We have discussed in the previous sections how to do simple animations with a pre-created image that contains sequences of bitmaps; a few simple classes and a thread are used to achieve the effects. Here, we show you the complete code which is ready to compile and execute. The program "jewels.cpp" shown below is the complete code you need. You can copy-and-paste it into a file named "jewels.cpp" and compile it by the command:

$g++ -o jewels jewels.cpp -lSDL -lSDL_image

To run it, you can simply execute

$./jewels

However, before you run the program, you have to create a subdirectory "images" and put the image files "jboard.jpg" and "jewels.png" in it.

/* jewels.cpp : Demonstration of Animation using SDL Compile: g++ -o jewels jewels.cpp -lSDL -lSDL_image Execute: ./jewels See http://www.webkinesia.com/games/sdl-animate.php @Author: Fore June */ #include <iostream> #include <stdlib.h> #include <math.h> #include <deque> #include <SDL/SDL.h> #include <SDL/SDL_thread.h> #include <SDL/SDL_image.h> using namespace std; #define Location Point #define JWIDTH 52 #define JHEIGHT 52 bool quit = false; class Point { public: short x; short y; Point () { x = y = 0; } Point ( short x0, short y0 ) { x = x0; y = y0; } }; Point point_1 ( -1, -1 ); class Jewel { public: short jType; //type of jewel Point dest; //position to display jewel }; //The Jewel Board class JBoard { public: Jewel jewels[8][8]; //jewels on the board Point jSource[7]; //source locations of various jewels SDL_Surface *image; //source image of all jewels SDL_Surface *imageMain; //source image of main board SDL_Surface *screen; //destination for displaying images short width; //size of jewel ( all the same ) short height; JBoard( SDL_Surface *scr ); //constructor bool init(); //initialize the board short x2Col ( short x ); //find col # corresponding to x short y2Row ( short y ); //find row # corresponding to y Location jewelLocation ( Point p ); //find ( col#, row# ) of Point p short neighbour ( Location m, Location n ); //determine if m, n are neighbours bool swapJewels ( Location a, Location b ); //swap two adjacent jewels }; //create the board JBoard::JBoard( SDL_Surface *scr ) { SDL_Rect source, dest; screen = scr; imageMain = IMG_Load ( "images/jboard.jpg" ); //source image of main board if ( imageMain == NULL ) { cout << "Unable to load image\n"; return; } image = IMG_Load ( "images/jewels.png" ); //source image of main board if ( image == NULL ) { cout << "Unable to load image\n"; return; } /* remember where to get the jewels totally there are 7 different kind of jewels */ short x, y, i, j, k; width = 48; //size of jewel height = 48; x = 3; //location of first jewel y = 3; for ( i = 0; i < 7; ++i ) { jSource[i] = Point ( x, y ); y += 104; //location of next jewel, same x, different y if ( i == 4 || i == 5 ) y -= 1; //make small adjustments in positions } /* remember where to put the jewels starting position is ( 20, 204 ) */ y = 20; //starting y position for ( i = 0; i < 8; ++i ) { x = 204; for ( j = 0; j < 8 ; ++j ) { jewels[i][j].dest = Point ( x, y ); x += 51; //next jewel } y += 51; //next row if (i == 2) y-=1; //make minor adjustment } } //JBoard() bool JBoard::init() { short k; SDL_Rect source, dest; source.x = 0; source.y = 0; source.w = imageMain->w; source.h = imageMain->h; dest.x = dest.y = 0; SDL_BlitSurface ( imageMain, &source, screen, &dest ); source.w = width; //all jewels have same size source.h = height; //now populate the board randomly with jewels srand ( ( unsigned )time ( NULL ) ); //random seed for ( short i = 0; i < 8; ++i ) { for ( short j = 0; j < 8; ++j ) { k = rand() % 7; jewels[i][j].jType = k; source.x = jSource[k].x; source.y = jSource[k].y; dest.x = jewels[i][j].dest.x; dest.y = jewels[i][j].dest.y; SDL_BlitSurface ( image, &source, screen, &dest ); } } if( SDL_Flip( screen ) == -1 ) return false; return true; } //find the column # corresponding to x position short JBoard::x2Col ( short x ) { if ( x < jewels[0][0].dest.x || x > ( jewels[0][7].dest.x + JWIDTH ) ) return -1; short i; for ( i = 1; i < 8; ++i ) //simple linear search if ( x < jewels[0][i].dest.x ) break; return i - 1; } //find the row # corresponding to y position short JBoard::y2Row ( short y ) { if ( y < jewels[0][0].dest.y || y > ( jewels[7][0].dest.y + JHEIGHT )) return -1; short i; for ( i = 1; i < 8; ++i ) //simple linear if ( y < jewels[i][0].dest.y ) break; return i - 1; } Location JBoard::jewelLocation ( Point p ) { short i, j; i = x2Col ( p.x ); if ( i < 0 ) return point_1; j = y2Row ( p.y ); if ( j < 0 ) return point_1; return Location ( i, j ); } short JBoard::neighbour ( Location m, Location n ) { if ( (m.y - n.y) == 0 ) { //same row if ( abs ( m.x - n.x ) == 1 ) //neighbouring cols return 1; } else if ( ( m.x - n.x ) == 0 ) { //same col if ( abs ( m.y - n.y ) == 1 ) //neighbouring rows return 0; } return -1; //non neighbours } /* Swap adjacent jewels. */ bool JBoard::swapJewels ( Location m, Location n ) { short adj_col = neighbour ( m, n ); //0 => adj. rows, 1 => adj. cols, -1 => non-neighbours if ( adj_col < 0 ) //m, n are not neighbours return false; SDL_Rect source_m, source_n, dest_m, dest_n, source0, source1, dest0, dest1; short i, j, k, update_w, update_h; if ( adj_col ) { k = m.x - n.x; update_w = JWIDTH * 2; update_h = JHEIGHT; } else { k = m.y - n.y; update_w = JWIDTH; update_h = JHEIGHT * 2; } //Ensure m is on left or top of n if ( k > 0 ) { Location temp = m; //swap m, n m = n; n = temp; } dest_n.w = dest_m.w = source_n.w = source_m.w = width; dest_n.h = dest_m.h = source_n.h = source_m.h = height; i = m.y; j = m.x; dest_m.x = jewels[i][j].dest.x; dest_m.y = jewels[i][j].dest.y; k = jewels[i][j].jType; source_m.y = jSource[k].y; source_m.x = jSource[k].x; i = n.y; j = n.x; dest_n.x = jewels[i][j].dest.x; dest_n.y = jewels[i][j].dest.y; k = jewels[i][j].jType; source_n.y = jSource[k].y; source_n.x = jSource[k].x; short d; //distance two jewels need to travel in swapping if ( adj_col ) d = jewels[n.y][n.x].dest.x - dest_m.x; else d = jewels[n.y][n.x].dest.y - dest_m.y; source0.x = dest0.x = dest_m.x - 2; //backgrounds source0.y = dest0.y = dest_m.y - 2; source1.x = dest1.x = dest_n.x - 2; source1.y = dest1.y = dest_n.y - 2; source0.w = source1.w = JWIDTH; source0.h = source1.h = JHEIGHT; for ( int r = 0; r < d; ++r ) { SDL_BlitSurface ( imageMain, &source0, screen, &dest0 ); //first jewel background SDL_BlitSurface ( imageMain, &source1, screen, &dest1 ); //second jewel background SDL_BlitSurface ( image, &source_m, screen, &dest_m ); //first jewel image SDL_BlitSurface ( image, &source_n, screen, &dest_n ); //second jewel image SDL_UpdateRect( screen, source0.x, source0.y, update_w, update_h ); //update affected region if ( adj_col ) { dest_m.x += 1; //first jewel goes right dest_n.x -= 1; //second jewel goes left } else { dest_m.y += 1; //first jewel goes down dest_n.y -= 1; //second jewel goes up } SDL_Delay ( 5 ); } //swap the states of the jewels k = jewels[m.y][m.x].jType; jewels[m.y][m.x].jType = jewels[n.y][n.x].jType; jewels[n.y][n.x].jType = k; } //swapJewels class JMouse { private: short x; short y; public: JBoard *jBoard; JMouse ( JBoard *jb ); void doJewel( Point p, short action ); //rotate or flash jewel }; JMouse::JMouse ( JBoard *jb ) { jBoard = jb; x = y = 0; } /* Rotate or flash the jewel located at p. If p is outside board, returns. action = 0 => flash, action = 1 => rotate */ void JMouse::doJewel ( Point p, short action ) { if ( action < 0 ) return; Location loc = jBoard->jewelLocation ( p ); if ( loc.x < 0 ) { cout << "outside board " << endl; return; } short i, j, k; i = loc.y; //i, j roles are reversed here j = loc.x; k = (jBoard->jewels[i][j]).jType; SDL_Rect source, dest; dest.w = source.w = jBoard->width; dest.h = source.h = jBoard->height; dest.x = jBoard->jewels[i][j].dest.x; dest.y = jBoard->jewels[i][j].dest.y; source.y = jBoard->jSource[k].y; //source points to row for rotation if ( action == 0 ) //point to next row which is for flashing source.y += JHEIGHT; source.x = jBoard->jSource[k].x; for ( int i = 0; i < 15; ++i ) { SDL_BlitSurface ( jBoard->imageMain, &dest, jBoard->screen, &dest ); //background SDL_BlitSurface ( jBoard->image, &source, jBoard->screen, &dest ); //image SDL_UpdateRect( jBoard->screen, dest.x, dest.y, JWIDTH, JHEIGHT ); SDL_Delay ( 30 ); source.x += JWIDTH; //next image } } deque<Point> mouse_down_queue; int mouse_thread ( void *jmouse ) { JMouse *jm = ( JMouse *) jmouse; short action = -1; //no action at beginning short nevent = 0; Point p; Location m, n; while ( !quit ) { if ( mouse_down_queue.size() > 0 ) { m = n; p = mouse_down_queue.front(); n = jm->jBoard->jewelLocation( p ); mouse_down_queue.pop_front(); action = rand() % 2; //randomly set for rotation (1) or flashing (0) ++nevent; } if ( nevent == 2 ) { if ( jm->jBoard->neighbour ( m, n ) >= 0 ) { jm->jBoard->swapJewels ( m, n ); //swap two jewels action = -1; nevent = 0; } else --nevent; } else jm->doJewel ( p, action ); //rotate or flash } return 0; } int main() { #ifndef ARM const int VWIDTH = 640; const int VHEIGHT = 480; #else const int VWIDTH = 320; const int VHEIGHT = 240; #endif SDL_Surface *screen; SDL_Event event; /* Fire up SDL. */ if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO ) < 0) { printf("Error initializing SDL: %s\n", SDL_GetError()); return 1; } atexit(SDL_Quit); /* Set a video mode. Force 16-bit hicolor. */ if ((screen = SDL_SetVideoMode(VWIDTH, VHEIGHT, 16, 0)) == NULL) { printf("Error setting a video, 16-bit video mode: %s\n", SDL_GetError()); return 1; } JBoard jb ( screen ); jb.init(); Location n ( 3, 4), m ( 4, 4 ); jb.swapJewels ( m, n ); n = Location ( 4, 3 ); m = Location ( 4, 4 ); jb.swapJewels ( m, n ); m = Location ( 4, 5 ); n = Location ( 5, 5 ); jb.swapJewels ( m, n ); m = Location ( 2, 4 ); n = Location ( 2, 5 ); jb.swapJewels ( m, n ); Point p; JMouse jm ( &jb ); SDL_Thread *mthread; mthread = SDL_CreateThread( mouse_thread, &jm ); while (SDL_WaitEvent(&event)) { switch (event.type) { case SDL_MOUSEBUTTONDOWN: p = Point ( event.button.x, event.button.y ); mouse_down_queue.push_back ( p ); break; case SDL_KEYUP: if (event.key.keysym.sym == SDLK_ESCAPE) { SDL_Quit(); quit = true; } break; } } SDL_WaitThread( mthread, NULL ); return 0; }