Visible redraw while scrolling with large background images

Some more links:

http://www.developerfusion.co.uk/show/4668/
http://www.dotnet247.com/247reference/msgs/26/133167.aspx
http://winfx.msdn.microsoft.com/library/default.asp?url=/library/en-us/dv_fxmclignrl/html/91083d3a-653f-4f15-a467-0f37b2aa39d6.asp

Hi!

I'm not sure weather this will show better performance but it's worth trying.
You can load the background image into picturebox and display a portion of it on the form in the Paint event.

//-------------------------------------------------
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;

namespace WindowsApplication4
{
      /// <summary>
      /// Summary description for Form1.
      /// </summary>
      public class Form1 : System.Windows.Forms.Form
      {
            private System.Windows.Forms.PictureBox Pic1;
            private System.Windows.Forms.VScrollBar vScrollBar1;
            private System.Windows.Forms.HScrollBar hScrollBar1;
            /// <summary>
            /// Required designer variable.
            /// </summary>
            private System.ComponentModel.Container components = null;

            public Form1()
            {
                  //
                  // Required for Windows Form Designer support
                  //
                  InitializeComponent();

                  //
                  // TODO: Add any constructor code after InitializeComponent call
                  //
            }

            /// <summary>
            /// Clean up any resources being used.
            /// </summary>
            protected override void Dispose( bool disposing )
            {
                  if( disposing )
                  {
                        if (components != null)
                        {
                              components.Dispose();
                        }
                  }
                  base.Dispose( disposing );
            }

            #region Windows Form Designer generated code
            /// <summary>
            /// Required method for Designer support - do not modify
            /// the contents of this method with the code editor.
            /// </summary>
            private void InitializeComponent()
            {
                  System.Resources.ResourceManager resources = new System.Resources.ResourceManager(typeof(Form1));
                  this.Pic1 = new System.Windows.Forms.PictureBox();
                  this.vScrollBar1 = new System.Windows.Forms.VScrollBar();
                  this.hScrollBar1 = new System.Windows.Forms.HScrollBar();
                  this.SuspendLayout();
                  //
                  // Pic1
                  //
                  this.Pic1.Image = ((System.Drawing.Bitmap)(resources.GetObject("Pic1.Image")));
                  this.Pic1.Location = new System.Drawing.Point(248, 104);
                  this.Pic1.Name = "Pic1";
                  this.Pic1.Size = new System.Drawing.Size(208, 168);
                  this.Pic1.TabIndex = 0;
                  this.Pic1.TabStop = false;
                  this.Pic1.Visible = false;
                  //
                  // vScrollBar1
                  //
                  this.vScrollBar1.Location = new System.Drawing.Point(480, 0);
                  this.vScrollBar1.Name = "vScrollBar1";
                  this.vScrollBar1.Size = new System.Drawing.Size(16, 304);
                  this.vScrollBar1.TabIndex = 1;
                  this.vScrollBar1.Scroll += new System.Windows.Forms.ScrollEventHandler(this.vScrollBar1_Scroll);
                  //
                  // hScrollBar1
                  //
                  this.hScrollBar1.Location = new System.Drawing.Point(0, 304);
                  this.hScrollBar1.Name = "hScrollBar1";
                  this.hScrollBar1.Size = new System.Drawing.Size(480, 16);
                  this.hScrollBar1.TabIndex = 2;
                  this.hScrollBar1.Scroll += new System.Windows.Forms.ScrollEventHandler(this.hScrollBar1_Scroll);
                  //
                  // Form1
                  //
                  this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
                  this.ClientSize = new System.Drawing.Size(498, 320);
                  this.Controls.AddRange(new System.Windows.Forms.Control[] {
                                                                                                              this.hScrollBar1,
                                                                                                              this.vScrollBar1,
                                                                                                              this.Pic1});
                  this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.FixedSingle;
                  this.Name = "Form1";
                  this.Text = "Form1";
                  this.Load += new System.EventHandler(this.Form1_Load);
                  this.Paint += new System.Windows.Forms.PaintEventHandler(this.Form1_Paint);
                  this.ResumeLayout(false);

            }
            #endregion

            /// <summary>
            /// The main entry point for the application.
            /// </summary>
            [STAThread]
            static void Main()
            {
                  Application.Run(new Form1());
            }

            private void Form1_Load(object sender, System.EventArgs e)
            {
                  if (Pic1.Image.Width >= this.Width)
                  {
                        hScrollBar1.Minimum = 0;
                        hScrollBar1.Maximum = Pic1.Image.Width - Pic1.Width;
                  }
                  else
                        hScrollBar1.Enabled = false;
                  
                  if (Pic1.Image.Height >= this.Height)
                  {
                        vScrollBar1.Minimum = 0;
                        vScrollBar1.Maximum = Pic1.Image.Height - Pic1.Height;
                  }
                  else
                        vScrollBar1.Enabled = false;

            }

            private void Form1_Paint(object sender, System.Windows.Forms.PaintEventArgs e)
            {
                  System.Drawing.Graphics background = this.CreateGraphics();
                  System.Drawing.Rectangle DestRect = new System.Drawing.Rectangle(0,0,this.Width,this.Height);
                  
                  background.DrawImage(Pic1.Image,DestRect,hScrollBar1.Value,vScrollBar1.Value,this.Width,this.Height, System.Drawing.GraphicsUnit.Pixel);
            }

            private void hScrollBar1_Scroll(object sender, System.Windows.Forms.ScrollEventArgs e)
            {
                  Form1_Paint(hScrollBar1,new System.Windows.Forms.PaintEventArgs(this.CreateGraphics(),new System.Drawing.Rectangle(0,0,this.Width,this.Height)));
            }

            private void vScrollBar1_Scroll(object sender, System.Windows.Forms.ScrollEventArgs e)
            {
                  Form1_Paint(hScrollBar1,new System.Windows.Forms.PaintEventArgs(this.CreateGraphics(),new System.Drawing.Rectangle(0,0,this.Width,this.Height)));
            }
      }
}
//----------------------------------------------------------------------------------------------

Load an image into Pic1 at design time and run it

Try using LockWindowUpdate

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/gdi/pantdraw_4i5h.asp
http://www.webtropy.com/articles/art9-1.asp?f=LockWindowUpdate
http://www.experts-exchange.com/Programming/Programming_Languages/C_Sharp/Q_21291030.html


cheers

dbrckovi - this is exactly what I mentioned trying in my question above, and it was about 10 times worse :)

I'll play around today with alternatives, and I'll try the double buffering, as well as the LockWindowUpdate. I'll report back as I try things, if you think of something else for me to try, just post it here.

Thanks for your help,
-Sandra

Ok LockWindowUpdate seems only to be for preventing the control from drawing, it doesn't help with anything in the OnPaint method.

I set up a bitmap buffer, and I drew the section of the image to the buffer, and this works great. I tried drawing the image in the OnPaint method but this flickers. So I set the BackgroundImage property to the buffer in the constructor and call Invalidate() once I'm done drawing to the buffer. The flicker is gone. But it lags so badly when scrolling (visible jerkiness and 100% cpu utilization) that it's even worse.

I think it's time for me to break out directx.

-Sandra

I am not sure, but maybe it will be possible to make it faster with C++. Unfortunately I cannot help you a lot in "how" to do it...

It may be faster in C++, but I may as well use directx, I have a feeling it may save me more headaches like this down the road.

Thanks for your help guys.

-Sandra

For anybody who might read this later, if you have flickering or lag when painting a window and you can't get rid of it in .NET you can use C++ and draw to an off screen buffer then Blt the buffer to the screen in response to WM_PAINT message.

The process is described here:

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dngdi/html/msdn_flicker.asp

Then you can create a managed C++ wrapper around your C++ window to bring it into C# or VB.NET.

Try this for a starting point:

http://www.thecodeproject.com/managedcpp/mfcandwindowsforms.asp

-Sandra