From 9ed01c29ba8cccd840021fd10f652c77c59a6d07 Mon Sep 17 00:00:00 2001
From: Glenn Maynard <glenn@steprevolution.com>
Date: Sat, 21 Apr 2018 02:26:40 -0500
Subject: [PATCH] Implement exporting and importing platform settings to a
 file.

---
 smx-config/Helpers.cs         | 184 ++++++++++++
 smx-config/MainWindow.xaml    |  10 +
 smx-config/MainWindow.xaml.cs |  51 ++++
 smx-config/SMX.cs             |  17 ++
 smx-config/SMXConfig.csproj   |   1 +
 smx-config/SMXJSON.cs         | 531 ++++++++++++++++++++++++++++++++++
 smx-config/Widgets.cs         |  74 +----
 7 files changed, 808 insertions(+), 60 deletions(-)
 create mode 100644 smx-config/SMXJSON.cs

diff --git a/smx-config/Helpers.cs b/smx-config/Helpers.cs
index 656d66d..9cdf7fc 100644
--- a/smx-config/Helpers.cs
+++ b/smx-config/Helpers.cs
@@ -3,6 +3,7 @@ using System.Collections.Generic;
 using System.Linq;
 using System.Windows.Media;
 using System.Windows.Threading;
+using SMXJSON;
 
 namespace smx_config
 {
@@ -37,6 +38,62 @@ namespace smx_config
             return Color.FromRgb(R, G, B);
         }
 
+        // Return a Color as an HTML color code.
+        public static string ColorToString(Color color)
+        {
+            // WPF's Color.ToString() returns #AARRGGBB, which is just wrong.  Alpha is always
+            // last in HTML color codes.  We don't need alpha, so just strip it off.
+            return "#" + color.ToString().Substring(3);
+        }
+
+        // Parse #RRGGBB and return a Color, or white if the string isn't in the correct format.
+        public static Color ParseColorString(string s)
+        {
+            // We only expect "#RRGGBB".
+            if(s.Length != 7 || !s.StartsWith("#"))
+                return Color.FromRgb(255,255,255);
+
+            try {
+                return (Color) ColorConverter.ConvertFromString(s);
+            }
+            catch(System.FormatException)
+            {
+                return Color.FromRgb(255,255,255);
+            }
+        }
+
+        // Light values are actually in the range 0-170 and not 0-255, since higher values aren't
+        // any brighter and just draw more power.  The auto-lighting colors that we're configuring
+        // need to be scaled to this range too, but show full range colors in the UI.
+        readonly static double LightsScaleFactor = 0.666666f;
+        static public Byte ScaleColor(Byte c)
+        {
+            return (Byte) Math.Round(c * LightsScaleFactor);
+        }
+        static public Byte UnscaleColor(Byte c)
+        {
+            Byte result = (Byte) Math.Round(Math.Min(255, c / LightsScaleFactor));
+
+            // The color values we output are quantized, since we're scaling an 8-bit value.
+            // This doesn't have any real effect, but it causes #FFFFFF in the settings export
+            // file to be written out as #FDFDFD (which has the same value in hardware).  Just
+            // so the common value of white is clean, snap these values to 0xFF.  The end result
+            // will be the same.
+            if(result >= 0xFD)
+                return 0xFF;
+            return result;
+        }
+
+        static public Color ScaleColor(Color c)
+        {
+            return Color.FromRgb(ScaleColor(c.R), ScaleColor(c.G), ScaleColor(c.B));
+        }
+
+        static public Color UnscaleColor(Color c)
+        {
+            return Color.FromRgb(UnscaleColor(c.R), UnscaleColor(c.G), UnscaleColor(c.B));
+        }
+
         public static Color FromHSV(double H, double S, double V)
         {
             H = H % 360;
@@ -96,6 +153,18 @@ namespace smx_config
             s = C / M;
             v = M;
         }
+
+        // Read path.  If an error is encountered, return "".
+        public static string ReadFile(string path)
+        {
+            try {
+                return System.IO.File.ReadAllText(path);
+            }
+            catch(System.IO.IOException)
+            {
+                return "";
+            }
+        }
     }
 
     // This class just makes it easier to assemble binary command packets.
@@ -201,4 +270,119 @@ namespace smx_config
             SMX.SMX.SetLights(cmd.Get());
         }
     };
+
+    static class SMXHelpers
+    {
+        // Export configurable values in SMXConfig to a JSON string.
+        public static string ExportSettingsToJSON(SMX.SMXConfig config)
+        {
+            Dictionary<string, Object> dict = new Dictionary<string, Object>();
+            List<int> panelLowThresholds = new List<int>();
+            panelLowThresholds.Add(config.panelThreshold0Low);
+            panelLowThresholds.Add(config.panelThreshold1Low);
+            panelLowThresholds.Add(config.panelThreshold2Low);
+            panelLowThresholds.Add(config.panelThreshold3Low);
+            panelLowThresholds.Add(config.panelThreshold4Low);
+            panelLowThresholds.Add(config.panelThreshold5Low);
+            panelLowThresholds.Add(config.panelThreshold6Low);
+            panelLowThresholds.Add(config.panelThreshold7Low);
+            panelLowThresholds.Add(config.panelThreshold8Low);
+            dict.Add("panelLowThresholds", panelLowThresholds);
+
+            List<int> panelHighThresholds = new List<int>();
+            panelHighThresholds.Add(config.panelThreshold0High);
+            panelHighThresholds.Add(config.panelThreshold1High);
+            panelHighThresholds.Add(config.panelThreshold2High);
+            panelHighThresholds.Add(config.panelThreshold3High);
+            panelHighThresholds.Add(config.panelThreshold4High);
+            panelHighThresholds.Add(config.panelThreshold5High);
+            panelHighThresholds.Add(config.panelThreshold6High);
+            panelHighThresholds.Add(config.panelThreshold7High);
+            panelHighThresholds.Add(config.panelThreshold8High);
+            dict.Add("panelHighThresholds", panelHighThresholds);
+
+            // Store the enabled panel mask as a simple list of which panels are selected.
+            bool[] enabledPanels = config.GetEnabledPanels();
+            List<int> enabledPanelList = new List<int>();
+            for(int panel = 0; panel < 9; ++panel)
+            {
+                if(enabledPanels[panel])
+                    enabledPanelList.Add(panel);
+            }
+            dict.Add("enabledPanels", enabledPanelList);
+
+            // Store panel colors.
+            List<string> panelColors = new List<string>();
+            for(int PanelIndex = 0; PanelIndex < 9; ++PanelIndex)
+            {
+                // Scale colors from the hardware value back to the 0-255 value we use in the UI.
+                Color color = Color.FromRgb(config.stepColor[PanelIndex*3+0], config.stepColor[PanelIndex*3+1], config.stepColor[PanelIndex*3+2]);
+                color = Helpers.UnscaleColor(color);
+                panelColors.Add(Helpers.ColorToString(color));
+            }
+            dict.Add("panelColors", panelColors);
+
+            return SMXJSON.SerializeJSON.Serialize(dict);
+        }
+
+        // Import a saved JSON configuration to an SMXConfig.
+        public static void ImportSettingsFromJSON(string json, ref SMX.SMXConfig config)
+        {
+            Dictionary<string, Object> dict = SMXJSON.ParseJSON.Parse<Dictionary<string, Object>>(json);
+
+            // Read the thresholds.  If any values are missing, we'll leave the value in config alone.
+            List<Object> newPanelLowThresholds = dict.Get("panelLowThresholds", new List<Object>());
+            config.panelThreshold0Low = newPanelLowThresholds.Get(0, config.panelThreshold0Low);
+            config.panelThreshold1Low = newPanelLowThresholds.Get(1, config.panelThreshold1Low);
+            config.panelThreshold2Low = newPanelLowThresholds.Get(2, config.panelThreshold2Low);
+            config.panelThreshold3Low = newPanelLowThresholds.Get(3, config.panelThreshold3Low);
+            config.panelThreshold4Low = newPanelLowThresholds.Get(4, config.panelThreshold4Low);
+            config.panelThreshold5Low = newPanelLowThresholds.Get(5, config.panelThreshold5Low);
+            config.panelThreshold6Low = newPanelLowThresholds.Get(6, config.panelThreshold6Low);
+            config.panelThreshold7Low = newPanelLowThresholds.Get(7, config.panelThreshold7Low);
+            config.panelThreshold8Low = newPanelLowThresholds.Get(8, config.panelThreshold8Low);
+
+            List<Object> newPanelHighThresholds = dict.Get("panelHighThresholds", new List<Object>());
+            config.panelThreshold0High = newPanelHighThresholds.Get(0, config.panelThreshold0High);
+            config.panelThreshold1High = newPanelHighThresholds.Get(1, config.panelThreshold1High);
+            config.panelThreshold2High = newPanelHighThresholds.Get(2, config.panelThreshold2High);
+            config.panelThreshold3High = newPanelHighThresholds.Get(3, config.panelThreshold3High);
+            config.panelThreshold4High = newPanelHighThresholds.Get(4, config.panelThreshold4High);
+            config.panelThreshold5High = newPanelHighThresholds.Get(5, config.panelThreshold5High);
+            config.panelThreshold6High = newPanelHighThresholds.Get(6, config.panelThreshold6High);
+            config.panelThreshold7High = newPanelHighThresholds.Get(7, config.panelThreshold7High);
+            config.panelThreshold8High = newPanelHighThresholds.Get(8, config.panelThreshold8High);
+
+            List<Object> enabledPanelList = dict.Get<List<Object>>("enabledPanels", null);
+            if(enabledPanelList != null)
+            {
+                bool[] enabledPanels = new bool[9];
+                for(int i = 0; i < enabledPanelList.Count; ++i)
+                {
+                    int panel = enabledPanelList.Get(i, 0);
+
+                    // Sanity check:
+                    if(panel < 0 || panel >= 9)
+                        continue;
+                    enabledPanels[panel] = true;
+                }
+                config.SetEnabledPanels(enabledPanels);
+            }
+
+            List<Object> panelColors = dict.Get<List<Object>>("panelColors", null);
+            if(panelColors != null)
+            {
+                for(int PanelIndex = 0; PanelIndex < 9 && PanelIndex < panelColors.Count; ++PanelIndex)
+                {
+                    string colorString = panelColors.Get(PanelIndex, "#FFFFFF");
+                    Color color = Helpers.ParseColorString(colorString);
+                    color = Helpers.ScaleColor(color);
+
+                    config.stepColor[PanelIndex*3+0] = color.R;
+                    config.stepColor[PanelIndex*3+1] = color.G;
+                    config.stepColor[PanelIndex*3+2] = color.B;
+                }
+            }
+        }
+    };
 }
diff --git a/smx-config/MainWindow.xaml b/smx-config/MainWindow.xaml
index 106bf79..3883f5f 100644
--- a/smx-config/MainWindow.xaml
+++ b/smx-config/MainWindow.xaml
@@ -781,6 +781,16 @@ Input will be disabled from deselected panels.</TextBlock>
                         <controls:PanelSelector Focusable="false" />
                     </StackPanel>
 
+                    <Separator Margin="0,10,0,10" />
+                    <TextBlock HorizontalAlignment="Center"
+                        xml:space="preserve" FontSize="16">Import/export settings</TextBlock>
+                    <TextBlock xml:space="preserve" HorizontalAlignment="Center" Margin="0,5,0,0" TextAlignment="Center"
+                               >Export current settings to a file.</TextBlock>
+                    <StackPanel Orientation="Horizontal" HorizontalAlignment="Center">
+                        <Button Content="Export" Width="50" Padding="5,2" Margin="5,10" Click="ExportSettings" />
+                        <Button Content="Import" Width="50" Padding="5,2" Margin="5,10" Click="ImportSettings" />
+                    </StackPanel>
+
                     <Separator Margin="0,10,0,10" />
                     <TextBlock HorizontalAlignment="Center"
                                    xml:space="preserve" FontSize="16">Reset all settings</TextBlock>
diff --git a/smx-config/MainWindow.xaml.cs b/smx-config/MainWindow.xaml.cs
index bc72ba8..c8a137f 100644
--- a/smx-config/MainWindow.xaml.cs
+++ b/smx-config/MainWindow.xaml.cs
@@ -82,5 +82,56 @@ namespace smx_config
                 SMX.SMX.FactoryReset(pad);
             CurrentSMXDevice.singleton.FireConfigurationChanged(null);
         }
+
+        private void ExportSettings(object sender, RoutedEventArgs e)
+        {
+            // Save the current thresholds on the first available pad as a preset.
+            for(int pad = 0; pad < 2; ++pad)
+            {
+                SMX.SMXConfig config;
+                if(!SMX.SMX.GetConfig(pad, out config))
+                    continue;
+
+                string json = SMXHelpers.ExportSettingsToJSON(config);
+
+                Microsoft.Win32.SaveFileDialog dialog = new Microsoft.Win32.SaveFileDialog();
+                dialog.FileName = "StepManiaX settings";
+                dialog.DefaultExt = ".smxcfg";
+                dialog.Filter = "StepManiaX settings (.smxcfg)|*.smxcfg";
+                bool? result = dialog.ShowDialog();
+                if(result == null || !(bool) result)
+                    return;
+
+                System.IO.File.WriteAllText(dialog.FileName, json);
+                return;
+            }
+        }
+
+        private void ImportSettings(object sender, RoutedEventArgs e)
+        {
+            // Prompt for a file to read.
+            Microsoft.Win32.OpenFileDialog dialog = new Microsoft.Win32.OpenFileDialog();
+            dialog.FileName = "StepManiaX settings";
+            dialog.DefaultExt = ".smxcfg";
+            dialog.Filter = "StepManiaX settings (.smxcfg)|*.smxcfg";
+            bool? result = dialog.ShowDialog();
+            if(result == null || !(bool) result)
+                return;
+
+            string json = Helpers.ReadFile(dialog.FileName);
+
+            // Apply settings from the file to all connected pads.
+            for(int pad = 0; pad < 2; ++pad)
+            {
+                SMX.SMXConfig config;
+                if(!SMX.SMX.GetConfig(pad, out config))
+                    continue;
+
+                SMXHelpers.ImportSettingsFromJSON(json, ref config);
+                SMX.SMX.SetConfig(pad, config);
+            }
+
+            CurrentSMXDevice.singleton.FireConfigurationChanged(null);
+        }
     }
 } 
diff --git a/smx-config/SMX.cs b/smx-config/SMX.cs
index fddba65..88bbcac 100644
--- a/smx-config/SMX.cs
+++ b/smx-config/SMX.cs
@@ -76,6 +76,23 @@ namespace SMX
                 (enabledSensors[4] & 0xF0) != 0,
             };
         }
+
+        // Set enabledSensors from an array returned from GetEnabledPanels.
+        public void SetEnabledPanels(bool[] panels)
+        {
+            for(int i = 0; i < 5; ++i)
+                enabledSensors[i] = 0;
+
+            if(panels[0]) enabledSensors[0] |= 0xF0;
+            if(panels[1]) enabledSensors[0] |= 0x0F;
+            if(panels[2]) enabledSensors[1] |= 0xF0;
+            if(panels[3]) enabledSensors[1] |= 0x0F;
+            if(panels[4]) enabledSensors[2] |= 0xF0;
+            if(panels[5]) enabledSensors[2] |= 0x0F;
+            if(panels[6]) enabledSensors[3] |= 0xF0;
+            if(panels[7]) enabledSensors[3] |= 0x0F;
+            if(panels[8]) enabledSensors[4] |= 0xF0;
+        }
     };  
 
     public struct SMXSensorTestModeData
diff --git a/smx-config/SMXConfig.csproj b/smx-config/SMXConfig.csproj
index 72ab963..7ba7d65 100644
--- a/smx-config/SMXConfig.csproj
+++ b/smx-config/SMXConfig.csproj
@@ -103,6 +103,7 @@
     <Compile Include="DiagnosticsWidgets.cs" />
     <Compile Include="DoubleSlider.cs" />
     <Compile Include="Helpers.cs" />
+    <Compile Include="SMXJSON.cs" />
     <Compile Include="SMX.cs" />
     <Compile Include="Widgets.cs" />
     <Page Include="MainWindow.xaml">
diff --git a/smx-config/SMXJSON.cs b/smx-config/SMXJSON.cs
new file mode 100644
index 0000000..51ede86
--- /dev/null
+++ b/smx-config/SMXJSON.cs
@@ -0,0 +1,531 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Text;
+
+// All C# JSON implementations are either pretty awful or incredibly bloated, so we
+// just use our own.
+namespace SMXJSON
+{
+    public class JSONError: Exception
+    {
+        public JSONError(string error)
+        {
+        }
+    };
+
+    public class ParseError: JSONError
+    {
+        public ParseError(StringReader reader, string error):
+            base(error)
+        {
+        }
+    };
+
+    public static class ObjectListExtensions
+    {
+        public static T Get<T>(this List<object> array, int idx, T defaultValue)
+        {
+            if(idx < 0 || idx >= array.Count)
+                return defaultValue;
+
+            object value = array[idx];
+            if(!typeof(T).IsAssignableFrom(value.GetType()))
+                return defaultValue;
+
+            return (T) value;
+        }
+
+        // Our numbers are always doubles.  Add some other basic data types for convenience.
+        public static int Get(this List<object> array, int idx, int defaultValue)
+        {
+            return (int) array.Get(idx, (double) defaultValue);
+        }
+
+        public static Byte Get(this List<object> array, int idx, Byte defaultValue)
+        {
+            return (Byte) array.Get(idx, (double) defaultValue);
+        }
+
+        public static float Get(this List<object> array, int idx, float defaultValue)
+        {
+            return (float) array.Get(idx, (double) defaultValue);
+        }
+
+        // Return the value of key.  If it doesn't exist, or doesn't have the expected
+        // type, return defaultValue.
+        public static T Get<T>(this Dictionary<string, Object> dict, string key, T defaultValue)
+        {
+            object value;
+            if(!dict.TryGetValue(key, out value))
+                return defaultValue;
+
+            if(!typeof(T).IsAssignableFrom(value.GetType()))
+                return defaultValue;
+
+            return (T) value;
+        }
+
+        // Set result to the value of key if it exists and has the correct type, and return
+        // true.  Otherwise, leave result unchanged and return false.
+        public static bool GetValue<T>(this Dictionary<string, Object> dict, string key, ref T result)
+        {
+            object value;
+            if(!dict.TryGetValue(key, out value))
+                return false;
+
+            if(!typeof(T).IsAssignableFrom(result.GetType()))
+                return false;
+
+            result = (T) value;
+            return true;
+        }
+
+        // Our numbers are always doubles.  Add some other basic data types for convenience.
+        public static int Get(this Dictionary<string, Object> dict, string key, int defaultValue)
+        {
+            return (int) dict.Get(key, (double) defaultValue);
+        }
+
+        public static Byte Get(this Dictionary<string, Object> dict, string key, Byte defaultValue)
+        {
+            return (Byte) dict.Get(key, (double) defaultValue);
+        }
+
+        public static float Get(this Dictionary<string, Object> dict, string key, float defaultValue)
+        {
+            return (float) dict.Get(key, (double) defaultValue);
+        }
+    }
+
+    class SerializeJSON
+    {
+        static public string Serialize(object obj)
+        {
+            StringBuilder output = new StringBuilder();
+            Serialize(obj, output, 0);
+            output.Append('\n');
+            return output.ToString();
+        }
+
+        // Add start-of-line indentation.
+        static private void AddIndent(StringBuilder output, int indent)
+        {
+            output.Append(' ', indent*4);
+        }
+
+        // Serialize a boolean.
+        static private void SerializeObject(bool value, StringBuilder output)
+        {
+            if(value)
+                output.Append("true");
+            else
+                output.Append("false");
+        }
+
+        // Serialize a string.
+        static private void SerializeObject(String str, StringBuilder output)
+        {
+            output.Append('"');
+
+            foreach(char c in str)
+            {
+                switch(c)
+                {
+                case '"': output.Append("\\\""); break;
+                case '\\': output.Append("\\\\"); break;
+                case '\b': output.Append("\\b"); break;
+                case '\n': output.Append("\\n"); break;
+                case '\r': output.Append("\\r"); break;
+                case '\t': output.Append("\\t"); break;
+                default:
+                    // We don't escape Unicode.  Every sane JSON parser accepts UTF-8.
+                    output.Append(c);
+                    break;
+                }
+            }
+
+            output.Append('"');
+        }
+
+        // Serialize an array.
+        static private void SerializeObject<T>(List<T> array, StringBuilder output, int indent)
+        {
+            output.Append("[\n");
+            bool first = true;
+            indent += 1;
+            foreach(T element in array)
+            {
+                if(first)
+                    first = false;
+                else
+                    output.Append(",\n");
+
+                AddIndent(output, indent);
+                Serialize(element, output, indent);
+            }
+            output.Append('\n');
+
+            indent -= 1;
+            AddIndent(output, indent);
+            output.Append(']');
+        }
+
+        // Serialize a dictionary.
+        static private void SerializeObject<T>(Dictionary<string, T> dict, StringBuilder output, int indent)
+        {
+            output.Append("{\n");
+
+            indent += 1;
+            bool first = true;
+            foreach(KeyValuePair<string,T> element in dict)
+            {
+                if(first)
+                    first = false;
+                else
+                    output.Append(",\n");
+
+                AddIndent(output, indent);
+                SerializeObject(element.Key, output);
+                output.Append(':');
+                output.Append(' ');
+                Serialize(element.Value, output, indent);
+            }
+            output.Append('\n');
+
+            indent -= 1;
+            AddIndent(output, indent);
+            output.Append('}');
+        }
+        
+        // Serialize an object based on its type.
+        static public void Serialize(object obj, StringBuilder output, int indent)
+        {
+            if(obj == null) { output.Append("null"); return; }
+
+            if(typeof(Int32).IsInstanceOfType(obj)) { output.Append(obj.ToString()); return; }
+            if(typeof(float).IsInstanceOfType(obj)) { output.Append(obj.ToString()); return; }
+            if(typeof(Double).IsInstanceOfType(obj)) { output.Append(obj.ToString()); return; }
+
+            if(typeof(Boolean).IsInstanceOfType(obj)) { SerializeObject((Boolean) obj, output); return; }
+            if(typeof(string).IsInstanceOfType(obj)) { SerializeObject((string) obj, output); return; }
+
+            // C# generics aren't very well designed, so this is clunky.  We should be able to cast
+            // a List<string> to List<object>, but some overzealous language designers thought that
+            // since that has some unsafe uses, we shouldn't be allowed to use it for perfectly safe
+            // uses either (eg. read-only access).
+            if(obj.GetType().GetGenericTypeDefinition().IsAssignableFrom(typeof(List<>)))
+            {
+                Type valueType = obj.GetType().GetGenericArguments()[0];
+                if(valueType == typeof(object)) { SerializeObject((List<object>)obj, output, indent); return; }
+                if(valueType == typeof(Int32)) { SerializeObject((List<Int32>)obj, output, indent); return; }
+                if(valueType == typeof(float)) { SerializeObject((List<float>)obj, output, indent); return; }
+                if(valueType == typeof(Double)) { SerializeObject((List<Double>)obj, output, indent); return; }
+                if(valueType == typeof(Boolean)) { SerializeObject((List<Boolean>)obj, output, indent); return; }
+                if(valueType == typeof(string)) { SerializeObject((List<string>)obj, output, indent); return; }
+            }
+
+            if(obj.GetType().GetGenericTypeDefinition().IsAssignableFrom(typeof(Dictionary<,>)))
+            {
+                Type keyType = obj.GetType().GetGenericArguments()[0];
+                if(typeof(string).IsAssignableFrom(keyType))
+                {
+                    Type valueType = obj.GetType().GetGenericArguments()[1];
+                    if(valueType == typeof(object)) { SerializeObject((Dictionary<string, object>)obj, output, indent); return; }
+                    if(valueType == typeof(Int32)) { SerializeObject((Dictionary<string, Int32>)obj, output, indent); return; }
+                    if(valueType == typeof(float)) { SerializeObject((Dictionary<string, float>)obj, output, indent); return; }
+                    if(valueType == typeof(Double)) { SerializeObject((Dictionary<string, Double>)obj, output, indent); return; }
+                    if(valueType == typeof(Boolean)) { SerializeObject((Dictionary<string, Boolean>)obj, output, indent); return; }
+                    if(valueType == typeof(string)) { SerializeObject((Dictionary<string, string>)obj, output, indent); return; }
+                }
+            }
+
+            throw new JSONError("Unsupported type: " + obj.GetType());
+        }
+    }
+
+    class ParseJSON
+    {
+        static private void SkipWhitespace(StringReader reader)
+        {
+            while(true)
+            {
+                int c = reader.Peek();
+                switch(c)
+                {
+                case ' ':
+                case '\n':
+                case '\t':
+                    reader.Read();
+                    continue;
+                default:
+                    return;
+                }
+            }
+        }
+
+        // Parse JSON.  On error, return null.
+        public static Object Parse(string json)
+        {
+            return ParseWithExceptions(new StringReader(json));
+        }
+
+        // Parse JSON, expecting a specific outer type.  On parse error, return a default value.
+        public static T Parse<T>(string json) where T: new()
+        {
+            Object result = Parse(json);
+            if(!typeof(T).IsAssignableFrom(result.GetType()))
+                return new T();
+            return (T) result;
+        }
+
+        // Parse JSON.  On error, raise JSONError.
+        //
+        // Most of the time, errors aren't expected and putting exception handling around every
+        // place JSON is parsed can be brittle.  Parse() can be used instead to just return
+        // a default value.
+        public static Object ParseWithExceptions(StringReader reader)
+        {
+            Object result = ParseJSONValue(reader);
+
+            SkipWhitespace(reader);
+
+            // Other than whitespace, we should be at the end of the file.
+            if(reader.Read() != -1)
+                throw new ParseError(reader, "Unexpected data at the end of the string");
+
+            return result;
+        }
+
+        private static Object ParseJSONValue(StringReader reader)
+        {
+            SkipWhitespace(reader);
+            int nextCharacter = reader.Peek();
+            switch(nextCharacter)
+            {
+            case '"':
+                return ReadJSONString(reader);
+            case '{':
+                return ReadJSONDictionary(reader);
+            case '[':
+                return ReadJSONArray(reader);
+            }
+            if(nextCharacter == '-' || (nextCharacter >= '0' && nextCharacter <= '9'))
+                return ReadJSONNumber(reader);
+
+            if(reader.Peek() == 'n')
+            {
+                // The only valid value this can be is "null".
+                Expect(reader, 'n');
+                Expect(reader, 'u');
+                Expect(reader, 'l');
+                Expect(reader, 'l');
+                return null;
+            }
+
+            if(reader.Peek() == 't')
+            {
+                Expect(reader, 't');
+                Expect(reader, 'r');
+                Expect(reader, 'u');
+                Expect(reader, 'e');
+                return true;
+            }
+
+            if(reader.Peek() == 'f')
+            {
+                Expect(reader, 'f');
+                Expect(reader, 'a');
+                Expect(reader, 'l');
+                Expect(reader, 's');
+                Expect(reader, 'e');
+                return true;
+            }
+
+            throw new ParseError(reader, "Unexpected token");
+        }
+
+        // Skip whitespace, then read one character, which we expect to have a specific value.
+        static private void Expect(StringReader reader, char character)
+        {
+            SkipWhitespace(reader);
+
+            if(reader.Read() != character)
+                throw new ParseError(reader, "Expected " + character);
+        }
+
+        static private List<Object> ReadJSONArray(StringReader reader)
+        {
+            Expect(reader, '[');
+            List<Object> result = new List<Object>();
+            while(true)
+            {
+                Object value = ParseJSONValue(reader);
+                result.Add(value);
+
+                SkipWhitespace(reader);
+                int nextCharacter = reader.Read();
+                switch(nextCharacter)
+                {
+                case ']':
+                    return result;
+                case ',':
+                    continue;
+                case -1:
+                    throw new ParseError(reader, "Unexpected EOF reading array");
+                default:
+                    throw new ParseError(reader, "Unexpected token " + nextCharacter + " reading array");
+                }
+            }
+        }
+        static private Dictionary<string, Object> ReadJSONDictionary(StringReader reader)
+        {
+            Expect(reader, '{');
+
+            Dictionary<string, Object> result = new Dictionary<string, Object>();
+
+            while(true)
+            {
+                string key = ReadJSONString(reader);
+                Expect(reader, ':');
+                Object value = ParseJSONValue(reader);
+                result.Add(key, value);
+
+                SkipWhitespace(reader);
+                switch(reader.Read())
+                {
+                case '}':
+                    return result;
+                case ',':
+                    continue;
+                case -1:
+                    throw new ParseError(reader, "Unexpected EOF reading dictionary");
+                default:
+                    throw new ParseError(reader, "Unexpected token reading dictionary");
+                }
+            }
+        }
+
+        static private string ReadJSONString(StringReader reader)
+        {
+            Expect(reader, '"');
+
+            StringBuilder result = new StringBuilder();
+
+            while(true)
+            {
+                int c = reader.Read();
+                if(c == -1)
+                    throw new ParseError(reader, "Unexpected EOF reading string");
+                if(c == '"')
+                    break;
+
+                // XXX: untested
+                if(c == '\\')
+                {
+                    c = reader.Read();
+                    switch(c)
+                    {
+                    case '"':
+                    case '\\':
+                    case '/':
+                        result.Append((char) c);
+                        break;
+                    case 'b': result.Append('\b'); break;
+                    case 'n': result.Append('\n'); break;
+                    case 'r': result.Append('\r'); break;
+                    case 't': result.Append('\t'); break;
+                    case 'u':
+                    {
+                        // Parse a \u1234 escape.
+                        int codePoint = 0;
+                        for(int i = 0; i < 4; ++i)
+                        {
+                            codePoint *= 10;
+                            c = reader.Read();
+                            if(c == -1)
+                                throw new ParseError(reader, "Unexpected EOF reading string");
+                            if(c < '0' || c > '9')
+                                throw new ParseError(reader, "Unexpected token " + c + " reading Unicode escape");
+                            codePoint += c - (int) '0';
+                        }
+                        result.Append((char) codePoint);
+                        break;
+                    }
+
+                    default:
+                        throw new ParseError(reader, "Unrecognized escape sequence in string: \\" + (char) c);
+                    }
+
+                    continue;
+                }
+
+                result.Append((char) c);
+            }
+
+            return result.ToString();
+        }
+
+        static private double ReadJSONNumber(StringReader reader)
+        {
+            StringBuilder number = new StringBuilder();
+            bool negative = false;
+            if(reader.Peek() == '-')
+            {
+                negative = true;
+                reader.Read();
+            }
+
+            int nextCharacter = reader.Read();
+            if(nextCharacter == '0')
+                number.Append((char) nextCharacter);
+            else
+            {
+                if(nextCharacter < '1' || nextCharacter > '9')
+                    throw new ParseError(reader, "Unexpected token reading number");
+                number.Append((char) nextCharacter);
+
+                while(reader.Peek() >= '0' && reader.Peek() <= '9')
+                    number.Append((char) reader.Read());
+            }
+
+            if(reader.Peek() == '.')
+            {
+                number.Append(reader.Read());
+
+                if(reader.Peek() < '0' || reader.Peek() > '9')
+                    throw new ParseError(reader, "Unexpected token reading number");
+
+                while(reader.Peek() >= '0' && reader.Peek() <= '9')
+                    number.Append((char) reader.Read());
+            }
+
+            if(reader.Peek() == 'e' || reader.Peek() == 'E')
+            {
+                number.Append((char) reader.Read());
+                if(reader.Peek() == '+' || reader.Peek() == '-')
+                    number.Append((char) reader.Read());
+
+                if(reader.Peek() < '0' || reader.Peek() > '9')
+                    throw new ParseError(reader, "Unexpected token reading number");
+
+                while(true)
+                {
+                    nextCharacter = reader.Read();
+                    if(nextCharacter < '0' || nextCharacter > '9')
+                        break;
+                    number.Append((char) nextCharacter);
+                }
+            }
+
+            double result;
+            if(!Double.TryParse(number.ToString(), out result))
+                throw new ParseError(reader, "Unexpected error parsing number \"" + number.ToString() + "\"");
+
+            if(negative)
+                result = -result;
+
+            return result;
+        }
+    }
+}
diff --git a/smx-config/Widgets.cs b/smx-config/Widgets.cs
index 8765995..fa79a78 100644
--- a/smx-config/Widgets.cs
+++ b/smx-config/Widgets.cs
@@ -456,37 +456,13 @@ namespace smx_config
             bool[] enabledPanels = config.GetEnabledPanels();
             Visibility = enabledPanels[PanelIndex]? Visibility.Visible:Visibility.Hidden;
 
-            Color rgb = ColorPicker.UnscaleColor(Color.FromRgb(
+            Color rgb = Helpers.UnscaleColor(Color.FromRgb(
                 config.stepColor[PanelIndex*3+0],
                 config.stepColor[PanelIndex*3+1],
                 config.stepColor[PanelIndex*3+2]));
             PanelColor = new SolidColorBrush(rgb);
         }
 
-        // Return #RRGGBB for the color set on this panel.
-        private string GetColorString()
-        {
-            // WPF's Color.ToString() returns #AARRGGBB, which is just wrong.  Alpha is always
-            // last in HTML color codes.  We don't need alpha, so just strip it off.
-            return "#" + PanelColor.Color.ToString().Substring(3);
-        }
-
-        // Parse #RRGGBB and return a Color, or white if the string isn't in the correct format.
-        private static Color ParseColorString(string s)
-        {
-            // We only expect "#RRGGBB".
-            if(s.Length != 7 || !s.StartsWith("#"))
-                return Color.FromRgb(255,255,255);
-
-            try {
-                return (Color) ColorConverter.ConvertFromString(s);
-            }
-            catch(System.FormatException)
-            {
-                return Color.FromRgb(255,255,255);
-            }
-        }
-
         Point MouseDownPosition;
 
         protected override void OnMouseDown(MouseButtonEventArgs e)
@@ -507,7 +483,7 @@ namespace smx_config
                 if (Math.Abs(position.X - MouseDownPosition.X) >= SystemParameters.MinimumHorizontalDragDistance ||
                     Math.Abs(position.Y - MouseDownPosition.Y) >= SystemParameters.MinimumVerticalDragDistance)
                 {
-                    DragDrop.DoDragDrop(this, GetColorString(), DragDropEffects.Copy);
+                    DragDrop.DoDragDrop(this, Helpers.ColorToString(PanelColor.Color), DragDropEffects.Copy);
                 }
             }
 
@@ -527,7 +503,7 @@ namespace smx_config
                 return false;
 
             // Parse the color being dragged onto us.
-            Color color = ParseColorString(data.GetData(typeof(string)) as string);
+            Color color = Helpers.ParseColorString(data.GetData(typeof(string)) as string);
             
             // Update the panel color.
             int PanelIndex = Panel % 9;
@@ -538,9 +514,10 @@ namespace smx_config
 
             // Light colors are 8-bit values, but we only use values between 0-170.  Higher values
             // don't make the panel noticeably brighter, and just draw more power.
-            config.stepColor[PanelIndex*3+0] = ColorPicker.ScaleColor(color.R);
-            config.stepColor[PanelIndex*3+1] = ColorPicker.ScaleColor(color.G);
-            config.stepColor[PanelIndex*3+2] = ColorPicker.ScaleColor(color.B);
+            color = Helpers.ScaleColor(color);
+            config.stepColor[PanelIndex*3+0] = color.R;
+            config.stepColor[PanelIndex*3+1] = color.G;
+            config.stepColor[PanelIndex*3+2] = color.B;
 
             SMX.SMX.SetConfig(Pad, config);
             CurrentSMXDevice.singleton.FireConfigurationChanged(this);
@@ -664,29 +641,6 @@ namespace smx_config
             });
         }
 
-        // Light values are actually in the range 0-170 and not 0-255, since higher values aren't
-        // any brighter and just draw more power.  The auto-lighting colors that we're configuring
-        // need to be scaled to this range too, but show full range colors in the UI.
-        readonly static double LightsScaleFactor = 0.666666f;
-        static public Byte ScaleColor(Byte c) { return (Byte) (c * LightsScaleFactor); }
-        static public Byte UnscaleColor(Byte c) { return (Byte) Math.Min(255, c / LightsScaleFactor); }
-
-        static public Color ScaleColor(Color c)
-        {
-            return Color.FromRgb(
-                ColorPicker.ScaleColor(c.R),
-                ColorPicker.ScaleColor(c.G),
-                ColorPicker.ScaleColor(c.B));
-        }
-
-        static public Color UnscaleColor(Color c)
-        {
-            return Color.FromRgb(
-                ColorPicker.UnscaleColor(c.R),
-                ColorPicker.UnscaleColor(c.G),
-                ColorPicker.UnscaleColor(c.B));
-        }
-
         private void SaveToConfig()
         {
             if(UpdatingUI)
@@ -707,9 +661,9 @@ namespace smx_config
             // Light colors are 8-bit values, but we only use values between 0-170.  Higher values
             // don't make the panel noticeably brighter, and just draw more power.
             int PanelIndex = SelectedPanel % 9;
-            config.stepColor[PanelIndex*3+0] = ScaleColor(color.R);
-            config.stepColor[PanelIndex*3+1] = ScaleColor(color.G);
-            config.stepColor[PanelIndex*3+2] = ScaleColor(color.B);
+            config.stepColor[PanelIndex*3+0] = Helpers.ScaleColor(color.R);
+            config.stepColor[PanelIndex*3+1] = Helpers.ScaleColor(color.G);
+            config.stepColor[PanelIndex*3+2] = Helpers.ScaleColor(color.B);
 
             SMX.SMX.SetConfig(pad, config);
             CurrentSMXDevice.singleton.FireConfigurationChanged(this);
@@ -723,10 +677,10 @@ namespace smx_config
 
             // Reverse the scaling we applied in SaveToConfig.
             int PanelIndex = SelectedPanel % 9;
-            Color rgb = Color.FromRgb(
-                UnscaleColor(config.stepColor[PanelIndex*3+0]),
-                UnscaleColor(config.stepColor[PanelIndex*3+1]),
-                UnscaleColor(config.stepColor[PanelIndex*3+2]));
+            Color rgb = Helpers.UnscaleColor(Color.FromRgb(
+                config.stepColor[PanelIndex*3+0],
+                config.stepColor[PanelIndex*3+1],
+                config.stepColor[PanelIndex*3+2]));
             double h, s, v;
             Helpers.ToHSV(rgb, out h, out s, out v);