1/****************************************************************************
2 * Copyright 2019,2020 Thomas E. Dickey                                     *
3 * Copyright 1998-2010,2011 Free Software Foundation, Inc.                  *
4 *                                                                          *
5 * Permission is hereby granted, free of charge, to any person obtaining a  *
6 * copy of this software and associated documentation files (the            *
7 * "Software"), to deal in the Software without restriction, including      *
8 * without limitation the rights to use, copy, modify, merge, publish,      *
9 * distribute, distribute with modifications, sublicense, and/or sell       *
10 * copies of the Software, and to permit persons to whom the Software is    *
11 * furnished to do so, subject to the following conditions:                 *
12 *                                                                          *
13 * The above copyright notice and this permission notice shall be included  *
14 * in all copies or substantial portions of the Software.                   *
15 *                                                                          *
16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS  *
17 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF               *
18 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.   *
19 * IN NO EVENT SHALL THE ABOVE COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,   *
20 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR    *
21 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR    *
22 * THE USE OR OTHER DEALINGS IN THE SOFTWARE.                               *
23 *                                                                          *
24 * Except as contained in this notice, the name(s) of the above copyright   *
25 * holders shall not be used in advertising or otherwise to promote the     *
26 * sale, use or other dealings in this Software without prior written       *
27 * authorization.                                                           *
28 ****************************************************************************/
29
30/****************************************************************************
31 *  Author: Thomas E. Dickey 1996-2003                                      *
32 *     and: Zeyd M. Ben-Halim <zmbenhal@netcom.com> 1992,1995               *
33 *     and: Eric S. Raymond <esr@snark.thyrsus.com>                         *
34 ****************************************************************************/
35
36/*
37**	lib_scroll.c
38**
39**	The routine wscrl(win, n).
40**  positive n scroll the window up (ie. move lines down)
41**  negative n scroll the window down (ie. move lines up)
42**
43*/
44
45#include <curses.priv.h>
46
47MODULE_ID("$Id: lib_scroll.c,v 1.32 2020/02/02 23:34:34 tom Exp $")
48
49NCURSES_EXPORT(void)
50_nc_scroll_window(WINDOW *win,
51		  int const n,
52		  int const top,
53		  int const bottom,
54		  NCURSES_CH_T blank)
55{
56    int limit;
57    int line;
58    int j;
59    size_t to_copy = (sizeof(NCURSES_CH_T) * (size_t) (win->_maxx + 1));
60
61    TR(TRACE_MOVE, ("_nc_scroll_window(%p, %d, %ld, %ld)",
62		    (void *) win, n, (long) top, (long) bottom));
63
64    if (top < 0
65	|| bottom < top
66	|| bottom > win->_maxy) {
67	TR(TRACE_MOVE, ("nothing to scroll"));
68	return;
69    }
70
71    /*
72     * This used to do a line-text pointer-shuffle instead of text copies.
73     * That (a) doesn't work when the window is derived and doesn't have
74     * its own storage, (b) doesn't save you a lot on modern machines
75     * anyway.  Your typical memcpy implementations are coded in
76     * assembler using a tight BLT loop; for the size of copies we're
77     * talking here, the total execution time is dominated by the one-time
78     * setup cost.  So there is no point in trying to be excessively
79     * clever -- esr.
80     */
81#define BottomLimit(n) ((n) >= 0 && (n) >= top)
82#define TopLimit(n)    ((n) <= win->_maxy && (n) <= bottom)
83
84    /* shift n lines downwards */
85    if (n < 0) {
86	limit = top - n;
87	for (line = bottom; line >= limit && BottomLimit(line); line--) {
88	    TR(TRACE_MOVE, ("...copying %d to %d", line + n, line));
89	    memcpy(win->_line[line].text,
90		   win->_line[line + n].text,
91		   to_copy);
92	    if_USE_SCROLL_HINTS(win->_line[line].oldindex =
93				win->_line[line + n].oldindex);
94	}
95	for (line = top; line < limit && TopLimit(line); line++) {
96	    TR(TRACE_MOVE, ("...filling %d", line));
97	    for (j = 0; j <= win->_maxx; j++)
98		win->_line[line].text[j] = blank;
99	    if_USE_SCROLL_HINTS(win->_line[line].oldindex = _NEWINDEX);
100	}
101    }
102
103    /* shift n lines upwards */
104    if (n > 0) {
105	limit = bottom - n;
106	for (line = top; line <= limit && TopLimit(line); line++) {
107	    memcpy(win->_line[line].text,
108		   win->_line[line + n].text,
109		   to_copy);
110	    if_USE_SCROLL_HINTS(win->_line[line].oldindex =
111				win->_line[line + n].oldindex);
112	}
113	for (line = bottom; line > limit && BottomLimit(line); line--) {
114	    for (j = 0; j <= win->_maxx; j++)
115		win->_line[line].text[j] = blank;
116	    if_USE_SCROLL_HINTS(win->_line[line].oldindex = _NEWINDEX);
117	}
118    }
119    touchline(win, top, bottom - top + 1);
120
121    if_WIDEC({
122	if (WINDOW_EXT(win, addch_used) != 0) {
123	    int next = WINDOW_EXT(win, addch_y) + n;
124	    if (next < 0 || next > win->_maxy) {
125		TR(TRACE_VIRTPUT,
126		   ("Alert discarded multibyte on scroll"));
127		WINDOW_EXT(win, addch_y) = 0;
128	    } else {
129		TR(TRACE_VIRTPUT, ("scrolled working position to %d,%d",
130				   WINDOW_EXT(win, addch_y),
131				   WINDOW_EXT(win, addch_x)));
132		WINDOW_EXT(win, addch_y) = next;
133	    }
134	}
135    })
136}
137
138NCURSES_EXPORT(int)
139wscrl(WINDOW *win, int n)
140{
141    T((T_CALLED("wscrl(%p,%d)"), (void *) win, n));
142
143    if (!win || !win->_scroll) {
144	TR(TRACE_MOVE, ("...scrollok is false"));
145	returnCode(ERR);
146    }
147
148    if (n != 0) {
149	_nc_scroll_window(win, n, win->_regtop, win->_regbottom, win->_nc_bkgd);
150	_nc_synchook(win);
151    }
152    returnCode(OK);
153}
154