cpp/bgi/demo_bgi.cpp · 10876 字节 · 下载原文

// demo_bgi.cpp —— **第 3 层：传统图形接口**（BGI / Borland Graphics Interface）

// demo_bgi.cpp — **Layer 3: the classic graphics interface** (BGI / Borland Graphics Interface)

//

// 与 `Examples/c/demo_bgi.c` 是**同一个画面、同一套接口**，用 C++ 前端再编一遍。

// It is **the same picture with the same interface** as `Examples/c/demo_bgi.c`, just compiled again with the C++ frontend.

// C 与 C++ 是两个独立前端，同一份源码两边行为不保证一致，所以两份都要有

// C and C++ are two independent frontends, and the same source is not guaranteed to behave the same on both, so both copies are needed

// （`test_bgi.c` / `test_bgi.cpp` 一直是**逐字节相同**的两份，就是这个理由）。

// (that is also why `test_bgi.c` / `test_bgi.cpp` have always been two **byte-identical** copies).

//

// ## 这一层的两个特点

// ## Two traits of this layer

//

//   · **固定分辨率**：开一次 `VGAHI` 就是 640×480，程序里到处写死坐标。

//   · **Fixed resolution**: opening `VGAHI` once means 640×480, and coordinates are hardcoded all over the program.

//     宿主负责把这块固定画布摆到真实屏幕上（本平台走 `ui_win_open_pc`，不随旋转重排）。

//     The host is responsible for placing this fixed canvas onto the real screen (on this platform it goes through `ui_win_open_pc` and is not re-laid-out on rotation).

//   · **索引色**：`setcolor(4)` 说的是「红」，不是 RGB `0x000004`。全套 16 个色号。

//   · **Indexed colors**: `setcolor(4)` means "red", not the RGB value `0x000004`. A full set of 16 color numbers.

//

// `Lib/c/graphics.h` 把 BGI 的**函数名与语义**原样接过来，落笔换成平台的 `ui_*`。

// `Lib/c/graphics.h` takes BGI's **function names and semantics** over as-is, and swaps the actual drawing for the platform's `ui_*`.

// C++ 的 include 路径包含 `Lib/c`，所以 `#include <graphics.h>` 两边是**同一份**

// The C++ include path contains `Lib/c`, so `#include <graphics.h>` is **the same file** on both sides

// （C++ 没有自己的 BGI 头，也不需要 —— 这一层就是 C 的接口）。

// (C++ has no BGI header of its own, and needs none — this layer is simply the C interface).

//

// ## ⚠ 不调 `getch()` 收尾

// ## ⚠ Do not call `getch()` at the end

//

// 老程序常见的结尾是 `getch(); closegraph();`。`conio` 的 `getch()` 在本平台是"按行"的，

// The common ending in old programs is `getch(); closegraph();`. On this platform `conio`'s `getch()` is line-based,

// 图形窗口里按不了键 —— 调它会把程序挂在 `--timeout` 上（实测 30 秒）才结束。

// and you cannot press keys inside a graphics window — calling it hangs the program until `--timeout` (measured: 30 seconds) before it ends.

// 所以画完直接 `closegraph()`，正常返回。

// So after drawing, just call `closegraph()` and return normally.

//

// 跑法：命令行页输入  vml run examples/cpp/demo_bgi.cpp

// How to run: type  vml run examples/cpp/demo_bgi.cpp  on the command-line page

// 出图：vmlcli Examples/cpp/demo_bgi.cpp --frames /tmp/fr

// Frames: vmlcli Examples/cpp/demo_bgi.cpp --frames /tmp/fr


#include <vml_ui.h>
#include <graphics.h>

#define VBAR_X 40
#define VBAR_Y 92

int main()
{
    int gd = DETECT;
    int gm = 0;
    int i;
    int x, y;
    int tri[8];
    // 界面语言：开局查一次（`ui_scr_get_language` 是 syscall，别每帧调）—— 文案按它取

    // UI language: queried once at startup (`ui_scr_get_language` is a syscall, do not call it every frame) — the text is picked by it

    int Lang = ui_scr_get_language();

    // ── 1. 开场三行（DETECT ⇒ 库自己挑，本平台挑出 VGA + VGAHI 640×480）──

    // ── 1. Three opening lines (DETECT ⇒ the library picks for itself; here it picks VGA + VGAHI 640×480) ──

    initgraph(&gd, &gm, "");

    // ── 2. 铺底：`cleardevice` 整屏刷成当前背景色 ──

    // ── 2. Background: `cleardevice` floods the whole screen with the current background color ──

    setbkcolor(BLACK);
    cleardevice();

    // ── 3. 标题（索引 14 = 黄；字号 3 = 3×16 像素）──

    // ── 3. Title (index 14 = yellow; font size 3 = 3×16 pixels) ──

    setcolor(YELLOW);
    settextstyle(DEFAULT_FONT, HORIZ_DIR, 3);
    // ⚠ 竖档必须写 `TOP_TEXT`（**盒顶**落在 y），**不能写 0** —— 0 是 `BOTTOM_TEXT`

    // ⚠ The vertical setting must be `TOP_TEXT` (**box top** at y), and **must not be 0** — 0 is `BOTTOM_TEXT`

    //   （盒**底**落在 y）。字号 3 的盒高是 48px，写 0 的话整块标题被顶到屏幕外、

    //   (box **bottom** at y). The box height at font size 3 is 48px, so writing 0 pushes the whole title off the screen,

    //   只剩底部十来行可见（`outtextxy` 的 y 是**盒顶**，这是 BGI 的缺省对齐）。

    //   leaving only the bottom dozen or so lines visible (`outtextxy`'s y is the **box top**, which is BGI's default alignment).

    settextjustify(CENTER_TEXT, TOP_TEXT);
    outtextxy(getmaxx() / 2, 12, Lang == 0 ? "BGI 传统图形接口 / demo_bgi.cpp" : "BGI legacy graphics API / demo_bgi.cpp");
    settextstyle(DEFAULT_FONT, HORIZ_DIR, 1);
    // `0` = `BOTTOM_TEXT`：正文行按"盒底贴着 y"排。

    // `0` = `BOTTOM_TEXT`: body lines are laid out with the box bottom against y.

    // ⚠ **别改成 `TOP_TEXT`** —— 那会把下面每一行整体再下移约 13px，底部会被顶出画布。

    // ⚠ **Do not change it to `TOP_TEXT`** — that shifts every line below down by about another 13px and pushes the bottom off the canvas.

    settextjustify(LEFT_TEXT, 0);

    // y 取 74（不是 62）：上面那行标题按 TOP 排时盒子占到 y=60，得给它让出位置

    // y is 74 (not 62): laid out with TOP, the title line above occupies the box up to y=60, so we have to leave room for it

    setcolor(LIGHTGRAY);
    outtextxy(20, 74, "fixed resolution 640x480, 16-color indexed palette (setcolor 0..15)");

    // ── 4. 16 色色带（这一层「索引色」最直观的一张图）──

    // ── 4. The 16-color band (the most direct picture of "indexed colors" in this layer) ──

    for (i = 0; i < 16; i++) {
        setfillstyle(SOLID_FILL, i);
        bar(VBAR_X + i * 34, VBAR_Y, VBAR_X + i * 34 + 30, VBAR_Y + 34);
    }
    setcolor(WHITE);
    rectangle(VBAR_X - 1, VBAR_Y - 1, VBAR_X + 16 * 34 + 1, VBAR_Y + 35);
    setcolor(LIGHTGRAY);
    outtextxy(VBAR_X, VBAR_Y + 50, "0 black  1 blue  2 green  3 cyan  4 red  5 magenta  6 brown  7 lightgray");
    outtextxy(VBAR_X, VBAR_Y + 66, "8 darkgray  9 lightblue  10 lightgreen  11 lightcyan  12 lightred  13 lightmagenta  14 yellow  15 white");

    // ── 5. 直线 / 折线（moveto + lineto / linerel 是老程序的常规姿势）──

    // ── 5. Lines / polylines (moveto + lineto / linerel is the usual posture of old programs) ──

    setcolor(LIGHTGREEN);
    line(40, 210, 200, 210);
    moveto(40, 230);
    lineto(120, 230);
    linerel(80, 0);
    setcolor(LIGHTCYAN);
    moveto(40, 250);
    linerel(40, -20);
    linerel(40, 20);
    linerel(40, -20);
    linerel(40, 20);
    setcolor(LIGHTGRAY);
    outtextxy(40, 262, "line / moveto / lineto / linerel (polyline is open)");

    // ── 6. 矩形与两种"条" ──

    // ── 6. Rectangles and the two kinds of "bar" ──

    setcolor(YELLOW);
    rectangle(250, 205, 370, 265);
    setfillstyle(SOLID_FILL, LIGHTBLUE);
    bar(380, 205, 450, 265);
    setfillstyle(SOLID_FILL, GREEN);
    setcolor(WHITE);
    bar3d(465, 215, 545, 265, 14, 1);
    setcolor(LIGHTGRAY);
    outtextxy(250, 272, "rectangle / bar / bar3d");

    // ── 7. 圆与椭圆 ──

    // ── 7. Circles and ellipses ──

    setcolor(LIGHTMAGENTA);
    circle(80, 330, 40);
    circle(80, 330, 24);
    setfillstyle(SOLID_FILL, BROWN);
    fillellipse(200, 330, 56, 34);
    setcolor(LIGHTGRAY);
    ellipse(200, 330, 0, 360, 70, 44);
    outtextxy(40, 388, "circle / fillellipse / ellipse");

    // ── 8. 弧与扇形（只有"刷子接口"画得了这两样，见 graphics.h 的说明）──

    // ── 8. Arcs and pies (only the "brush interface" can draw these two; see the notes in graphics.h) ──

    setcolor(LIGHTRED);
    arc(330, 330, 30, 150, 40);
    setcolor(WHITE);
    setfillstyle(SOLID_FILL, YELLOW);
    pieslice(420, 330, 200, 340, 40);
    setcolor(LIGHTGRAY);
    outtextxy(290, 388, "arc (stroke) / pieslice (filled)");

    // ── 9. 多边形（⚠ BGI 的顶点表**首点要重复一次**才闭合，老规矩）──

    // ── 9. Polygons (⚠ in BGI the vertex list **must repeat the first point** to close, an old rule) ──

    tri[0] = 520;   tri[1] = 370;
    tri[2] = 560;   tri[3] = 300;
    tri[4] = 600;   tri[5] = 370;
    tri[6] = tri[0]; tri[7] = tri[1];
    setcolor(LIGHTGREEN);
    drawpoly(4, tri);
    setfillstyle(SOLID_FILL, LIGHTMAGENTA);
    setcolor(WHITE);
    fillpoly(4, tri);
    setcolor(LIGHTGRAY);
    outtextxy(520, 388, "drawpoly / fillpoly");

    // ── 10. 像素与读回 ──

    // ── 10. Pixels and read-back ──

    for (y = 0; y < 6; y++) {
        for (x = 0; x < 16; x++) {
            // 棋盘格：两种索引色交替，一眼看出 putpixel 生效了

            // Checkerboard: two indexed colors alternating, so you can see at a glance that putpixel took effect

            if ((x + y) % 2 == 0) {
                setcolor(WHITE);
            } else {
                setcolor(BLUE);
            }
            putpixel(60 + x * 8, 410 + y * 8, getcolor());
        }
    }
    setcolor(LIGHTGRAY);
    outtextxy(40, 466, "putpixel / getcolor");

    // ── 11. 三档对齐（老程序居中排版靠 settextjustify）──

    // ── 11. The three alignment settings (old programs center their layout with settextjustify) ──

    setcolor(WHITE);
    settextstyle(DEFAULT_FONT, HORIZ_DIR, 2);
    settextjustify(LEFT_TEXT, 0);
    outtextxy(300, 405, "LEFT");
    settextjustify(CENTER_TEXT, 0);
    outtextxy(430, 405, "CENTER");
    settextjustify(RIGHT_TEXT, 0);
    outtextxy(620, 405, "RIGHT");
    settextstyle(DEFAULT_FONT, HORIZ_DIR, 1);
    settextjustify(LEFT_TEXT, 0);
    outtextxy(300, 430, "settextstyle(size) + settextjustify(LEFT/CENTER/RIGHT)");

    // ── 12. 收尾（不调 getch()，理由见文件头）──

    // ── 12. Wrap-up (no getch() call; see the file header for why) ──

    ui_2d_present();
    closegraph();
    return 0;
}