[C入门 - 游戏编程系列] 贪吃蛇篇(六) - 蛇实现

时间:2023-03-09 04:14:59
[C入门 - 游戏编程系列]  贪吃蛇篇(六) - 蛇实现

  这一篇是关于设置蛇的属性的,接上一篇(五)。

设置蛇的速度,很简单,只要不是负数就行了。

void SNK_SetSnakeSpeed(Snake *snake, int speed)
{
if (snake != ) snake->speed = SDL_abs(speed);
}

设置蛇的方向有些复杂,玩过贪吃蛇的都知道,蛇向前移动时,它无法向后转弯;向左移动时,它无法向右转弯。所以,我也要做些这样的判断。

void SNK_SetSnakeDirection(Snake *snake, int direction)
{
if (snake != && (direction & (SNAKE_UP | SNAKE_DOWN | SNAKE_LEFT | SNAKE_RIGHT)))
{
if (snake->direction & (SNAKE_UP | SNAKE_DOWN))
{
if (direction & (SNAKE_LEFT | SNAKE_RIGHT))
snake->direction = direction;
}
else
{
if (direction & (SNAKE_UP | SNAKE_DOWN))
snake->direction = direction;
}
}
}

这样就能保证方向是对的,而且具有正确的转弯行为。

最后设置蛇的颜色,这个就没什么好说的了。

void SNK_SetSnakeColor(Snake *snake, Uint8 r, Uint8 g, Uint8 b, Uint8 a)
{
if (snake != )
{
snake->color.r = r;
snake->color.g = g;
snake->color.b = b;
snake->color.a = a;
}
}

到此,蛇的实现代码就写完了。整个游戏最核心的部分也就这些了,接下来就是弄个美观的界面了。

以下是snk-snake.c文件的完整源码:

#include "snk-snake.h"

#define INIT_SNAKE(world, size, x, y)                                       \
snake->world = (world); \
snake->x = (SDL_abs(x) > (world)->w) ? : SDL_abs(x); \
snake->x = (size) ? ((snake->x / SDL_abs(size)) * SDL_abs(size)) : ; \
snake->y = (SDL_abs(y) > (world)->h) ? : SDL_abs(y); \
snake->y = (size) ? ((snake->y / SDL_abs(size)) * SDL_abs(size)) : ; \
snake->size = (size) ? SDL_abs(size) : ; \
snake->color.r = snake->color.g = snake->color.b = snake->color.a = ; \
snake->speed = ; \
snake->length = ; \
snake->direction = SNAKE_UP; \
snake->body = ; #define MOVE_SNAKE(body) do { \
switch ((body)->direction) \
{ \
case SNAKE_UP: (body)->y -= snake->size; break; \
case SNAKE_DOWN: (body)->y += snake->size; break; \
case SNAKE_LEFT: (body)->x -= snake->size; break; \
case SNAKE_RIGHT:(body)->x += snake->size; break; \
} \
} while () #define APPEND_BODY(last, body) do { \
if ((last)->direction & (SNAKE_UP | SNAKE_DOWN)) { \
(body)->x = (last)->x; \
if ((last)->direction & SNAKE_UP) \
(body)->y = (last)->y + snake->size; \
else \
(body)->y = (last)->y - snake->size; \
} else { \
if ((last)->direction & SNAKE_LEFT) \
(body)->x = (last)->x + snake->size; \
else \
(body)->x = (last)->x - snake->size; \
(body)->y = (last)->y; \
} \
(body)->direction = (last)->direction; \
(body)->next = (snake->body != ) ? snake->body : ; \
snake->body = (body); \
++snake->length; \
} while () #define REMOVE_BODY(body) do { \
snake->body = (body)->next; \
SDL_free(body); \
(body) = snake->body; \
} while (body) Snake * SNK_CreateSnake(World *world, int size, int x, int y)
{
Snake *snake; if (world == ) return ; if ((snake = (Snake *)SDL_malloc(sizeof(Snake))) == ) return ; INIT_SNAKE(world, size, x, y);
SNK_GrowSnake(snake); return snake;
} void SNK_DestroySnake(Snake *snake)
{
struct Body *body; if (snake != )
{
if ((body = snake->body)) REMOVE_BODY(body); SDL_free(snake);
snake = ;
}
} void SNK_MoveSnake(Snake *snake)
{
struct Body *body; if (snake != )
{
MOVE_SNAKE(snake); for (body = snake->body; body; body = body->next)
{
MOVE_SNAKE(body);
body->direction = (body->next != ) ? body->next->direction : snake->direction;
}
}
} void SNK_DrawSnake(Snake *snake)
{
SDL_Rect rect;
struct Body *body; if (snake != )
{
rect.x = snake->x;
rect.y = snake->y;
rect.w = rect.h = snake->size; if (((snake->world != ) ? (snake->world->render != ) : ))
{
SDL_SetRenderDrawColor(snake->world->render,
snake->color.r, snake->color.g,
snake->color.b, snake->color.a);
SDL_RenderDrawRect(snake->world->render, &rect); for (body = snake->body; body; body = body->next)
{
rect.x = body->x;
rect.y = body->y;
SDL_RenderDrawRect(snake->world->render, &rect);
}
}
}
} void SNK_GrowSnake(Snake *snake)
{
struct Body *body; if (snake != )
{
if ((body = (struct Body *)SDL_malloc(sizeof(struct Body))) == ) return; if (snake->body == )
{
APPEND_BODY(snake, body);
}
else
{
APPEND_BODY(snake->body, body);
}
}
} int SNK_HasIntersection(Snake *snake, SDL_Rect rect)
{
SDL_Rect bodyrect;
struct Body *body; if (snake != )
{
bodyrect.w = bodyrect.h = snake->size; for (body = snake->body; body; body = body->next)
{
bodyrect.x = body->x;
bodyrect.y = body->y; if (SDL_HasIntersection(&bodyrect, &rect) != )
return ;
}
} return ;
} int SNK_GetSnakeStatus(Snake *snake)
{
SDL_Rect headrect; if (((snake != ) ? (snake->world != ) : ))
{
headrect.w = (snake->x > && snake->x < snake->world->w);
headrect.h = (snake->y > && snake->y < snake->world->h); if (headrect.w && headrect.h)
{
headrect.x = snake->x;
headrect.y = snake->y;
headrect.w = headrect.h = snake->size; if (SNK_HasIntersection(snake, headrect) != )
return SNAKE_DIED; return SNAKE_MOVABLE;
}
else
{
switch (snake->direction)
{
case SNAKE_UP:
headrect.x = (snake->y > );
break;
case SNAKE_DOWN:
headrect.x = ((snake->y + snake->size) < snake->world->h);
break;
case SNAKE_LEFT:
headrect.x = (snake->x > );
break;
case SNAKE_RIGHT:
headrect.x = ((snake->x + snake->size) < snake->world->w);
break;
} return ((headrect.x != ) ? SNAKE_MOVABLE : );
}
} return ;
} void SNK_SetSnakeSpeed(Snake *snake, int speed)
{
if (snake != ) snake->speed = SDL_abs(speed);
} void SNK_SetSnakeDirection(Snake *snake, int direction)
{
if (snake != && (direction & (SNAKE_UP | SNAKE_DOWN | SNAKE_LEFT | SNAKE_RIGHT)))
{
if (snake->direction & (SNAKE_UP | SNAKE_DOWN))
{
if (direction & (SNAKE_LEFT | SNAKE_RIGHT))
snake->direction = direction;
}
else
{
if (direction & (SNAKE_UP | SNAKE_DOWN))
snake->direction = direction;
}
}
} void SNK_SetSnakeColor(Snake *snake, Uint8 r, Uint8 g, Uint8 b, Uint8 a)
{
if (snake != )
{
snake->color.r = r;
snake->color.g = g;
snake->color.b = b;
snake->color.a = a;
}
}

宏INIT_SNAKE中snake->x和snake->y重复了两次,主要是为了将蛇的位置和蛇的大小对齐。

APPEND_BODY用于追加链表节点,并设置snake->body永远指向蛇尾,提高追加节点的效率。