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diff --git a/usr.bin/window/wwscroll.c b/usr.bin/window/wwscroll.c
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+/*
+ * Copyright (c) 1983, 1993
+ * The Regents of the University of California. All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * Edward Wang at The University of California, Berkeley.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ * must display the following acknowledgement:
+ * This product includes software developed by the University of
+ * California, Berkeley and its contributors.
+ * 4. Neither the name of the University nor the names of its contributors
+ * may be used to endorse or promote products derived from this software
+ * without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#ifndef lint
+static char sccsid[] = "@(#)wwscroll.c 8.1 (Berkeley) 6/6/93";
+#endif /* not lint */
+
+#include "ww.h"
+#include "tt.h"
+
+wwscroll(w, n)
+register struct ww *w;
+int n;
+{
+ register dir;
+ register top;
+
+ if (n == 0)
+ return;
+ dir = n < 0 ? -1 : 1;
+ top = w->ww_b.t - n;
+ if (top > w->ww_w.t)
+ top = w->ww_w.t;
+ else if (top + w->ww_b.nr < w->ww_w.b)
+ top = w->ww_w.b - w->ww_b.nr;
+ n = abs(top - w->ww_b.t);
+ if (n < w->ww_i.nr) {
+ while (--n >= 0) {
+ (void) wwscroll1(w, w->ww_i.t, w->ww_i.b, dir, 0);
+ w->ww_buf += dir;
+ w->ww_b.t -= dir;
+ w->ww_b.b -= dir;
+ }
+ } else {
+ w->ww_buf -= top - w->ww_b.t;
+ w->ww_b.t = top;
+ w->ww_b.b = top + w->ww_b.nr;
+ wwredrawwin(w);
+ }
+}
+
+/*
+ * Scroll one line, between 'row1' and 'row2', in direction 'dir'.
+ * Don't adjust ww_scroll.
+ * And don't redraw 'leaveit' lines.
+ */
+wwscroll1(w, row1, row2, dir, leaveit)
+register struct ww *w;
+int row1, row2, dir;
+int leaveit;
+{
+ register i;
+ int row1x, row2x;
+ int nvis;
+ int nvismax;
+ int scrolled = 0;
+
+ /*
+ * See how many lines on the screen are affected.
+ * And calculate row1x, row2x, and left at the same time.
+ */
+ for (i = row1; i < row2 && w->ww_nvis[i] == 0; i++)
+ ;
+ if (i >= row2) /* can't do any fancy stuff */
+ goto out;
+ row1x = i;
+ for (i = row2 - 1; i >= row1 && w->ww_nvis[i] == 0; i--)
+ ;
+ if (i <= row1x)
+ goto out; /* just one line is easy */
+ row2x = i + 1;
+
+ /*
+ * See how much of this window is visible.
+ */
+ nvismax = wwncol * (row2x - row1x);
+ nvis = 0;
+ for (i = row1x; i < row2x; i++)
+ nvis += w->ww_nvis[i];
+
+ /*
+ * If it's a good idea to scroll and the terminal can, then do it.
+ */
+ if (nvis < nvismax / 2)
+ goto no_scroll; /* not worth it */
+ if ((dir > 0 ? tt.tt_scroll_down == 0 : tt.tt_scroll_up == 0) ||
+ (tt.tt_scroll_top != row1x || tt.tt_scroll_bot != row2x - 1) &&
+ tt.tt_setscroll == 0)
+ if (tt.tt_delline == 0 || tt.tt_insline == 0)
+ goto no_scroll;
+ xxscroll(dir, row1x, row2x);
+ scrolled = 1;
+ /*
+ * Fix up the old screen.
+ */
+ {
+ register union ww_char *tmp;
+ register union ww_char **cpp, **cqq;
+
+ if (dir > 0) {
+ cpp = &wwos[row1x];
+ cqq = cpp + 1;
+ tmp = *cpp;
+ for (i = row2x - row1x; --i > 0;)
+ *cpp++ = *cqq++;
+ *cpp = tmp;
+ } else {
+ cpp = &wwos[row2x];
+ cqq = cpp - 1;
+ tmp = *cqq;
+ for (i = row2x - row1x; --i > 0;)
+ *--cpp = *--cqq;
+ *cqq = tmp;
+ }
+ for (i = wwncol; --i >= 0;)
+ tmp++->c_w = ' ';
+ }
+
+no_scroll:
+ /*
+ * Fix the new screen.
+ */
+ if (nvis == nvismax) {
+ /*
+ * Can shift whole lines.
+ */
+ if (dir > 0) {
+ {
+ register union ww_char *tmp;
+ register union ww_char **cpp, **cqq;
+
+ cpp = &wwns[row1x];
+ cqq = cpp + 1;
+ tmp = *cpp;
+ for (i = row2x - row1x; --i > 0;)
+ *cpp++ = *cqq++;
+ *cpp = tmp;
+ }
+ if (scrolled) {
+ register char *p, *q;
+
+ p = &wwtouched[row1x];
+ q = p + 1;
+ for (i = row2x - row1x; --i > 0;)
+ *p++ = *q++;
+ *p |= WWU_TOUCHED;
+ } else {
+ register char *p;
+
+ p = &wwtouched[row1x];
+ for (i = row2x - row1x; --i >= 0;)
+ *p++ |= WWU_TOUCHED;
+ }
+ wwredrawwin1(w, row1, row1x, dir);
+ wwredrawwin1(w, row2x - 1, row2 - leaveit, dir);
+ } else {
+ {
+ register union ww_char *tmp;
+ register union ww_char **cpp, **cqq;
+
+ cpp = &wwns[row2x];
+ cqq = cpp - 1;
+ tmp = *cqq;
+ for (i = row2x - row1x; --i > 0;)
+ *--cpp = *--cqq;
+ *cqq = tmp;
+ }
+ if (scrolled) {
+ register char *p, *q;
+
+ p = &wwtouched[row2x];
+ q = p - 1;
+ for (i = row2x - row1x; --i > 0;)
+ *--p = *--q;
+ *q |= WWU_TOUCHED;
+ } else {
+ register char *p;
+
+ p = &wwtouched[row1x];
+ for (i = row2x - row1x; --i >= 0;)
+ *p++ |= WWU_TOUCHED;
+ }
+ wwredrawwin1(w, row1 + leaveit, row1x + 1, dir);
+ wwredrawwin1(w, row2x, row2, dir);
+ }
+ } else {
+ if (scrolled) {
+ register char *p;
+
+ p = &wwtouched[row1x];
+ for (i = row2x - row1x; --i >= 0;)
+ *p++ |= WWU_TOUCHED;
+ }
+out:
+ if (dir > 0)
+ wwredrawwin1(w, row1, row2 - leaveit, dir);
+ else
+ wwredrawwin1(w, row1 + leaveit, row2, dir);
+ }
+ return scrolled;
+}
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