Add a class for fading

(we don't have to implement this multiple times)

VocaluxeLib/CFading.cs

@@ -0,0 +1,64 @@
+#region license
+// This file is part of Vocaluxe.
+// 
+// Vocaluxe is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+// 
+// Vocaluxe is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+// 
+// You should have received a copy of the GNU General Public License
+// along with Vocaluxe. If not, see <http://www.gnu.org/licenses/>.
+#endregion
+
+using System.Diagnostics;
+
+namespace VocaluxeLib
+{
+    public class CFading
+    {
+        private readonly float _FromValue;
+        private readonly float _ToValue;
+        private readonly float _Duration; //in ms
+        private readonly Stopwatch _Timer = new Stopwatch();
+
+        /// <summary>
+        ///     Starts a fading process adjusting between 2 values over a given amount of time
+        /// </summary>
+        /// <param name="fromValue">Start value</param>
+        /// <param name="toValue">Target value</param>
+        /// <param name="duration">Duration of the fading in seconds</param>
+        public CFading(float fromValue, float toValue, float duration)
+        {
+            _FromValue = fromValue;
+            _ToValue = toValue;
+            _Duration = duration * 1000f;
+            _Timer.Start();
+        }
+
+        /// <summary>
+        /// Gets the current value and sets finished
+        /// </summary>
+        /// <param name="finished">Set to whether fading has finished</param>
+        /// <returns>Current value (between from and to values)</returns>
+        public float GetValue(out bool finished)
+        {
+            float result;
+            if (_Timer.ElapsedMilliseconds < _Duration)
+            {
+                result = (_Timer.ElapsedMilliseconds / _Duration) * (_ToValue - _FromValue) + _FromValue;
+                finished = false;
+            }
+            else
+            {
+                result = _ToValue;
+                finished = true;
+            }
+            return result;
+        }
+    }
+}

VocaluxeLib/VocaluxeLib.csproj

@@ -130,6 +130,7 @@
     <Reference Include="System.XML" />
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="CFading.cs" />
     <Compile Include="Extensions.cs" />
     <Compile Include="GlobalSuppressions.cs" />
     <Compile Include="IBasic.cs" />