Reuse shaders/paint where possible

Added noise test

src/Artemis.Plugins.LayerElements.Noise/NoiseLayerElement.cs

@@ -0,0 +1,59 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Artemis.Core.Models.Profile;
+using Artemis.Core.Models.Surface;
+using Artemis.Core.Plugins.LayerElement;
+using SkiaSharp;
+
+namespace Artemis.Plugins.LayerElements.Noise
+{
+    public class NoiseLayerElement : LayerElement
+    {
+        private SKShader _shader;
+        private List<SKColor> _testColors;
+        private SKPaint _paint;
+
+        public NoiseLayerElement(Layer layer, Guid guid, NoiseLayerElementSettings settings, LayerElementDescriptor descriptor) : base(layer, guid, settings, descriptor)
+        {
+            Settings = settings;
+
+            _testColors = new List<SKColor>();
+            for (var i = 0; i < 9; i++)
+            {
+                if (i != 8)
+                    _testColors.Add(SKColor.FromHsv(i * 32, 100, 100));
+                else
+                    _testColors.Add(SKColor.FromHsv(0, 100, 100));
+            }
+
+            CreateShader();
+            Layer.RenderPropertiesUpdated += (sender, args) => CreateShader();
+            Settings.PropertyChanged += (sender, args) => CreateShader();
+        }
+
+        private void CreateShader()
+        {
+            var shader = SKShader.CreatePerlinNoiseFractalNoise(1, 1, 1, 1);
+
+            var oldShader = _shader;
+            var oldPaint = _paint;
+            _shader = shader;
+            _paint = new SKPaint {Shader = _shader, FilterQuality = SKFilterQuality.Low};
+            oldShader?.Dispose();
+            oldPaint?.Dispose();
+        }
+
+        public new NoiseLayerElementSettings Settings { get; }
+
+        public override LayerElementViewModel GetViewModel()
+        {
+            return new NoiseLayerElementViewModel(this);
+        }
+
+        public override void Render(ArtemisSurface surface, SKCanvas canvas)
+        {
+            canvas.DrawRect(Layer.AbsoluteRenderRectangle, _paint);
+        }
+    }
+}