
+    }
+
+    public static void showInfoMsg( string msg ) { MessageBox.Show(msg,APP_NAME,MessageBoxButtons.OK,MessageBoxIcon.Information) ; }
+    public static void showWarningMsg( string msg ) { MessageBox.Show(msg,APP_NAME,MessageBoxButtons.OK,MessageBoxIcon.Warning) ; }
+    public static void showErrorMsg( string msg ) { MessageBox.Show(msg,APP_NAME,MessageBoxButtons.OK,MessageBoxIcon.Error) ; }
+
+    public static void logTraceMsg( string msg )
+    {
+        // log a trace message
+        Trace.WriteLine( DateTime.Now.ToString("HH:mm:ss") + " | " + msg ) ;
+    }
+
+    public static JsonConfig appConfig { get { return mAppConfig ; } }
+    public static JsonConfig debugConfig { get { return mDebugConfig ; } }
+    public static string dataDir { get { return mDataDir ; } }
+}