Corrections for 20021109

[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-5.3-20021109+

Here are some problems I found :

----------------------------------------------------------------------------
File : ncurses/base/tty_update.c
Function : ClearScreen (blank)

The purpose is to clear the screen with the parameter 'blank'.
The important point is 'back_color_erase' (bce) which determins if fast
clear
can be used or not.

1) 'bce' is not a function extension,  it's terminal dependant.
( The majority of terminfo entries do not specify bce - 1/10 only ).
So, 'bce' should be considered out of   #if NCURSES_EXT_FUNCS ... #endif
Considering the rest of #if NCURSES_EXT_FUNCS ... #endif itself, i don't see
the utility there.

2) There is a boolean function that tells if clear_screen / clr_eos /
clr_eol
can be used for clearing screen with 'blank', depending of 'bce', colors and
modes : 'can_clear_with()'.  Better to use it.

3) An hidden bug stay nevertheless under some conditions :
When terminal has bce FALSE (tested with linux-console, setting bce to
false), pb happens at lower right corner.
As Putchar() is used, for the lower right corner we call PutCharLR().
For linux console, we pass in :
    ..................
    } else if ((enter_insert_mode && exit_insert_mode)
           || insert_character || parm_ich) {
    GoTo(screen_lines - 1, screen_columns - 2);
    PutAttrChar(ch);
    GoTo(screen_lines - 1, screen_columns - 2);
==> InsStr(newscr->_line[screen_lines - 1].text + screen_columns - 2, 1);
    }
    ..................
Hence the bug : InsStr() inserts a char coming from newscr instead of
'blank'
while ClearScreen() modifies curscr directly with 'blank'.
This is not visible as function is static.
Need to have a function for inserting one char at cursor position.



Propose these modifs (without point 3 ):

static void ClearScreen(NCURSES_CH_T blank)
{
    int i, j;
    short fg, bg;
    bool fast_clear = (clear_screen || clr_eos || clr_eol);

    TR(TRACE_UPDATE, ("ClearScreen() called"));

==> UpdateAttrs(AttrOf(blank));  /* Taking new colors from 'blank' */
==> if (fast_clear && can_clear_with(CHREF(blank))) {
        if (clear_screen) {
            TPUTS_TRACE("clear_screen");
            putp(clear_screen);
            SP->_cursrow = SP->_curscol = 0;
            position_check(SP->_cursrow, SP->_curscol, "ClearScreen");
        }
        else if (clr_eos) {
            SP->_cursrow = SP->_curscol = -1;
            GoTo(0, 0);
            TPUTS_TRACE("clr_eos");
            putp(clr_eos);
        }
        else if (clr_eol) {
            SP->_cursrow = SP->_curscol = -1;
            for (i = 0; i < screen_lines; i++) {
                GoTo(i, 0);
                TPUTS_TRACE("clr_eol");
                putp(clr_eol);
            }
            GoTo(0, 0);
        }
    }
    else {   /* Writing 24x80 = 1920 colored chars */
        for (i = 0; i < screen_lines; i++) {
            GoTo(i, 0);
            for (j = 0; j < screen_columns; j++)
                PutChar(CHREF(blank));
        }
        GoTo(0, 0);
    }

    /* Memorize on screen changes */
    for (i = 0; i < screen_lines; i++) {
        for (j = 0; j < screen_columns; j++)
            curscr->_line[i].text[j] = blank;
    }

    TR(TRACE_UPDATE, ("screen cleared"));
}

----------------------------------------------------------------------------
File : ncurses/base/tty_update.c
Function : ClrToEOL ()

Same things, prevent using erase capabilities when 'blank' conflicts with
them or terminal not 'bce'.
Same bug at lower right corner if last line.

static void ClrToEOL (NCURSES_CH_T blank, bool needclear)
{
    int j;

    if (curscr != 0 && SP->_cursrow >= 0) {
        for (j = SP->_curscol; j < screen_columns; j++) {
            if (j >= 0) {
                NCURSES_CH_T *cp = &(curscr->_line[SP->_cursrow].text[j]);

                if (!CharEq (*cp, blank)) {
                    *cp = blank;
                    needclear = TRUE;
                }
            }
        }
    }
    else {
        needclear = TRUE;
    }

    if (needclear) {
        UpdateAttrs (AttrOf (blank));
        TPUTS_TRACE ("clr_eol");
==>     if (clr_eol && can_clear_with (CHREF (blank)) &&
==>         (SP->_el_cost <= (screen_columns - SP->_curscol))) {
==>         putp (clr_eol);
        }
        else {
            int count = (screen_columns - SP->_curscol);
            while (count-- > 0)
                PutChar (CHREF (blank));
        }
    }
}

----------------------------------------------------------------------------
- Philippe