From b765e587bf737efffbfe4fff087452de7a090708 Mon Sep 17 00:00:00 2001

From: Jim Warner <james.warner@comcast.net>

Date: Fri, 28 Jun 2013 00:00:00 -0500

Subject: [PATCH] top: enable screen contents preservation at end-of-job

The title of this commit is actually quite misleading.

Were it more accurate, it would at least mention a tty

emulator's scrollback buffer, which was the cumulation

of a long pursuit to reduce the SIGWINCH overhead when

a window manager carelessly floods an application with

that signal *while* a user is still resizing a window!

Disabling and enabling that scrollback buffer resulted

in the final top display replaced with original screen

contents, a phenomenon acknowledged at the time but it

also represented a user interface change which has now

produced the first request for return to old behavior.

After the SIGWINCH dust settled, another problem arose

regarding behaviors under the 'screen' window manager.

In response, top was refactored a bit to avoid display

corruption. That was before discovering 'screen' could

duplicate the scrollback buffer behavior top expected.

As it turns out, the 'screen' refactoring had probably

made scrollback buffer manipulation unnecessary. Still

one could argue that a window should not be allowed to

scroll while a constantly updating program was active.

The solution represented in this commit returns former

behavior at program end (retaining top's last screen).

And if we ever wish to disable scrollback buffers, the

associated logic was retained but made conditional. It

is not reflected in configure.ac but might be someday.

Lastly, this commit corrects cursor positioning when a

^C is issued under 'Fields Management' at any terminal

that didn't have a scrollback buffer (i.e. a console).

Reference(s):

https://bugzilla.redhat.com/show_bug.cgi?id=977561

http://www.freelists.org/post/procps/top-library-miscellaneous-tweaks,1

. screen program refactor

commit 0fe393ff270922cd4f6edbcaabba006314e73a37

. scrollback buffer disabled

commit dedaf6e1a81738ff08ee8e8523871e12f555ad6d

. sigwinch management defines

commit adca737758e5afc7be344a736953931894cbc19f

commit 4f33b6b8c56464b4044deb29a3bb0e32622e108f

Signed-off-by: Jim Warner <james.warner@comcast.net>

---

 top/top.c | 18 +++++++++++-------

 top/top.h |  1 +

 2 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/top/top.c b/top/top.c

index 1d38c0f..cdcf3c0 100644

--- a/top/top.c

+++ b/top/top.c

@@ -72,8 +72,9 @@ static struct termios Tty_original,    // our inherited terminal definition

                       Tty_raw;         // for unsolicited input

 static int Ttychanged = 0;

-        /* Last established cursor state/shape */

+        /* Last established cursor state/shape, and is re-position needed */

 static const char *Cursor_state = "";

+static int         Cursor_repos;

         /* Program name used in error messages and local 'rc' file name */

 static char *Myname;

@@ -350,12 +351,15 @@ static void at_eoj (void) {

    if (Ttychanged) {

       tcsetattr(STDIN_FILENO, TCSAFLUSH, &Tty_original);

       if (keypad_local) putp(keypad_local);

+      if (Cursor_repos) putp(tg2(0, Screen_rows));

       putp("\n");

+#ifdef OFF_SCROLLBK

       if (exit_ca_mode) {

          // this next will also replace top's most recent screen with the

          // original display contents that were visible at our invocation

          putp(exit_ca_mode);

       }

+#endif

       putp(Cap_curs_norm);

       putp(Cap_clr_eol);

 #ifndef RMAN_IGNORED

@@ -591,17 +595,13 @@ static void sig_endpgm (int dont_care_sig) {

         /*

          * Catches:

-         *    SIGTSTP, SIGTTIN and SIGTTOU

-         * note:

-         *    we don't fiddle with with those enter/exit_ca_mode strings

-         *    because we want to retain most of the last screen contents

-         *    as a visual reminder this program is suspended, not ended! */

+         *    SIGTSTP, SIGTTIN and SIGTTOU */

 static void sig_paused (int dont_care_sig) {

 // POSIX.1-2004 async-signal-safe: tcsetattr, tcdrain, raise

    if (-1 == tcsetattr(STDIN_FILENO, TCSAFLUSH, &Tty_original))

       error_exit(fmtmk(N_fmt(FAIL_tty_set_fmt), strerror(errno)));

    if (keypad_local) putp(keypad_local);

-   putp(tg2(0, Screen_rows));

+   if (Cursor_repos) putp(tg2(0, Screen_rows));

    putp(Cap_curs_norm);

 #ifndef RMAN_IGNORED

    putp(Cap_smam);

@@ -2120,6 +2120,7 @@ static void fields_utility (void) {

    int i, key;

    FLG_t f;

+   Cursor_repos = 1;

    spewFI

 signify_that:

    putp(Cap_clr_scr);

@@ -2180,6 +2181,7 @@ signify_that:

             break;

       }

    } while (key != 'q' && key != kbd_ESC);

+   Cursor_repos = 0;

  #undef unSCRL

  #undef swapEM

  #undef spewFI

@@ -3768,8 +3770,10 @@ static void whack_terminal (void) {

    // thanks anyway stdio, but we'll manage buffering at the frame level...

    setbuffer(stdout, Stdout_buf, sizeof(Stdout_buf));

 #endif

+#ifdef OFF_SCROLLBK

    // this has the effect of disabling any troublesome scrollback buffer...

    if (enter_ca_mode) putp(enter_ca_mode);

+#endif

    // and don't forget to ask iokey to initialize his tinfo_tab

    iokey(0);

 } // end: whack_terminal

diff --git a/top/top.h b/top/top.h

index f356798..a8a7357 100644

--- a/top/top.h

+++ b/top/top.h

@@ -41,6 +41,7 @@

 //#define INSP_SAVEBUF            /* preserve 'Insp_buf' contents in a file  */

 //#define INSP_SLIDE_1            /* when scrolling left/right don't move 8  */

 //#define OFF_HST_HASH            /* use BOTH qsort+bsrch vs. hashing scheme */

+//#define OFF_SCROLLBK            /* disable tty emulators scrollback buffer */

 //#define OFF_STDIOLBF            /* disable our own stdout _IOFBF override  */

 //#define PRETEND2_5_X            /* pretend we're linux 2.5.x (for IO-wait) */

 //#define PRETEND8CPUS            /* pretend we're smp with 8 ticsers (sic)  */

-- 

1.8.1.2