lib_scroll.c revision 76726 
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28
29/****************************************************************************
30 *  Author: Zeyd M. Ben-Halim <zmbenhal@netcom.com> 1992,1995               *
31 *     and: Eric S. Raymond <esr@snark.thyrsus.com>                         *
32 ****************************************************************************/
33
34/*
35**	lib_scroll.c
36**
37**	The routine wscrl(win, n).
38**  positive n scroll the window up (ie. move lines down)
39**  negative n scroll the window down (ie. move lines up)
40**
41*/
42
43#include <curses.priv.h>
44
45MODULE_ID("$Id: lib_scroll.c,v 1.20 2000/12/10 02:54:03 tom Exp $")
46
47NCURSES_EXPORT(void)
48_nc_scroll_window
49(WINDOW *win, int const n, NCURSES_SIZE_T const top,
50 NCURSES_SIZE_T const bottom, chtype blank)
51{
52    int line, j;
53    size_t to_copy = (size_t) (sizeof(chtype) * (win->_maxx + 1));
54
55    TR(TRACE_MOVE, ("_nc_scroll_window(%p, %d, %d, %d)", win, n, top, bottom));
56
57    /*
58     * This used to do a line-text pointer-shuffle instead of text copies.
59     * That (a) doesn't work when the window is derived and doesn't have
60     * its own storage, (b) doesn't save you a lot on modern machines
61     * anyway.  Your typical memcpy implementations are coded in
62     * assembler using a tight BLT loop; for the size of copies we're
63     * talking here, the total execution time is dominated by the one-time
64     * setup cost.  So there is no point in trying to be excessively
65     * clever -- esr.
66     */
67
68    /* shift n lines downwards */
69    if (n < 0) {
70	for (line = bottom; line >= top - n; line--) {
71	    memcpy(win->_line[line].text,
72		   win->_line[line + n].text,
73		   to_copy);
74	    if_USE_SCROLL_HINTS(
75				   win->_line[line].oldindex =
76				   win->_line[line + n].oldindex);
77	}
78	for (line = top; line < top - n; line++) {
79	    for (j = 0; j <= win->_maxx; j++)
80		win->_line[line].text[j] = blank;
81	    if_USE_SCROLL_HINTS(win->_line[line].oldindex = _NEWINDEX);
82	}
83    }
84
85    /* shift n lines upwards */
86    if (n > 0) {
87	for (line = top; line <= bottom - n; line++) {
88	    memcpy(win->_line[line].text,
89		   win->_line[line + n].text,
90		   to_copy);
91	    if_USE_SCROLL_HINTS(win->_line[line].oldindex =
92				win->_line[line + n].oldindex);
93	}
94	for (line = bottom; line > bottom - n; line--) {
95	    for (j = 0; j <= win->_maxx; j++)
96		win->_line[line].text[j] = blank;
97	    if_USE_SCROLL_HINTS(win->_line[line].oldindex = _NEWINDEX);
98	}
99    }
100    touchline(win, top, bottom - top + 1);
101}
102
103NCURSES_EXPORT(int)
104wscrl(WINDOW *win, int n)
105{
106    T((T_CALLED("wscrl(%p,%d)"), win, n));
107
108    if (!win || !win->_scroll)
109	returnCode(ERR);
110
111    if (n == 0)
112	returnCode(OK);
113
114    if ((n > (win->_regbottom - win->_regtop)) ||
115	(-n > (win->_regbottom - win->_regtop)))
116	returnCode(ERR);
117
118    _nc_scroll_window(win, n, win->_regtop, win->_regbottom, _nc_background(win));
119
120    _nc_synchook(win);
121    returnCode(OK);
122}
123