BigBug BigBug - 2 months ago 13
C# Question

how to stop flickering C# winforms

I have a program that is essentially like a paint application. However, my program has some flickering issues. I have the following line in my code (which should get rid of flickering - but doesn't):

this.SetStyle(ControlStyles.AllPaintingInWmPaint
| ControlStyles.UserPaint | ControlStyles.DoubleBuffer, true);


my code(minus the super and sub classes for the shapes is as follows:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace Paint
{
public partial class Paint : Form
{
private Point startPoint;
private Point endPoint;
private Rectangle rect = new Rectangle();
private Int32 brushThickness = 0;
private Boolean drawSPaint = false;
private List<Shapes> listOfShapes = new List<Shapes>();
private Color currentColor;
private Color currentBoarderColor;
private Boolean IsShapeRectangle = false;
private Boolean IsShapeCircle = false;
private Boolean IsShapeLine = false;

public SPaint()
{

InitializeComponent();
this.SetStyle(ControlStyles.AllPaintingInWmPaint | ControlStyles.UserPaint | ControlStyles.DoubleBuffer, true);

currentColor = Color.Red;
currentBoarderColor = Color.DodgerBlue;
IsShapeRectangle = true;
}

private void panelArea_Paint(object sender, PaintEventArgs e)
{
Graphics g = panelArea.CreateGraphics();

if (drawSPaint == true)
{

Pen p = new Pen(Color.Blue);
p.DashStyle = System.Drawing.Drawing2D.DashStyle.Dash;

if (IsShapeRectangle == true)
{
g.DrawRectangle(p, rect);
}
else if (IsShapeCircle == true)
{
g.DrawEllipse(p, rect);
}
else if (IsShapeLine == true)
{
g.DrawLine(p, startPoint, endPoint);
}
}
foreach (Shapes shape in listOfShapes)
{

shape.Draw(g);

}
}

private void panelArea_MouseDown(object sender, MouseEventArgs e)
{

startPoint.X = e.X;
startPoint.Y = e.Y;

drawSPaint = true;
}

private void panelArea_MouseMove(object sender, MouseEventArgs e)
{


if (e.Button == System.Windows.Forms.MouseButtons.Left)
{

if (e.X > startPoint.X)
{
rect.X = startPoint.X;
rect.Width = e.X - startPoint.X;
}
else
{
rect.X = e.X;
rect.Width = startPoint.X - e.X;
}
if (e.Y > startPoint.Y)
{
rect.Y = startPoint.Y;
rect.Height = e.Y - startPoint.Y;
}
else
{
rect.Y = e.Y;
rect.Height = startPoint.Y - e.Y;
}


panelArea.Invalidate();

}

}

private void panelArea_MouseUp(object sender, MouseEventArgs e)
{

endPoint.X = e.X;
endPoint.Y = e.Y;

drawSPaint = false;

if (rect.Width > 0 && rect.Height > 0)
{
if (IsShapeRectangle == true)
{
listOfShapes.Add(new TheRectangles(rect, currentColor, currentBoarderColor, brushThickness));
}
else if (IsShapeCircle == true)
{
listOfShapes.Add(new TheCircles(rect, currentColor, currentBoarderColor, brushThickness));
}
else if (IsShapeLine == true)
{
listOfShapes.Add(new TheLines(startPoint, endPoint, currentColor, currentBoarderColor, brushThickness));
}

panelArea.Invalidate();
}
}


private void rectangleToolStripMenuItem_Click(object sender, EventArgs e)
{
IsShapeRectangle = true;
IsShapeCircle = false;
IsShapeLine = false;
}

private void ellipseToolStripMenuItem_Click(object sender, EventArgs e)
{
IsShapeRectangle = false;
IsShapeCircle = true;
IsShapeLine = false;
}

private void lineToolStripMenuItem_Click(object sender, EventArgs e)
{
IsShapeCircle = false;
IsShapeRectangle = false;
IsShapeLine = true;
}

private void ThicknessLevel0_Click(object sender, EventArgs e)
{
brushThickness = 0;
}

private void ThicknessLevel2_Click(object sender, EventArgs e)
{
brushThickness = 2;
}

private void ThicknessLevel4_Click(object sender, EventArgs e)
{
brushThickness = 4;
}

private void ThicknessLevel6_Click(object sender, EventArgs e)
{
brushThickness = 6;
}

private void ThicknessLevel8_Click(object sender, EventArgs e)
{
brushThickness = 8;
}

private void ThicknessLevel10_Click(object sender, EventArgs e)
{
brushThickness = 10;
}

private void ThicknessLevel12_Click(object sender, EventArgs e)
{
brushThickness = 12;
}

private void ThicknessLevel14_Click(object sender, EventArgs e)
{
brushThickness = 14;
}

private void FillColour_Click(object sender, EventArgs e)
{

ColorDialog fillColourDialog = new ColorDialog();
fillColourDialog.ShowDialog();
currentColor = fillColourDialog.Color;
panelArea.Invalidate();
}

private void button1_Click(object sender, EventArgs e)
{

ColorDialog fillColourDialog = new ColorDialog();
fillColourDialog.ShowDialog();
currentBoarderColor = fillColourDialog.Color;
panelArea.Invalidate();
}


}
}


How do i stop the flickering?

*UPDATE:*This code actually works great when i'm drawing directly on the form. However, when i try to draw on the panel, flickering becomes an issue

Answer

Finally solved the flickering. Since I was drawing on a panel instead of the form the line of code below will not solve the flickering:

this.SetStyle(
    ControlStyles.AllPaintingInWmPaint | 
    ControlStyles.UserPaint | 
    ControlStyles.DoubleBuffer, 
    true);

SetStyle must be of type 'YourProject.YourProject' (or derived from it) hence, you have to create a class as such (so that you can use MyPanel which will be derived from SPaint.SPaint and hence allowing you to use doublebuffering directly for the panel - rather than the form):

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using SPaint; 

namespace YourProject
{
    public class MyPanel : System.Windows.Forms.Panel
    {
        public MyPanel()
        {
            this.SetStyle(
                System.Windows.Forms.ControlStyles.UserPaint | 
                System.Windows.Forms.ControlStyles.AllPaintingInWmPaint | 
                System.Windows.Forms.ControlStyles.OptimizedDoubleBuffer, 
                true);
        }
    }
}

After you've done this(although you should really never edit the designer code unless you truly know what you're doing) you'll have to edit the Form.Designer.cs. Inside this file you will find code that looks like this:

this.panelArea = new YourProject.MyPanel();

The above line needs to be changed to:

this.panelArea = new MyPanel(); 

After I completed these steps, my paint program no longer flickers.

For anyone else having the same issue, the problem is finally solved.

Enjoy!

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