Help Repainting a Line
- by serhio
I am doing a custom control (inherited from VisualBasic.PowerPacks.LineShape), that should be painted like as standard one, but also having a Icon displayed near it.
So, I just overrided OnPaint like this:
protected override void OnPaint(System.Windows.Forms.PaintEventArgs e)
{
e.Graphics.DrawIcon(myIcon, StartPoint.X, StartPoint.Y);
base.OnPaint(e);
}
Now, everything is OK, but when my control moves, the icon still remains drawn on the ancient place.
Is there a way to paint it properly?
The sample code for tests
using Microsoft.VisualBasic.PowerPacks;
using System.Windows.Forms;
using System.Drawing;
namespace LineShapeTest
{
///
/// Test Form
///
public class Form1 : Form
{
IconLineShape myLine = new IconLineShape();
ShapeContainer shapeContainer1 = new ShapeContainer();
Panel panel1 = new Panel();
public Form1()
{
this.panel1.Dock = DockStyle.Fill;
// load your back image here
this.panel1.BackgroundImage =
global::WindowsApplication22.Properties.Resources._13820t;
this.panel1.Controls.Add(shapeContainer1);
this.myLine.StartPoint = new Point(20, 30);
this.myLine.EndPoint = new Point(80, 120);
this.myLine.Parent = this.shapeContainer1;
MouseEventHandler panelMouseMove =
new MouseEventHandler(this.panel1_MouseMove);
this.panel1.MouseMove += panelMouseMove;
this.shapeContainer1.MouseMove += panelMouseMove;
this.Controls.Add(panel1);
}
private void panel1_MouseMove(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
myLine.StartPoint = e.Location;
}
}
}
///
/// Test LineShape
///
public class IconLineShape : LineShape
{
Icon myIcon = SystemIcons.Exclamation;
protected override void OnPaint(System.Windows.Forms.PaintEventArgs e)
{
e.Graphics.DrawIcon(myIcon, StartPoint.X, StartPoint.Y);
base.OnPaint(e);
}
}
}
Nota Bene, for the lineShape:
Parent = ShapeContainer
Parent.Parent = Panel
Update 1 TRACES
In this variant of OnPaint, we have traces:
protected override void OnPaint(System.Windows.Forms.PaintEventArgs e)
{
Graphics g = Parent.Parent.CreateGraphics();
g.DrawIcon(myIcon, StartPoint.X, StartPoint.Y);
base.OnPaint(e);
}
Update 2 BLINKS
In this variant of OnPaint, we have a blinking image:
protected override void OnPaint(System.Windows.Forms.PaintEventArgs e)
{
Parent.Parent.Invalidate(this.Region, true);
Graphics g = Parent.Parent.CreateGraphics();
g.DrawIcon(myIcon, StartPoint.X, StartPoint.Y);
base.OnPaint(e);
}
Update 3: External Invalidation
This variant works well, but... from exterior of IconLineShape class:
private void panel1_MouseMove(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
Region r = myLine.Region;
myLine.StartPoint = e.Location;
panel1.Invalidate(r);
}
}
///
/// Test LineShape
///
public class IconLineShape : LineShape
{
Icon myIcon = SystemIcons.Exclamation;
Graphics parentGraphics;
protected override void OnPaint(System.Windows.Forms.PaintEventArgs e)
{
parentGraphics.DrawIcon(myIcon, StartPoint.X, StartPoint.Y);
base.OnPaint(e);
}
protected override void OnParentChanged(System.EventArgs e)
{
// Parent is a ShapeContainer
// Parent.Parent is a Panel
parentGraphics = Parent.Parent.CreateGraphics();
base.OnParentChanged(e);
}
}
Even this resolves the problem of the test example, I need this control to be done inside the control, because I can't force the external "clients" of this control do not forget to save the old region and invalidate the parent each time changing a location...
