读书笔记《30天自制操作系统》day10

1. 显示到屏幕上的图形界面信息要分层，比如最顶层是鼠标，中间是应用程序，最低是桌面。

2. 移动鼠标和窗口应用可以看为是移动图层。

3. 屏幕显示的原理是向显存内写信息，显存的地址在0x000a0000这个已经在前面见过了。

/*一个图层结构体*/struct SHEET{    unsigned char* buf;/*图层内容地址*/    int bxsize,bysize;/*图层大小*/    int vx0,vy0;/*图层在屏幕上位置*/    int col_inv;/*色号（调色板）*/    int height;/*图层高度*/    int flag;/*设定信息*/};/*管理多个图层结构体*/#define MAX_SHEETS 256struct SHTCTL{    unsigned char *vram;/*VRAM地址*/    int xsize,ysize;/*屏幕宽高*/    int top;/*最上图层高度*/    struct SHEET * sheets[MAX_SHEETS];/*下面的图层信息混乱，所以按照高度进行排序*/    struct SHEET sheets0[MAX_SHEETS];/*保存所有图层信息*/};

4. 内存空间的分配应使用前面学过的知识，不使用static分配，初始化图层管理节点，一次性分配足够大的管理空间

#define SHEET_USE1struct SHTCTL *shtctl_init(struct MEMMAN *memman, unsigned char *vram, int xsize, int ysize){struct SHTCTL *ctl;int i;ctl = (struct SHTCTL *) memman_alloc_4k(memman, sizeof (struct SHTCTL));if (ctl == 0) {goto err;}ctl->vram = vram;ctl->xsize = xsize;ctl->ysize = ysize;ctl->top = -1; for (i = 0; i < MAX_SHEETS; i++) {ctl->sheets0[i].flags = 0;}err:return ctl;}

5. 生成未使用的图层，从已经分配管理图层中找到一个空闲的标记占用

struct SHEET *sheet_alloc(struct SHTCTL *ctl){struct SHEET *sht;int i;for (i = 0; i < MAX_SHEETS; i++) {if (ctl->sheets0[i].flags == 0) {sht = &ctl->sheets0[i];sht->flags = SHEET_USE; sht->height = -1; return sht;}}return 0;}

6. 设置图层，指定图层显示缓存区及其大小等

void sheet_setbuf(struct SHEET *sht, unsigned char *buf, int xsize, int ysize, int col_inv){sht->buf = buf;sht->bxsize = xsize;sht->bysize = ysize;sht->col_inv = col_inv;return;}

7. 设定某个图层的高度

void sheet_updown(struct SHTCTL *ctl, struct SHEET *sht, int height){int h, old = sht->height;         /*修正高度*/if (height > ctl->top + 1) {height = ctl->top + 1;}if (height < -1) {height = -1;}sht->height = height;        /*对sheets重新排列，线性数组的前后移动操作，不难*/if (old > height) {if (height >= 0) {for (h = old; h > height; h--) {ctl->sheets[h] = ctl->sheets[h - 1];ctl->sheets[h]->height = h;}ctl->sheets[height] = sht;} else {if (ctl->top > old) {for (h = old; h < ctl->top; h++) {ctl->sheets[h] = ctl->sheets[h + 1];ctl->sheets[h]->height = h;}}ctl->top--;}sheet_refresh(ctl); } else if (old < height) {if (old >= 0) {for (h = old; h < height; h++) {ctl->sheets[h] = ctl->sheets[h + 1];ctl->sheets[h]->height = h;}ctl->sheets[height] = sht;} else {for (h = ctl->top; h >= height; h--) {ctl->sheets[h + 1] = ctl->sheets[h];ctl->sheets[h + 1]->height = h + 1;}ctl->sheets[height] = sht;ctl->top++; }sheet_refresh(ctl); }return;}

8. 刷新各图层，写入显存，这个需要优化

void sheet_refresh(struct SHTCTL *ctl){int h, bx, by, vx, vy;unsigned char *buf, c, *vram = ctl->vram;struct SHEET *sht;for (h = 0; h <= ctl->top; h++) {sht = ctl->sheets[h];buf = sht->buf;for (by = 0; by < sht->bysize; by++) {vy = sht->vy0 + by;for (bx = 0; bx < sht->bxsize; bx++) {vx = sht->vx0 + bx;c = buf[by * sht->bxsize + bx];if (c != sht->col_inv) {vram[vy * ctl->xsize + vx] = c;}}}}return;}

9. 移动图层

void sheet_slide(struct SHTCTL *ctl, struct SHEET *sht, int vx0, int vy0){sht->vx0 = vx0;sht->vy0 = vy0;if (sht->height >= 0) { sheet_refresh(ctl); }return;}

10. 释放图层

void sheet_free(struct SHTCTL* ctl,struct SHEET* sht){    if(sht->height>=0)    {        sheet_updown(ctl,sht,-1);    }    sht->flags=0;    return ;}

11.优化略（计算得到图层交叉部分重绘，其它不用绘）