Merge pull request #21 from pauldendulk/fix/concurrent-excepton

Fix concurrent exception

Author: pauldendulk

source/AliFlux/VexTile.Renderers.Mvt.AliFlux/SKColorFactory.cs

@@ -1,4 +1,4 @@
-using System.Collections.Generic;
+using System.Collections.Concurrent;
 using System.Runtime.CompilerServices;
 using SkiaSharp;
 
@@ -7,47 +7,51 @@ namespace VexTile.Renderer.Mvt.AliFlux;
 // ReSharper disable once InconsistentNaming
 public static class SKColorFactory
 {
-    private static readonly Dictionary<string, SKColor> Colours = new();
+    // Use packed ARGB (0xAARRGGBB) as the key to avoid string allocations
+    private static readonly ConcurrentDictionary<uint, SKColor> Colours = new();
 
     // try to centralise this as tracking down where colours ar made is hard
     public static SKColor MakeColor(byte red, byte green, byte blue, byte alpha = 255, [CallerMemberName] string callerName = "<unknown>")
     {
-        string key = MakeKey(red, green, blue, alpha);
+        uint key = MakeKey(red, green, blue, alpha);
 
-        if (!Colours.TryGetValue(key, out SKColor color))
-        {
-            color = new SKColor(red, green, blue, alpha);
-            Colours[key] = color;
+        var color = Colours.GetOrAdd(key, _ => new SKColor(red, green, blue, alpha));
 
 #if DEBUG_COLORS
-            log.Debug($"{callerName} -> Created {key} :: SKColorFactory.MakeColor({red}, {green}, {blue}, {alpha})");
+        var hex = MakeKeyHex(red, green, blue, alpha); // RRGGBBAA for readability
+        log.Debug($"{callerName} -> GetOrAdd {hex} :: SKColorFactory.MakeColor({red}, {green}, {blue}, {alpha})");
 #endif
-        }
-        else
-        {
-#if DEBUG_COLORS
-            log.Debug($"{callerName} -> Got {key} :: SKColorFactory.MakeColor");
-#endif
-        }
 
         return color;
     }
 
-    private static string MakeKey(byte red, byte green, byte blue, byte alpha)
+    private static uint MakeKey(byte red, byte green, byte blue, byte alpha)
     {
-        string key = $"{red:x2}{green:x2}{blue:x2}{alpha:x2}";
-        return key;
+        // ARGB packed to match SKColor's internal layout
+        return ((uint)alpha << 24) | ((uint)red << 16) | ((uint)green << 8) | blue;
     }
 
-    // make logging colors simpler
+#if DEBUG_COLORS
+    // Keep previous readable logging format (RRGGBBAA)
+    private static string MakeKeyHex(byte red, byte green, byte blue, byte alpha)
+    {
+        return $"{red:x2}{green:x2}{blue:x2}{alpha:x2}";
+    }
+#endif
+
+    // Make logging colors simpler
     public static SKColor LogColor(SKColor color, [CallerMemberName] string callerName = "<unknown>")
     {
-        string key = MakeKey(color.Red, color.Green, color.Blue, color.Alpha);
+        // Use the packed ARGB from the color directly
+        uint key = (uint)color;
+
+        _ = Colours.TryAdd(key, color);
+
+#if DEBUG_COLORS
+        var hex = MakeKeyHex(color.Red, color.Green, color.Blue, color.Alpha);
+        log.Debug($"{callerName} -> Log {hex} :: SKColorFactory.LogColor");
+#endif
 
-        if (!Colours.TryGetValue(key, out _))
-        {
-            Colours.Add(key, color);
-        }
         return color;
     }
 }