Galgame引擎编写，图像层

BG类层，立绘层，字符层，ui层。目前还没有好的方法将这些层统一为一种概念，排序也没有考虑，Game逻辑部分管理BG, ACTOR层。
typedef enum {
    SF_BAD = -1,
    SF_HIDE,    // effect使用
    SF_PIC,    // bg, actor
    SF_POLY,    // 绘制多边形
    SF_SHEET    // 绘制字符，粒子类
}surfaceType_t;
bg及立绘层定义
struct drawSurf_t {
    int     sort;
    surfaceType_t    *surface;

    drawSurf_t() : sort(-1), surface(NULL) {}
};

struct srfPic_t {
    surfaceType_t    surfaceType;
    ALLEGRO_BITMAP    *image;
    float    sx, sy, sw, sh;     //size

    ALLEGRO_COLOR    color;
    float    dx, dy, dw, dh;
    float    cx, cy, angle;

    void Clear() {
        surfaceType = SF_BAD;
        image = NULL;
        sx = sy = sw = sh = 0.0f;
        color.a = 1;
        color.r = 1;
        color.g = 1;
        color.b = 1;
        dx = dy = dw = dh = 0;
        cx = cy = angle = 0;
    }
    srfPic_t() {
        Clear();
    }
};

struct sheetSize_t {
    float    sx, sy, sw, sh;
    float    dx, dy;
};

struct srfSheet_t {
    surfaceType_t    surfaceType;
    ALLEGRO_BITMAP    *image;
    ALLEGRO_COLOR    color;
    int     numSheets;
    sheetSize_t     *sheets;

    void Clear() {
    surfaceType = SF_BAD;
    image = NULL;
    color.a = 1;
    color.r = 1;
    color.g = 1;
    color.b = 1;
    numSheets = 0;
    sheets = NULL;
    }
    srfSheet_t() {
        Clear();
    }
};