VolumeSlider.cs

using System.ComponentModel;
using System.Globalization;

namespace ToneGenerator
{
	/// <summary>
	/// Tweaked volume slider that is double buffered and fixes divide by 0 bug on Windows XP.
	/// </summary>
	public class VolumeSlider : UserControl
	{
		/// <summary>
		/// Creates a new VolumeSlider control.
		/// </summary>
		public VolumeSlider()
		{
			Name = "VolumeSlider";
			Size = new Size(96, 16);
		}

		/// <summary>
		/// The volume for this control.
		/// </summary>
		private float volume = 1f;
		[DefaultValue(1f)]
		public float Volume
		{
			get { return volume; }
			set
			{
				if (value < 0f)
					value = 0f;
				if (value > Utilities.DbToMag(maximumDB))
					value = Utilities.DbToMag(maximumDB);
				if (volume != value)
				{
					volume = value;
					if (VolumeChanged != null)
						VolumeChanged(this, EventArgs.Empty);
					Invalidate();
				}
			}
		}

		private float minimumDB = -60;
		/// <summary>
		/// Gets or sets the minimum decibel volume for the control.
		/// </summary>
		public float MinimumDB
		{
			get { return minimumDB; }
			set
			{
				minimumDB = value;
				Invalidate();
			}
		}

		private float maximumDB = 0;
		/// <summary>
		/// Gets or sets the minimum decibel volume for the control.
		/// </summary>
		public float MaximumDB
		{
			get { return maximumDB; }
			set
			{
				maximumDB = value;
				Invalidate();
			}
		}

		/// <summary>
		/// Volume changed event
		/// </summary>
		public event EventHandler? VolumeChanged;

		/// <summary>
		/// Raises the <see cref="HandleCreated"/> event.
		/// </summary>
		/// <param name="e">An <see cref="EventArgs"/> that contains the event data.</param>
		protected override void OnHandleCreated(EventArgs e)
		{
			base.OnHandleCreated(e);

			DoubleBuffered = true;
		}

		/// <summary>
		/// <see cref="M:System.Windows.Forms.Control.OnMouseDown(System.Windows.Forms.MouseEventArgs)" />
		/// </summary>
		protected override void OnMouseDown(MouseEventArgs e)
		{
			SetVolumeFromMouse(e.X);
			base.OnMouseDown(e);
		}

		/// <summary>
		/// <see cref="M:System.Windows.Forms.Control.OnMouseMove(System.Windows.Forms.MouseEventArgs)" />
		/// </summary>
		protected override void OnMouseMove(MouseEventArgs e)
		{
			if (e.Button == MouseButtons.Left)
				SetVolumeFromMouse(e.X);
			base.OnMouseMove(e);
		}

		/// <summary>
		/// Raises the <see cref="Resize"/> event.
		/// </summary>
		/// <param name="e">An System.EventArgs that contains the event data.</param>
		protected override void OnResize(EventArgs e)
		{
			base.OnResize(e);
			Invalidate();
		}

		/// <summary>
		/// Raises the <see cref="Paint"/> event.
		/// </summary>
		/// <param name="pe">A <see cref="PaintEventArgs"/> that contains the event data.</param>
		protected override void OnPaint(PaintEventArgs pe)
		{
			base.OnPaint(pe);

			pe.Graphics.DrawRectangle(Pens.Black, 0, 0, Width - 1, Height - 1);
			float db = Utilities.MagToDb(volume);
			float fraction = 1f - (db - maximumDB) / (minimumDB - maximumDB);
			int width = (int)((Width - 2) * fraction);
			pe.Graphics.FillRectangle(Brushes.LightGreen, 1, 1, Math.Max(0, width), Height - 2);
			using (var stringFormat = new StringFormat { LineAlignment = StringAlignment.Center, Alignment = StringAlignment.Center })
			{
				pe.Graphics.DrawString(string.Format(CultureInfo.CurrentCulture, "{0:F2} dB", db), Font, Brushes.Black, ClientRectangle, stringFormat);
			}
		}

		private void SetVolumeFromMouse(int x)
		{
			Volume = x <= 0 ? 0f : Utilities.DbToMag(maximumDB + (1f - (float)x / (Width - 2)) * (minimumDB - maximumDB));
		}
	}
}