lib_scroll.c revision 62449 
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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 1.17 2000/04/29 21:10:51 tom Exp $")
46
47void
48_nc_scroll_window(WINDOW *win, int const n, NCURSES_SIZE_T const top,
49    NCURSES_SIZE_T const bottom, chtype blank)
50{
51    int line, j;
52    size_t to_copy = (size_t) (sizeof(chtype) * (win->_maxx + 1));
53
54    TR(TRACE_MOVE, ("_nc_scroll_window(%p, %d, %d, %d)", win, n, top, bottom));
55
56    /*
57     * This used to do a line-text pointer-shuffle instead of text copies.
58     * That (a) doesn't work when the window is derived and doesn't have
59     * its own storage, (b) doesn't save you a lot on modern machines
60     * anyway.  Your typical memcpy implementations are coded in
61     * assembler using a tight BLT loop; for the size of copies we're
62     * talking here, the total execution time is dominated by the one-time
63     * setup cost.  So there is no point in trying to be excessively
64     * clever -- esr.
65     */
66
67    /* shift n lines downwards */
68    if (n < 0) {
69	for (line = bottom; line >= top - n; line--) {
70	    memcpy(win->_line[line].text,
71		win->_line[line + n].text,
72		to_copy);
73	    if_USE_SCROLL_HINTS(win->_line[line].oldindex = win->_line[line
74		    + n].oldindex);
75	}
76	for (line = top; line < top - n; line++) {
77	    for (j = 0; j <= win->_maxx; j++)
78		win->_line[line].text[j] = blank;
79	    if_USE_SCROLL_HINTS(win->_line[line].oldindex = _NEWINDEX);
80	}
81    }
82
83    /* shift n lines upwards */
84    if (n > 0) {
85	for (line = top; line <= bottom - n; line++) {
86	    memcpy(win->_line[line].text,
87		win->_line[line + n].text,
88		to_copy);
89	    if_USE_SCROLL_HINTS(win->_line[line].oldindex = win->_line[line
90		    + n].oldindex);
91	}
92	for (line = bottom; line > bottom - n; line--) {
93	    for (j = 0; j <= win->_maxx; j++)
94		win->_line[line].text[j] = blank;
95	    if_USE_SCROLL_HINTS(win->_line[line].oldindex = _NEWINDEX);
96	}
97    }
98    touchline(win, top, bottom - top + 1);
99}
100
101int
102wscrl(WINDOW *win, int n)
103{
104    T((T_CALLED("wscrl(%p,%d)"), win, n));
105
106    if (!win || !win->_scroll)
107	returnCode(ERR);
108
109    if (n == 0)
110	returnCode(OK);
111
112    if ((n > (win->_regbottom - win->_regtop)) ||
113	(-n > (win->_regbottom - win->_regtop)))
114	returnCode(ERR);
115
116    _nc_scroll_window(win, n, win->_regtop, win->_regbottom, _nc_background(win));
117
118    _nc_synchook(win);
119    returnCode(OK);
120}
121