Corrections for 20021019

[Philippe Blain]

>From Philippe Blain, Bordeaux, FRANCE.
My old computer: P133 - 8,4 Go - 32 Mo Red Hat Linux 7.0

To maintainers of 'ncurses'.(and to Mr Dickey)
Subject: Corrections for ncurses-5.3-20021019+

Here are some problems I found :

----------------------------------------------------------------------------
File : ncurses/base/lib_screen.c

Function : scr_dump(const char *file)

If file does not exist, _nc_access fails and return -1, preventing from
dumping to a new file.
    ..................
    if (_nc_access(file, W_OK) < 0 || (fp = fopen(file, "wb")) == 0) {
    returnCode(ERR);
    ..................

----------------------------------------------------------------------------
File : ncurses/tty/lib_mvcur.c

Macro definition :
      #define NOT_LOCAL(fy, fx, ty, tx) ((tx > LONG_DIST) &&\
 (tx < screen_lines - 1 - LONG_DIST) && (abs(ty-fy) + abs(tx-fx) >
LONG_DIST)

should be 'screen_columns' instead of 'screen_lines', I think (x-axis).

----------------------------------------------------------------------------
File : ncurses/base/lib_scroll.c

Function : _nc_scroll_window()

Function is not good since introduction of 'limit'.
NEWS - 20011020
    + rewrote limit-checks in wscrl() and associated _nc_scroll_window(),
      to ensure that if the parameter of wscrl() is larger than the size of
      the scrolling region, then the scrolling region will be cleared
      (report by Ben Kohlen <address@hidden>).


EXAMPLES :

I suppose a 24 * 80 window (full screen)
Take for scrolling region : top = 10, bottom = 20

1) n = -12 (n larger than scrolling region)
This gives limit = 10 - (-12) = 22
and then function blanks lines 10 to 22 (==> OUT OF REGION)

2) n = +12
This gives limit = 20 - 12 = 8
and then function blanks lines 8 to 20 (==> OUT OF REGION)

3) n = -6 (normal case)
    Gives limit = 10 - (-6) = 16
Algorithm :
    for (line = 20; line >= 16; line--)
        if (line - 6 >= 0)  /* always true because of the loop interval */
            copy (line - 6) in line;
        else
            blank line;  /* never executed */
    for (line = 10; line <= 16; line++)
        blank line;

4) n = +6
    Gives limit = 20 - 6 = 14
Algorithm :
    for (line = 10; line <= 14; line++)
        if (line + 6 < 23)  /* always true because of the loop interval */
            copy (line + 6) in line;
        else
            blank line;  /* never executed */
    for (line = 20; line > 14; line--)
        blank line;


#####>  Propose to simplify code in 2 cases:
       abs(n) < scrolling region     abs(n) >= scrolling region

NCURSES_EXPORT (void)
_nc_scroll_window (WINDOW * win, int const n, NCURSES_SIZE_T const top,
                   NCURSES_SIZE_T const bottom, NCURSES_CH_T blank)
{
    int line;
    int j;
    size_t to_copy = (size_t) (sizeof (NCURSES_CH_T) * (win->_maxx + 1));

    TR (TRACE_MOVE,
        ("_nc_scroll_window(%p, %d, %d, %d)", win, n, top, bottom));

==> if (n == 0 || top < 0 || bottom < top || bottom > win->_maxy) {
        TR (TRACE_MOVE, ("nothing to scroll"));
        return;
    }

==> if (abs (n) < bottom - top + 1) {
        /* shift n lines downwards */
        if (n < 0) {
            for (line = bottom; line >= top - n; line--) {
                TR (TRACE_MOVE, ("...copying %d to %d", line + n, line));
                memcpy (win->_line[line].text,
                        win->_line[line + n].text, to_copy);
                if_USE_SCROLL_HINTS (win->_line[line].oldindex =
                                     win->_line[line + n].oldindex);
            }
            for (line = top; line < top - n; line++) {
                TR (TRACE_MOVE, ("...filling %d", line));
                for (j = 0; j <= win->_maxx; j++)
                    win->_line[line].text[j] = blank;
                if_USE_SCROLL_HINTS (win->_line[line].oldindex = _NEWINDEX);
            }
        }

        /* shift n lines upwards */
        if (n > 0) {
            for (line = top; line <= bottom - n; line++) {
                TR (TRACE_MOVE, ("...copying %d to %d", line + n, line));
                memcpy (win->_line[line].text,
                        win->_line[line + n].text, to_copy);
                if_USE_SCROLL_HINTS (win->_line[line].oldindex =
                                     win->_line[line + n].oldindex);
            }
            for (line = bottom; line > bottom - n; line--) {
                TR (TRACE_MOVE, ("...filling %d", line));
                for (j = 0; j <= win->_maxx; j++)
                    win->_line[line].text[j] = blank;
                if_USE_SCROLL_HINTS (win->_line[line].oldindex = _NEWINDEX);
            }
        }
    }
==> /* Blanking the whole window */
    else {
        for (line = top; line <= bottom; line++) {
            TR (TRACE_MOVE, ("...filling %d", line));
            for (j = 0; j <= win->_maxx; j++)
                win->_line[line].text[j] = blank;
            if_USE_SCROLL_HINTS (win->_line[line].oldindex = _NEWINDEX);
        }
    }
    touchline (win, top, bottom - top + 1);
}

#####>  As I write this, I think to another (bad) idea :
    And what about scrolling a pad, huh ???
----------------------------------------------------------------------------
- Philippe - ncurses-6.0 will be the good one ! :-))