Drawing an image on the control panel gives artifacts when resizing

Question

I'm currently trying to do what I thought would be a simple task:

Draw the image on the full Panel control area in Windows Forms. (Please ignore for now that I can use the BackgroundImage property)

The image for drawing is as follows:

those. yellow box with a 1-pixel blue border around.

To draw, I use the Paint event of the Panel control:

 private void panel1_Paint(object sender, PaintEventArgs e) { e.Graphics.DrawImage(Resources.MyImage, panel1.ClientRectangle); } 

This looks great when the form is initially displayed:

When resizing the form (and the docked panel, too), it either cuts the edges while reducing the size ...

... or he draws artifacts at magnification:

I am pretty sure that something pretty simple and straightforward is going on, but I really can't understand the reason.

Since I ignore ClipRectangle and always draw everything, I thought the image would scale all the time.

My questions:

• What is the reason for artifacts? (I love to understand that!)
• What do I need to do to get rid of artifacts? (besides calling Invalidate every time you resize)

Update, SOLUTION:

Thanks to Ryan's answer , I was able to find an acceptable solution. Basically, I got the class from Panel , made an override of OnPaintBackground and did not call the base method. Finally, I added the following code to the constructor of my derived panel:

 base.DoubleBuffered = true; SetStyle(ControlStyles.AllPaintingInWmPaint, true); SetStyle(ControlStyles.ResizeRedraw, true); SetStyle(ControlStyles.UserPaint, true); SetStyle(ControlStyles.OptimizedDoubleBuffer, true); UpdateStyles(); 

Answer 1

The reason for the artifacts is that the entire surface does not redraw when resizing the form; only necessary parts. The most optimal solution is what you do not want to do, calling Invalidate every time you resize. However, if this is actually your situation, just use a PictureBox . If this is not the case, you can instead replace OnPaint in your form and use this.SetStyle(ControlStyles.ResizeRedraw, true) to do this automatically.