Introduction

Trackbars and scrollbars are convenient ways of displaying a data range.  The trackbars and scrollbars that ship with Visual Studio .NET, however, are a little lacking in aesthetics.  We at Mycos set out to develop a high-performance dynamic trackbar that tool advantage of the GDI+ api and some of our existing drawing utilities.  The end-result looks something like the following image.  At runtime, of course, it allows you to drag and drop the filled area, just as with any normal trackbar.  The value property is public and can be used to get the current setting at any time.

Method #1: DrawBar

This method does the bulk of the heavy lifting with a little help from the DrawingUtils class.  Both classes are included in the sample source.  The properties that are exposed control through the property grid include control color, anti-aliasing, and max and min values.

private void DrawBar(Graphics g, Color foreColor)
{
bool outLine = this.outLineColor != Color.Transparent;
Rectangle bound = this.ClientRectangle;
bound.Inflate(-20, -20);
Mycos.Glib.DrawingUtils.FillCylinder(g, bound, new Size(4, 10),
Color.FromArgb(this.Alpha, foreColor), this.OutLineColor, outLine);
if ( this.Value > this.Minimum && this.Value <= this.Maximum )
{
float barValue = bound.Height * (( this.Value - this.Minimum )
/ ( this.Maximum - this.Minimum));
RectangleF valueBound = RectangleF.FromLTRB(bound.Left,
bound.Bottom - barValue, bound.Right, bound.Bottom); Mycos.Glib.DrawingUtils.FillCylinder(g, valueBound, new Size(4, 10), Color.FromArgb(this.Alpha, this.BarColor), this.OutLineColor, outLine);
if ( this.showValue && valueBound.Height > 20 )
{
g.SmoothingMode = SmoothingMode.AntiAlias;
StringFormat format = new StringFormat();
format.Alignment = StringAlignment.Far;
format.LineAlignment = StringAlignment.Center;
g.DrawString(this._value.ToString("F2"), this.Font,Brushes.Black, valueBound, format);
format.Dispose();
}//end if Show Value
}//end in Length
}
#endregion

Method #2: FillCylinder

This method fills the cylinder given a handle to its graphics object.  It would be quite simple to rework this for other cylinder types.  It is found in the class, DrawingUtils.

Conclusions

It doesn't take too much code to wake up the view of a Windows Forms application and hopefully this will get you started along the right path.

Acknowledgements

Thanks to Jirapong Nanta here at Mycos for implementing the control in under 10 minutes and listening to my crazy ideas all the time.