From 1a99270e6d3e6a519b33b4deef749bdd55ccce1c Mon Sep 17 00:00:00 2001
From: Kaz Kylheku <kaz@kylheku.com>
Date: Thu, 28 Apr 2022 19:03:39 -0700
Subject: Implement Ctrl-Z suspend.

---
 pw.1 | 14 ++++++++++++--
 pw.c | 33 +++++++++++++++++++++++++++------
 2 files changed, 39 insertions(+), 8 deletions(-)

diff --git a/pw.1 b/pw.1
index 5c0240e..7fe38a4 100644
--- a/pw.1
+++ b/pw.1
@@ -217,6 +217,18 @@ recall using the up and down arrow keys or
 and
 .BR Ctrl-N .
 
+.IP \fBCtrl-Z\fI
+Suspends
+.IR pw ,
+and indeed the entire surrounding process group, to the background
+to gain shell access. This requires a job control shell.
+When
+.IR pw
+is foregrounded again, it will refresh the display in a new text area below the
+cursor, avoiding overwriting anything in the terminal. Thus suspending and then
+immediately foregrounding provides a way to save a snapshot of the window into
+the terminal sessions history.
+
 .SH COLON COMMANDS
 
 First, some general remarks. Display refresh doesn't pause during the editing
@@ -365,8 +377,6 @@ The intervals and number of lines cannot be dynamically adjusted.
 There is no support for unwrapping long lines, which would be useful for
 copy and paste.
 
-Ctrl-Z suspend is missing.
-
 During the
 .B :!
 command's execution, the TTY settings are not restored.
diff --git a/pw.c b/pw.c
index f3c4c34..eb4c425 100644
--- a/pw.c
+++ b/pw.c
@@ -13,6 +13,7 @@
 #include <sys/time.h>
 #include <fcntl.h>
 #include <errno.h>
+#include <signal.h>
 #include <regex.h>
 
 #define ctrl(ch) ((ch) & 0x1f)
@@ -396,6 +397,18 @@ static void execute(char *cmd, unsigned *pstat)
   fflush(stdout);
 }
 
+static void ttyset(int fd, struct termios *tty)
+{
+  if (tcsetattr(fd, TCSANOW, tty) < 0)
+    panic("unable to set TTY parameters");
+}
+
+static void ttyget(int fd, struct termios *tty)
+{
+  if (tcgetattr(fd, tty) < 0)
+    panic("unable to get TTY parameters");
+}
+
 int main(int argc, char **argv)
 {
   char *line = 0;
@@ -471,8 +484,7 @@ int main(int argc, char **argv)
     columns = ws.ws_col;
   }
 
-  if (tcgetattr(ttyfd, &tty_saved) < 0)
-    panic("unable to get TTY parameters");
+  ttyget(ttyfd, &tty_saved);
 
   tty_new = tty_saved;
 
@@ -483,8 +495,7 @@ int main(int argc, char **argv)
   tty_new.c_cc[VMIN] = 1;
   tty_new.c_cc[VTIME] = 0;
 
-  if (tcsetattr(ttyfd, TCSANOW, &tty_new) < 0)
-    panic("unable to set TTY parameters");
+  ttyset(ttyfd, &tty_new);
 
   setvbuf(tty, NULL, _IONBF, 0);
 
@@ -614,6 +625,17 @@ int main(int argc, char **argv)
       if ((pe[0].revents)) {
         int ch = getc(tty);
 
+        if (ch == ctrl('z')) {
+          ttyset(ttyfd, &tty_saved);
+          kill(0, SIGTSTP);
+          ttyset(ttyfd, &tty_new);
+          for (int i = 0; i < nlines; i++)
+            puts("");
+          redraw(circbuf, nlines, hpos, columns, stat, curcmd);
+          stat &= ~stat_dirty;
+          continue;
+        }
+
       fakecmd:
         switch (kbd_state) {
         case kbd_result:
@@ -847,7 +869,6 @@ int main(int argc, char **argv)
     }
   }
 
-  if (tcsetattr(ttyfd, TCSANOW, &tty_saved) < 0)
-    panic("unable to restore TTY parameters");
+  ttyset(ttyfd, &tty_saved);
   return exit_status;
 }
-- 
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