lib_scroll.c revision 97049 
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28
29/****************************************************************************
30 *  Author: Thomas E. Dickey 1996-2001                                      *
31 *     and: Zeyd M. Ben-Halim <zmbenhal@netcom.com> 1992,1995               *
32 *     and: Eric S. Raymond <esr@snark.thyrsus.com>                         *
33 ****************************************************************************/
34
35/*
36**	lib_scroll.c
37**
38**	The routine wscrl(win, n).
39**  positive n scroll the window up (ie. move lines down)
40**  negative n scroll the window down (ie. move lines up)
41**
42*/
43
44#include <curses.priv.h>
45
46MODULE_ID("$Id: lib_scroll.c,v 1.23 2001/12/19 01:06:55 tom Exp $")
47
48NCURSES_EXPORT(void)
49_nc_scroll_window(WINDOW *win, int const n, NCURSES_SIZE_T const top,
50		  NCURSES_SIZE_T const bottom, NCURSES_CH_T blank)
51{
52    int limit;
53    int line;
54    int j;
55    size_t to_copy = (size_t) (sizeof(NCURSES_CH_T) * (win->_maxx + 1));
56
57    TR(TRACE_MOVE, ("_nc_scroll_window(%p, %d, %d, %d)", win, n, top, bottom));
58
59    if (top < 0
60	|| bottom < top
61	|| bottom > win->_maxy) {
62	TR(TRACE_MOVE, ("nothing to scroll"));
63	return;
64    }
65
66    /*
67     * This used to do a line-text pointer-shuffle instead of text copies.
68     * That (a) doesn't work when the window is derived and doesn't have
69     * its own storage, (b) doesn't save you a lot on modern machines
70     * anyway.  Your typical memcpy implementations are coded in
71     * assembler using a tight BLT loop; for the size of copies we're
72     * talking here, the total execution time is dominated by the one-time
73     * setup cost.  So there is no point in trying to be excessively
74     * clever -- esr.
75     */
76
77    /* shift n lines downwards */
78    if (n < 0) {
79	limit = top - n;
80	if (limit > win->_maxy)
81	    limit = win->_maxy;
82	for (line = bottom; line >= limit; line--) {
83	    if (line + n >= 0) {
84		TR(TRACE_MOVE, ("...copying %d to %d", line + n, line));
85		memcpy(win->_line[line].text,
86		       win->_line[line + n].text,
87		       to_copy);
88		if_USE_SCROLL_HINTS(win->_line[line].oldindex =
89				    win->_line[line + n].oldindex);
90	    } else {
91		TR(TRACE_MOVE, ("...filling %d", line));
92		for (j = 0; j <= win->_maxx; j++)
93		    win->_line[line].text[j] = blank;
94		if_USE_SCROLL_HINTS(win->_line[line].oldindex = _NEWINDEX);
95	    }
96	}
97	for (line = top; line < limit; line++) {
98	    TR(TRACE_MOVE, ("...filling %d", line));
99	    for (j = 0; j <= win->_maxx; j++)
100		win->_line[line].text[j] = blank;
101	    if_USE_SCROLL_HINTS(win->_line[line].oldindex = _NEWINDEX);
102	}
103    }
104
105    /* shift n lines upwards */
106    if (n > 0) {
107	limit = bottom - n;
108	if (limit < 0)
109	    limit = 0;
110	for (line = top; line <= limit; line++) {
111	    if (line + n <= win->_maxy) {
112		TR(TRACE_MOVE, ("...copying %d to %d", line + n, line));
113		memcpy(win->_line[line].text,
114		       win->_line[line + n].text,
115		       to_copy);
116		if_USE_SCROLL_HINTS(win->_line[line].oldindex =
117				    win->_line[line + n].oldindex);
118	    } else {
119		TR(TRACE_MOVE, ("...filling %d", line));
120		for (j = 0; j <= win->_maxx; j++)
121		    win->_line[line].text[j] = blank;
122		if_USE_SCROLL_HINTS(win->_line[line].oldindex = _NEWINDEX);
123	    }
124	}
125	for (line = bottom; line > limit; line--) {
126	    TR(TRACE_MOVE, ("...filling %d", line));
127	    for (j = 0; j <= win->_maxx; j++)
128		win->_line[line].text[j] = blank;
129	    if_USE_SCROLL_HINTS(win->_line[line].oldindex = _NEWINDEX);
130	}
131    }
132    touchline(win, top, bottom - top + 1);
133}
134
135NCURSES_EXPORT(int)
136wscrl(WINDOW *win, int n)
137{
138    T((T_CALLED("wscrl(%p,%d)"), win, n));
139
140    if (!win || !win->_scroll) {
141	TR(TRACE_MOVE, ("...scrollok is false"));
142	returnCode(ERR);
143    }
144
145    if (n == 0)
146	returnCode(OK);
147
148    _nc_scroll_window(win, n, win->_regtop, win->_regbottom, win->_nc_bkgd);
149
150    _nc_synchook(win);
151    returnCode(OK);
152}
153