Thread: graphic updates not doing what i thought

another thing i noticed...if panel2 is what you want the changes to reflect, you're overriding the wrong method.

your override OnPaint looks like you're overriding the Form, not the panel2's paint. try hooking into the splitContainer.Panel2.Paint event.

hmmm, hope this explains it.

Code:

class MyForm {
  public MyForm() {
    this.Paint += PaintHandler;
  }

  protected override OnPaint(PaintEventArgs e) {
    // this 'overrides' the base class (Form) painting method.
    base.OnPaint(e);
    e.Graphics.Draw(1); // for simplicity, let's assume this is valid and outputs 1
  }

  private void PaintHandler(object sender, PaintEventArgs e) {
    // this listens to the paint
    e.Graphics.Draw(2); // outputs 2
  }
};

when the above class refreshes it will draw 1 and then 2.

there are 2 ways to draw on a control. the 1st is to override the Paint method (of which you should *not* comment out the base.OnPaint()). and the 2nd is to listen to the event, which you need to do if you are not a subclass.

ok - im getting more confused

if i add a paint handler to the panel2 properties it creates this

Code:

protected void splitContainer1_Panel2_Paint(object sender, PaintEventArgs e)
        {

        }

a. why cant i use the override to change it to my event handler( as i can do with OnPaint)

b. can i just put what i want it to paint in there - as in my 'backg' bitmap ?

i get what your saying about the creategraphics being recreated on every paint event and will look at where i should move that later(im guessing it need to go up in the form1() area to make sure it is globally visible ?).

everything works perfectly well in my original setup apart from the flickering, i have suspected it being the update method for a while now but couldnt see why.

a) you can't override it because Form is not a subclass of SplitContainer.Panel.
b) yes, as long as backg is scope-visible

ok - here is my main update method - this links to the previously posted Onpaint method.

Code:

 public void updatemap()
        {
            
            backg = new Bitmap(splitContainer1.Panel2.Width, splitContainer1.Panel2.Height);
            Graphics temp = Graphics.FromImage(backg);

           //... do all the graphics drawing etc here

            this.Invalidate(); // invalidate area
            this.Update(); // force a redraw
        }

note : backg is declared as a global.
going on what Bling said about on declaring the CreatGraphics() once (in the onpaint routine)- can anyone point out where i would implement this call in this method ?

every time you call updatemap() you'll just create another Bitmap and Graphics object. even though backg may be global, you're just replacing it with new object every time you call that method. create a bitmap object ONCE.

if you need it to dynamically resize, listen to the Resize event and properly create a new Bitmap/Graphics pair and Dispose() the old ones.

i have added the paint handler and this is working ( using my old code anyway so at least i know i have it set right as per your instructions)

Backg is now declared in the main form method.

in the update method i now create :-

Graphics temp = splitContainer1.Panel2.CreateGraphics();

and whatever needs doing in there ( however i have disabled the invalidate and update for the moment)

it works but i can see that i am still drawing directly to the panel2 and my paint handler asks for :-

e.Graphics.DrawImage(backg, 0, 0);

how do i set this so whatever i draw on 'Temp' goes to 'Backg'. as backg is global and temp is not and cannot be declared outside of form() as it does not exist before the initialisation ?

also backg is a bitmap and temp is a graphic.

or have i just totally got this messed up in my head - really sorry bling

i think it'd be worthwhile for you to google some tutorials on how to draw custom controls via C#/.NET.

ok - first off apologies to bling - i misunderstood/ misinterpreted what you were saying about the override on the handler and was not overriding the event for the panel2 paint event - this is now rectified.

it definately draws to panel2 in there now.

the backg bitmap is declared in the form() as is the graphic for temp. ( this is still not doing what i expect and i will look into it some more later.)

so apologies to anyone who looks at this and thinks - WHAT THE HELL !!!

sorry

just post the code

Code:

public Form1()
        {
            InitializeComponent();

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

            for (int x = 0; x < gridx; x++)  // set initial array to -1 ( for checking purposes)
                for (int y = 0; y < gridy; y++)
                    Map[x, y] = -1;


            splitContainer1.Panel2.Paint += painthandler;

            ImgList.ImageSize = new Size(32, 32);
            setup_tile_bar();
            do_pictureboxs();
            
           
            backg = new Bitmap(splitContainer1.Panel2.Width, splitContainer1.Panel2.Height);
            temp = splitContainer1.Panel2.CreateGraphics();
            //temp = Graphics.FromImage(backg);

            updatemap();

            foreach (var PictureBox in mypicturebox)
            {
                PictureBox.Click += new EventHandler(picClick); // setup eventhandlers for picture boxs
            }

        }

 public void painthandler(object sender, PaintEventArgs e)
        {
            e.Graphics.Clear(Color.Red);
            e.Graphics.DrawImage(backg, 0, 0);  <-- i believe this is the problem here
            
        }

 public void updatemap()
        {
            //draw the grid

            for (int i = 0; i < gridx + 1; i++)
                temp.DrawLine(new Pen(Color.White), new Point(i * 32, 0), new Point(i * 32, (splitContainer1.Panel2.Height)));
            for (int i = 0; i < gridy + 1; i++)
                temp.DrawLine(new Pen(Color.White), new Point(0, i * 32), new Point((splitContainer1.Panel2.Width), i * 32));

            // check map for values outside of current tileset and reset to picturebox 0
            if (ImgList.Images.Count != 0)
            {
                for (int x = 0; x < gridx; x++) // overlay tile map onto grid
                    for (int y = 0; y < gridy; y++)
                    {
                        if (Map[x, y] >= ImgList.Images.Count)
                            Map[x, y] = 0;  // clear the tile value if no tile exists to replace it
                    }
            }
            
            for (int x = 0; x < gridx; x++) // overlay tile map onto grid
            {
                for (int y = 0; y < gridy; y++)
                {
                    imageval = Map[x, y];

                    if (imageval >= 0 && ImgList.Images.Count > 0)
                        temp.DrawImage(ImgList.Images[imageval], x * 32, y * 32);
                }
            }

            if (dragging)
            {
                int tempstartx = rectstartx; // temp variables so as not to corrupt actual start and end co-ords!
                int tempstarty = rectstarty;
                int width = rectendx - rectstartx;
                int height = rectendy - rectstarty;

                if (rectstartx > rectendx)
                    width = rectstartx - rectendx;
                if (rectstarty > rectendy)
                    height = rectstarty - rectendy;

                if (rectstartx > rectendx) //swap start to end if end is less than start
                {
                    tempstartx = rectendx;
                }

                if (rectstarty > rectendy)
                {
                    tempstarty = rectendy;
                }
                temp.DrawRectangle(Pens.White, tempstartx, tempstarty, width, height);

            }

            this.Invalidate(); // invalidate area
            this.Update(); // force a redraw
        }

here are the relevant sections that deal with the drawing and updates.

hope this helps - it si definatley an issue where the rendered section is not being rendered back to panel2. but i cnat see where or why