[SDL] correct way of map scrolling

[Hasan Zorlu]

Hello !

i'm writing a little game with c# sdlDotNet, and i made my own map
scrolling. but i don't known its right way or not.
i create large map (5000x5000), actually i don't create 5000px surface
(you'll see below)

here is the code:

Game Class
----------------------------
public const int ScreenW = 1024;
//Screen Width
public const int ScreenH = 768;
    //Screen Height

public static int parseX = 0;
    //mapX in large map
public static int parseY = 0;
    //mapY in large map
public const short scrollSpeed = 10;
//map scrolling speed
public static char scrollWayX = 'N';
//scrolling where x? N = nowhere
public static char scrollWayY = 'N';
//scrolling where y? N = nowhere



Draw Method
-----------------------------------
Map.ParseMap(parseX, parseY);
//draw map objects (see above)
Video.Screen.Update();
//update screen


MouseMotion Method
-----------------------------------------
public void Motion ( MouseMotionEventArgs e ) {

   if (e.X > Game.ScreenW - 20) {
//mouse scroll right
       Game.parseX += Game.scrollSpeed;
//increase showmap X
       Game.scrollWayX = 'R';
     //set our way to R (Right)
   }
   else if (e.X < 10) {
         //mouse scroll left
       Game.parseX -= Game.scrollSpeed;
//decrease showmap X
       Game.scrollWayX = 'L';
//set our wat to L (Left)
   }
   else Game.scrollWayX = 'N';
//stop x scrolling



   if (e.Y > Game.ScreenH - 20) {
//mouse scroll down
       Game.parseY += Game.scrollSpeed;                           //increase
showmap Y
       Game.scrollWayY = 'D';
//set our way to D (Down)
   }
   else if (e.Y < 10) {
      //mouse scroll up
       Game.parseY -= Game.scrollSpeed;                           //decrease
showmap Y
       Game.scrollWayY = 'U';
//set our way to U (Up)
   }
   else Game.scrollWayY = 'N';
//stop y scrolling
}



Map File
-----------------------------------
#split ,  each line
#1. argument:       C is "Content Block" not used
#2. argument:       Sprite file name (1.png, 2.png, 3.png, 4.png)
#3. argument:       Sprite's X position in our map
#4. argument:       Sprite's Y position in our map

C,1,899,1200
C,2,949,1205
C,3,998,1190
C,4,2350,4500


Map Class - ParseMap Method
------------------------------------------------
//contents (SpriteConnection) variable in this method, loaded map contents
(see above)

public void ParseMap(int x, int y) {
                //parse current view map sprites

            int stopX = x + Game.ScreenW;
            //check end sprite's x
            int stopY = y + Game.ScreenH;
            //check end sprite's y

            int startX = x - Game.ScreenW;
                //check start sprite's x
            int startY = y - Game.ScreenH;
                //check start sprite's y


            for (int i = 0; i < contents.Count; i++) {
                //check for all map contents ("C" prefix lines in map file)
                bool parse = false;
                    //set parse or not option of each sprite

                if (contents[i].X >= 0 && contents[i].X <= stopX) {
         //if each sprite's x positions in our blocks
                    if (contents[i].Y >= 0 && contents[i].Y <= stopY) {
       //if each sprite's y positions in our blocks
                        parse = true;
                    //sprite is in our blocks, we can draw it
                    }
                }

                if (Game.scrollWayX == 'L') {
            //if mouse left scrolling
                    contents[i].X += Game.scrollSpeed;
          //mouse going left, sprite must go right
                }
                else if (Game.scrollWayX == 'R') {
             //if mouse right scrolling
                    contents[i].X -= Game.scrollSpeed;
           //mouse going right, sprite must go left
                }

                if (Game.scrollWayY == 'U') {
            //if mouse up scrolling
                    contents[i].Y += Game.scrollSpeed;
          //mouse going up, sprite must go down
                }
                else if (Game.scrollWayY == 'D') {
             //if mouse down scrolling
                    contents[i].Y -= Game.scrollSpeed;
           //mouse going down, sprite must go up
                }

                if (parse == true) {
                    //if we can draw this sprite
                    Video.Screen.Blit(contents[i],
contents[i].Rectangle);      //so draw it
                }
            }
}


basicly
- i set x and y of sprites (in map file),
- when mouse scrolling, check if any sprites in our 1024 x 768 block
(parse=true) blit sprite, if not in our block not draw (parse = false)

its working fine yet, but i scare about future if hundreds of sprite on our
map

Question is:
am i go wrong way or what?

What do you think about that?

thank you.

Hasan ZORLU
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