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 256 struct 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_USE 1 struct 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)