first version of scroll from Roberto E. Vargas Caballero

https://lists.suckless.org/dev/1703/31256.html

scroll.c

@@ -0,0 +1,188 @@
+#define _DEFAULT_SOURCE
+#include <stdio.h>
+#include <termios.h>
+#include <sys/ioctl.h>
+#include <sys/select.h>
+#include <stdlib.h>
+#include <pty.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <stdarg.h>
+#include <string.h>
+#include <signal.h>
+#include <sys/wait.h>
+#include <errno.h>
+
+typedef struct Line Line;
+struct Line {
+	Line *next;
+	Line *prev;
+	size_t len;
+	char str[];
+};
+
+pid_t child;
+int mfd;
+struct termios dfl;
+struct winsize ws;
+Line *lines, *bottom;
+
+void
+die(const char *fmt, ...)
+{
+	va_list ap;
+	va_start(ap, fmt);
+	vfprintf(stderr, fmt, ap);
+	va_end(ap);
+	if (fmt[0] && fmt[strlen(fmt)-1] == ':') {
+		fputc(' ', stderr);
+		perror(NULL);
+	} else {
+		fputc('\n', stderr);
+	}
+	exit(1);
+}
+
+void
+sigchld(int sig)
+{
+	pid_t pid;
+	while ((pid = waitpid(-1, NULL, WNOHANG)) > 0)
+		if (pid == child)
+			die("child died");
+}
+
+void
+sigwinch(int sig)
+{
+	if (ioctl(1, TIOCGWINSZ, &ws) < 0)
+		die("ioctl:");
+	if (ioctl(mfd, TIOCSWINSZ, &ws) < 0)
+		die("ioctl:");
+	kill(-child, SIGWINCH);
+}
+
+void
+reset(void)
+{
+	if (tcsetattr(0, TCSANOW, &dfl) < 0)
+		die("tcsetattr:");
+}
+
+void
+addline(char *str)
+{
+	size_t len = strchr(str, '\n') - str + 1;
+	Line *lp = malloc(sizeof(*lp) + len * sizeof(*lp->str));
+
+	if (!lp)
+		die("malloc:");
+	memcpy(lp->str, str, len);
+	lp->len = len;
+	if (lines)
+		lines->next = lp;
+	lp->prev = lines;
+	lp->next = NULL;
+	bottom = lines = lp;
+}
+
+void
+scrollup(void)
+{
+	Line *lp;
+	int rows = ws.ws_row-1;
+	int cols = ws.ws_col;
+
+	if (!bottom || !(bottom = bottom->prev))
+		return;
+
+	for (lp = bottom; lp && rows > 0; lp = lp->prev)
+		rows -= lp->len / cols + 1;
+
+	if (rows < 0) {
+		write(1, lp->str + -rows * cols, lp->len - -rows * cols);
+		rows = 0;
+		lp = lp->next;
+	}
+
+	for (; lp && lp != bottom->next; lp = lp->next)
+		write(1, lp->str, lp->len);
+}
+
+int
+main(int argc, char *argv[])
+{
+	if (argc <= 1)
+		die("usage");
+
+	if (tcgetattr(0, &dfl) < 0)
+		die("tcgetattr:");
+	if (atexit(reset))
+		die("atexit:");
+
+	if (ioctl(1, TIOCGWINSZ, &ws) < 0)
+		die("ioctl:");
+
+	child = forkpty(&mfd, NULL, &dfl, &ws);
+	if (child < 0)
+		die("forkpty:");
+	if (!child) {
+		execvp(argv[1], argv + 1);
+		perror("execvp");
+		_exit(127);
+	}
+
+	if (signal(SIGCHLD, sigchld) == SIG_ERR)
+		die("signal:");
+	if (signal(SIGWINCH, sigwinch) == SIG_ERR)
+		die("signal:");
+
+	int f;
+	if ((f = fcntl(mfd, F_GETFL)) < 0)
+		die("fcntl:");
+	if (fcntl(mfd, F_SETFL, f /*| O_NONBLOCK*/) < 0)
+		die("fcntl:");
+
+	struct termios new;
+	new = dfl;
+	cfmakeraw(&new);
+	new.c_cc[VMIN ] = 1;
+	new.c_cc[VTIME] = 0;
+	if (tcsetattr(0, TCSANOW, &new) < 0)
+		die("tcsetattr:");
+
+	fd_set rd;
+	char buf[10000], *p = buf;
+	for (;;) {
+		char c;
+
+		FD_ZERO(&rd);
+		FD_SET(  0, &rd);
+		FD_SET(mfd, &rd);
+
+		if (select(mfd + 1, &rd, NULL, NULL, NULL) < 0 && errno != EINTR)
+			die("select:");
+
+		if (FD_ISSET(0, &rd)) {
+			if (read(0, &c, 1) <= 0 && errno != EINTR)
+				die("read:");
+			if (c == 17) /* ^Q */
+				scrollup();
+			else if (write(mfd, &c, 1) < 0)
+				die("write:");
+		}
+		if (FD_ISSET(mfd, &rd)) {
+			if (read(mfd, &c, 1) <= 0 && errno != EINTR)
+				die("read:");
+			*p++ = c;
+			if (c == '\n') {
+				p = buf;
+				addline(buf);
+			}
+			if (write(1, &c, 1) < 0)
+				die("write:");
+		}
+	}
+	return 0;
+}