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 != 0) 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 != 0 && (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 != 0)
{
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) ? 0 : SDL_abs(x); snake->x = (size) ? ((snake->x / SDL_abs(size)) * SDL_abs(size)) : 0; snake->y = (SDL_abs(y) > (world)->h) ? 0 : SDL_abs(y); snake->y = (size) ? ((snake->y / SDL_abs(size)) * SDL_abs(size)) : 0; snake->size = (size) ? SDL_abs(size) : 0; snake->color.r = snake->color.g = snake->color.b = snake->color.a = 0; snake->speed = 0; snake->length = 1; snake->direction = SNAKE_UP; snake->body = 0;
#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 (0)
#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 != 0) ? snake->body : 0; snake->body = (body); ++snake->length; } while (0)
#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 == 0) return 0;
if ((snake = (Snake *)SDL_malloc(sizeof(Snake))) == 0) return 0;
INIT_SNAKE(world, size, x, y);
SNK_GrowSnake(snake);
return snake;
}
void SNK_DestroySnake(Snake *snake)
{
struct Body *body;
if (snake != 0)
{
if ((body = snake->body)) REMOVE_BODY(body);
SDL_free(snake);
snake = 0;
}
}
void SNK_MoveSnake(Snake *snake)
{
struct Body *body;
if (snake != 0)
{
MOVE_SNAKE(snake);
for (body = snake->body; body; body = body->next)
{
MOVE_SNAKE(body);
body->direction = (body->next != 0) ? body->next->direction : snake->direction;
}
}
}
void SNK_DrawSnake(Snake *snake)
{
SDL_Rect rect;
struct Body *body;
if (snake != 0)
{
rect.x = snake->x;
rect.y = snake->y;
rect.w = rect.h = snake->size;
if (((snake->world != 0) ? (snake->world->render != 0) : 0))
{
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 != 0)
{
if ((body = (struct Body *)SDL_malloc(sizeof(struct Body))) == 0) return;
if (snake->body == 0)
{
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 != 0)
{
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) != 0)
return 1;
}
}
return 0;
}
int SNK_GetSnakeStatus(Snake *snake)
{
SDL_Rect headrect;
if (((snake != 0) ? (snake->world != 0) : 0))
{
headrect.w = (snake->x > 0 && snake->x < snake->world->w);
headrect.h = (snake->y > 0 && 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) != 0)
return SNAKE_DIED;
return SNAKE_MOVABLE;
}
else
{
switch (snake->direction)
{
case SNAKE_UP:
headrect.x = (snake->y > 0);
break;
case SNAKE_DOWN:
headrect.x = ((snake->y + snake->size) < snake->world->h);
break;
case SNAKE_LEFT:
headrect.x = (snake->x > 0);
break;
case SNAKE_RIGHT:
headrect.x = ((snake->x + snake->size) < snake->world->w);
break;
}
return ((headrect.x != 0) ? SNAKE_MOVABLE : 0);
}
}
return 0;
}
void SNK_SetSnakeSpeed(Snake *snake, int speed)
{
if (snake != 0) snake->speed = SDL_abs(speed);
}
void SNK_SetSnakeDirection(Snake *snake, int direction)
{
if (snake != 0 && (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 != 0)
{
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。
时间： 2024-08-06 15:35:49