Optimize Lua graphics

[toncho11]

1. We can remove luaL_checknumber() for example and replace it like that:

// only Lua 5.1
#define fast_arg_number(L, n)  (nvalue((L)->base + ((n) - 1)))
#define fast_arg_int(L, n)     ((int)fast_arg_number((L), (n)))

static int luaB_plot_line(lua_State *L)
{
    int x1 = fast_arg_int(L, 1);
    int y1 = fast_arg_int(L, 2);
    int x2 = fast_arg_int(L, 3);
    int y2 = fast_arg_int(L, 4);
    int color = fast_arg_int(L, 5);

    /* draw line here */

    return 0;
}

2. Add fill_rect(x, y, w, h, color), currently only plot_line() is available. Both the movement up/down is 2 lines as it is the ball, so we can save 2 calls in both.

We can also have a special rectangle_delta() function that both deletes and draws a rectangle. This will furhter reduce the calls, but in the best case scenario we need such function in Nano-x as well.

static void gfx_fill_rect(int x, int y, int w, int h, int color)
{
    int yy;

    if (w <= 0 || h <= 0)
        return;

    for (yy = 0; yy < h; yy++) {
        gfx_line(x, y + yy, x + w - 1, y + yy, color);
    }
}

static int luaB_rectangle_delta(lua_State *L)
{
    int rx = (int)lua_tointeger(L, 1);
    int ry = (int)lua_tointeger(L, 2);
    int rw = (int)lua_tointeger(L, 3);
    int rh = (int)lua_tointeger(L, 4);

    int ax = (int)lua_tointeger(L, 5);
    int ay = (int)lua_tointeger(L, 6);
    int aw = (int)lua_tointeger(L, 7);
    int ah = (int)lua_tointeger(L, 8);

    int fg = (int)lua_tointeger(L, 9);
    int bg = (int)lua_tointeger(L, 10);

    /* Remove old exposed part. */
    gfx_fill_rect(rx, ry, rw, rh, bg);

    /* Draw new exposed part. */
    gfx_fill_rect(ax, ay, aw, ah, fg);

    return 0;
}

3. Optimise the sleep() and event handling. This is more about design.