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
Solution 1:
For a "cleaner solution" and in order to keep using the base Panel, you could simply use Reflection to implement the double buffering, by adding this code to the form that holds the panels in which you want to draw in
typeof(Panel).InvokeMember("DoubleBuffered",
BindingFlags.SetProperty | BindingFlags.Instance | BindingFlags.NonPublic,
null, DrawingPanel, new object[] { true });
Where "DrawingPanel" is the name of the panel that you want to do the double buffering.
I know quite a lot of time has passed since the question was asked, but this might help somebody in the future.
Solution 2:
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!
Solution 3:
Copy and paste this into your project
protected override CreateParams CreateParams
{
get
{
CreateParams handleParam = base.CreateParams;
handleParam.ExStyle |= 0x02000000; // WS_EX_COMPOSITED
return handleParam;
}
}
This enables double-buffering for all controls from the form level down, otherwise double buffering needs to be individually enabled for each one... you may want to fine tune double bufferring after this because blanketed double buffering may give unwanted side effects.
Solution 4:
I have had the same problem. I was never able to 100% rid myself of the flicker (see point 2), but I used this
protected override void OnPaint(PaintEventArgs e) {}
as well as
this.DoubleBuffered = true;
The main issue for flickering is making sure you
- paint things it the right order!
- make sure your draw function is < about 1/60th of a second
winforms invokes the OnPaint method each time the form needs to be redrawn. There are many ways it can be devalidated, including moving a mouse cursor over the form can sometimes invoke a redraw event.
And important note about OnPaint, is you don't start from scratch each time, you instead start from where you were, if you flood fill the background color, you are likely going to get flickering.
Finally your gfx object. Inside OnPaint you will need to recreate the graphics object, but ONLY if the screen size has changed. recreating the object is very expensive, and it needs to be disposed before it is recreated (garbage collection doesn't 100% handle it correctly or so says documentation). I created a class variable
protected Graphics gfx = null;
and then used it locally in OnPaint like so, but this was because I needed to use the gfx object in other locations in my class. Otherwise DO NOT DO THIS. If you are only painting in OnPaint, then please use e.Graphics!!
// clean up old graphics object
gfx.Dispose();
// recreate graphics object (dont use e.Graphics, because we need to use it
// in other functions)
gfx = this.CreateGraphics();
Hope this helps.