147 lines
3.5 KiB
C
147 lines
3.5 KiB
C
/********************************
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Parallax sidescrolling starfield
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Jason Bou-Samra [ParagonSoft]
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28/03/2024
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to compile:
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cc -o stars stars.c -lSDL2
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********************************/
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#include <stdio.h>
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#include <stdlib.h>
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#include <SDL2/SDL.h>
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#include <stdbool.h>
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int initSDL (void);
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int shutdownSDL (void);
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bool quit = false; /* quit flag */
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SDL_Window *window = NULL;
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SDL_Renderer *sr;
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SDL_Event event;
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/* window paramaters */
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#define WIDTH 640 /* pixels */
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#define HEIGHT 512 /* pixels */
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#define TITLE "Starfield" /* window title */
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int StarAmount = 256;
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int xres = 640;
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int yres = 512;
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struct StarField { /* star structure */
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int x;
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int y;
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int speed;
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};
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int main(int argc, char **argv) /* allow StarAmount as paramater */
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{
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const char* filename = argv[1]; /* parse command line arguments */
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if (argc != 2){ /* display usage if less than 2 arguments passed */
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printf("Usage: stars [<quantity>|OPTION]\n\
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stars --help for help\n");
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return 1;
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} // display usage, then exit
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if(!strcmp(filename, "--about")) {
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printf("Paralax sidescrolling starfield\n\
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Jason Bou-Samra 28/03/2024.\n\n"); return 0;
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} /* display about, then exit */
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if(!strcmp (filename, "--help")) {
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printf("Usage: stars [<quantity>]\n\n\
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OPTIONS\n\
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--about displays about message\n\
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--help displays this help message\n"); return 0;
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}
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StarAmount = atoi(argv[1]);
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if (StarAmount == 0) {
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printf("invalid options\n\
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stars --help for help\n"); return 0;}
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initSDL ();
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struct StarField stars[StarAmount]; /* array of StarField structs, named stars */
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for (int x = 1; x < StarAmount; x++) /* setup initial values */
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{
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stars[x].x = rand() % (xres );
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stars[x].y = rand() % (yres );
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stars[x].speed = rand() % (5+1);
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}
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while (quit == false) { /* poll for quit event */
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while (SDL_PollEvent (&event))
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{
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if (event.type == SDL_QUIT || event.type == SDL_WINDOWEVENT_CLOSE)
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{
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quit = true;
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}
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}
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if (quit)
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{
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break; /* breakout of loop if quit is true */
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}
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SDL_SetRenderDrawColor(sr, 0x00, 0x00, 0x00, 0xFF); /* set background colour for window */
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SDL_RenderClear(sr); /* clear window */
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for (int x = 1; x < StarAmount; x++)
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{
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stars[x].x = stars[x].x + stars[x].speed;
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if (stars[x].x > xres)
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{
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stars[x].x = 0;
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stars[x].y = rand() % (yres );
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}
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SDL_SetRenderDrawColor(sr, 51*stars[x].speed, 51*stars[x].speed, 51*stars[x].speed, 0xFF); /* star color (R, G, B, A) */
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SDL_RenderDrawPoint(sr, stars[x].x, stars[x].y); /* plot star */
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}
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SDL_RenderPresent (sr);
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} // keep going until quit event
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shutdownSDL (); /* bye */
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return 0;
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}
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/* initialise SDL */
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int initSDL ()
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{
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SDL_Init (SDL_INIT_EVERYTHING);
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/* new window */
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window = SDL_CreateWindow (TITLE, /* title */
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SDL_WINDOWPOS_UNDEFINED, /* x pos */
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SDL_WINDOWPOS_UNDEFINED, /* w pos */
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WIDTH, /* width */
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HEIGHT, /* height */
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0); /* Additional flag(s) */
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/* deal with error */
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if (window == NULL)
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{
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fprintf (stderr, "SDL window failed to initialise: %s\n",
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SDL_GetError ());
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return 1;
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}
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/* creater renderer */
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sr = SDL_CreateRenderer (window, 0, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC);
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}
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/* shutdown routine */
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int shutdownSDL ()
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{
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SDL_DestroyWindow (window); /* free memory */
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SDL_Quit (); /* shutdown entire sdl sub-systems */
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return 0;
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}
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/* message */
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char message[] = { "Yes, Jesus loves you!" };
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