python - 在右下角调用 addch 时 curses 失败

Question

我开始学习 Python 中的 curses。我在 Mac OS X 上使用 Python 3.5。当我尝试在右下角写入时，程序崩溃并出现以下错误:

$ python ex_curses.py
[...]
  File "ex_curses.py", line 19, in do_curses
    screen.addch(mlines, mcols, 'c')
  _curses.error: add_wch() returned ERR

示例程序是:

import curses

def do_curses(screen):
    curses.noecho()
    curses.curs_set(0)
    screen.keypad(1)

    (line, col) = 12, 0
    screen.addstr(line, col, "Hello world!")
    line += 1
    screen.addstr(line, col, "Hello world!", curses.A_REVERSE)

    screen.addch(0, 0, "c")

    (mlines, mcols) = screen.getmaxyx()
    mlines -= 1
    mcols -= 1
    screen.addch(mlines, mcols, 'c')

    while True:
        event = screen.getch()
        if event == ord("q"):
            break
    curses.endwin()

if __name__ == "__main__":
    curses.wrapper(do_curses)

我觉得我错过了一些明显的东西，但我不知道是什么。

Answer 1

这是预期的行为(一个怪癖)，因为 addch 试图在添加一个字符后换行 到下一行。有一个 comment in lib_addch.c处理这个:

/*
 * The _WRAPPED flag is useful only for telling an application that we've just
 * wrapped the cursor.  We don't do anything with this flag except set it when
 * wrapping, and clear it whenever we move the cursor.  If we try to wrap at
 * the lower-right corner of a window, we cannot move the cursor (since that
 * wouldn't be legal).  So we return an error (which is what SVr4 does).
 * Unlike SVr4, we can successfully add a character to the lower-right corner
 * (Solaris 2.6 does this also, however).
 */