Flicker-free dimming slider for OLED models (#2109)

* Gamma Init

* Cleanup

* Show flicker-free dimming only on supported models

* Gamma ramp tweaks

* Gamma improvements

* Stronger dimming

* Added OLED model detection

app/Display/GammaRamp.cs

@@ -0,0 +1,56 @@
+using System.Runtime.InteropServices;
+
+namespace GHelper.Display
+{
+
+    [StructLayout(LayoutKind.Sequential)]
+    internal struct GammaRamp
+    {
+        public const int DataPoints = 256;
+
+        [MarshalAs(UnmanagedType.ByValArray, SizeConst = DataPoints)]
+        public readonly ushort[] Red;
+        [MarshalAs(UnmanagedType.ByValArray, SizeConst = DataPoints)]
+        public readonly ushort[] Green;
+        [MarshalAs(UnmanagedType.ByValArray, SizeConst = DataPoints)]
+        public readonly ushort[] Blue;
+
+        public GammaRamp(ushort[] red, ushort[] green, ushort[] blue)
+        {
+            if (red == null)
+            {
+                throw new ArgumentNullException(nameof(red));
+            }
+
+            if (green == null)
+            {
+                throw new ArgumentNullException(nameof(green));
+            }
+
+            if (blue == null)
+            {
+                throw new ArgumentNullException(nameof(blue));
+            }
+
+            if (red.Length != DataPoints)
+            {
+                throw new ArgumentOutOfRangeException(nameof(red));
+            }
+
+            if (green.Length != DataPoints)
+            {
+                throw new ArgumentOutOfRangeException(nameof(green));
+            }
+
+            if (blue.Length != DataPoints)
+            {
+                throw new ArgumentOutOfRangeException(nameof(blue));
+            }
+
+            Red = red;
+            Green = green;
+            Blue = blue;
+        }
+    }
+
+}