[Bug-readline] Command "clear-screen" should clear scrollback buffer (if supported) as well

[burning2007]

Version: 6.3-release
Machine: x86_64
OS: linux-gnu
Compiler: x86_64-solus-linux-gcc
Machine Type: x86_64-solus-linux-gnu

Description:

The command "clear-screen" should clear terminal's scrollback buffer as well. 
`clear` from ncurses does so. Seems like clearing scrollback along with screen 
is desired behavior in almost all cases. Another option is to provide 
"clear-screen-and-scrollback" command and let the user to pick what he like.

How to repeat:

Ensure that your terminal support `CSI ED 2` sequence (linux console, xterm, 
most of libvte-based terminals, including gnome-terminal, xfce-terminal): 
`infocmp -x |grep E3`. `cat` something that takes more than one screen, then 
(assuming that "clear-screen" bound as by default) press "C-l". Screen will be 
cleared, but you still have to be able to scroll back.

Fix:

Here is possible patch:

diff --git a/display.c b/display.c
index 41fb053..dc7a578 100644
--- a/display.c
+++ b/display.c
@@ -2668,8 +2668,13 @@ void
 _rl_clear_screen ()
 {
 #ifndef __DJGPP__
-  if (_rl_term_clrpag)
+  if (_rl_term_clrpag) {
     tputs (_rl_term_clrpag, 1, _rl_output_character_function);
+
+    if (_rl_term_clrscrollback) {
+      tputs (_rl_term_clrscrollback, 1, _rl_output_character_function);
+    }
+  }
   else
     rl_crlf ();
 #else
diff --git a/rlprivate.h b/rlprivate.h
index fc3856a..9dfd8b7 100644
--- a/rlprivate.h
+++ b/rlprivate.h
@@ -534,6 +534,7 @@ extern int _rl_enable_keypad;
 extern int _rl_enable_meta;
 extern char *_rl_term_clreol;
 extern char *_rl_term_clrpag;
+extern char *_rl_term_clrscrollback;
 extern char *_rl_term_im;
 extern char *_rl_term_ic;
 extern char *_rl_term_ei;
diff --git a/terminal.c b/terminal.c
index ef2884e..7bcde2c 100644
--- a/terminal.c
+++ b/terminal.c
@@ -112,6 +112,7 @@ char PC, *BC, *UP;
 /* Some strings to control terminal actions.  These are output by tputs (). */
 char *_rl_term_clreol;
 char *_rl_term_clrpag;
+char *_rl_term_clrscrollback;
 char *_rl_term_cr;
 char *_rl_term_backspace;
 char *_rl_term_goto;
@@ -393,6 +394,7 @@ static const struct _tc_string tc_strings[] =
   { "IC", &_rl_term_IC },
   { "ce", &_rl_term_clreol },
   { "cl", &_rl_term_clrpag },
+  { "E3", &_rl_term_clrscrollback },
   { "cr", &_rl_term_cr },
   { "dc", &_rl_term_dc },
   { "ei", &_rl_term_ei },
@@ -445,7 +447,7 @@ _rl_init_terminal_io (terminal_name)
   int tty, tgetent_ret;

   term = terminal_name ? terminal_name : sh_get_env_value ("TERM");
-  _rl_term_clrpag = _rl_term_cr = _rl_term_clreol = (char *)NULL;
+  _rl_term_clrpag = _rl_term_cr = _rl_term_clreol = _rl_term_clrscrollback = 
(char *)NULL;
   tty = rl_instream ? fileno (rl_instream) : 0;

   if (term == 0)
@@ -458,7 +460,7 @@ _rl_init_terminal_io (terminal_name)
   _rl_term_mm = _rl_term_mo = (char *)NULL;
   _rl_terminal_can_insert = term_has_meta = _rl_term_autowrap = 0;
   _rl_term_cr = "\r";
-  _rl_term_clreol = _rl_term_clrpag = _rl_term_backspace = (char *)NULL;
+  _rl_term_clreol = _rl_term_clrpag = _rl_term_backspace = 
_rl_term_clrscrollback = (char *)NULL;
   _rl_term_goto = _rl_term_pc = _rl_term_ip = (char *)NULL;
   _rl_term_ks = _rl_term_ke =_rl_term_vs = _rl_term_ve = (char *)NULL;
   _rl_term_kh = _rl_term_kH = _rl_term_at7 = _rl_term_kI = (char *)NULL;