I'm trying to make a trackbar with a custom graphic for the slider thumb. I have started out with the following code:
namespace testapp
{
partial class MyTrackBar : System.Windows.Forms.TrackBar
{
public MyTrackBar()
{
InitializeComponent();
}
protected override void OnPaint(System.Windows.Forms.PaintEventArgs e)
{
// base.OnPaint(e);
e.Graphics.FillRectangle(System.Drawing.Brushes.DarkSalmon, ClientRectangle);
}
}
}
But it never calls OnPaint. Anyone else come across this? I have used this technique before to create an ownerdraw button but for some reason it doesn't work with TrackBar.
PS. Yes, I have seen question #625728 but the solution there was to completely re-implement the control from scratch. I just want to modify the existing control a little.
If you want to paint over the top of the trackbar you can capture the WM_PAINT message manually, this means you dont have to re-write all the painting code yourself and can simply paint it, like this:
using System.Drawing;
using System.Windows.Forms;
namespace TrackBarTest
{
public class CustomPaintTrackBar : TrackBar
{
public event PaintEventHandler PaintOver;
public CustomPaintTrackBar()
: base()
{
SetStyle(ControlStyles.AllPaintingInWmPaint, true);
}
protected override void WndProc(ref Message m)
{
base.WndProc(ref m);
// WM_PAINT
if (m.Msg == 0x0F)
{
using(Graphics lgGraphics = Graphics.FromHwndInternal(m.HWnd))
OnPaintOver(new PaintEventArgs(lgGraphics, this.ClientRectangle));
}
}
protected virtual void OnPaintOver(PaintEventArgs e)
{
if (PaintOver != null)
PaintOver(this, e);
// Paint over code here
}
}
}
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