[mpg123-devel] [PATCH] term_posix: Ignore escape sequences

[Peter T. <pe...@ti...>]

I have an issue with occasionally hitting the wrong special key while 
using mpg123 in terminal control mode, and depending on the exact 
terminal code the terminal emulator sends for that key, it tends to 
have an undesirable effect on the state of the player. Mpg123 already 
ignores other keys it doesn't recognize, but I wanted it to ignore 
complete escape sequences as well.

I did a brief survey of special keys in the terminal emulators I have 
easy access to, and I think all these escape sequences can be ignored 
by discarding the leading escape character(s), then any occurrences of 
the characters `[0123456789;O`, followed by a character not in that 
list.

                Kitty           urxvt           Linux console
F1              \eOP            \e[11~          \e[[A
Shift-F1        \e[1;2P         \e[23~          \e[25~
Ctrl-F1         \e[1;5P         \e[11^
Alt-F1          \e[1;3P         \e\e[11~
F2              \eOQ            \e[12~          \e[[B
F3              \eOR            \e[13~          \e[[C
F4              \eOS            \e[14~          \e[[D
F5              \e[15~          \e[15~          \e[[E
F6              \e[17~          \e[17~          \e[17~
F7              \e[18~          \e[18~          \e[18~
F8              \e[19~          \e[19~          \e[19~
F9              \e[20~          \e[20~          \e[20~
F10             \e[21~          \e[21~          \e[21~
F11             \e[23~          \e[23~          \e[23~
F12             \e[24~          \e[24~          \e[24~
Shift-F12       \e[24;2~        \e[24$
Ctrl-F12        \e[24;5~        \e[24^
Alt-F12         \e[24;3~        \e\e[24~
Home            \e[H            \e[7~           \e[1~
End             \e[F            \e[8~           \e[4~
Insert          \e[2~           \e[2~           \e[2~
Delete          \e[3~           \e[3~           \e[3~
PgUp            \e[5~           \e[5~           \e[5~
PgDn            \e[6~           \e[6~           \e[6~
Up              \e[A            \e[A            \e[A
Down            \e[B            \e[B            \e[B
Left            \e[D            \e[D            \e[D
Right           \e[C            \e[C            \e[C
Kp5             \e[E            \e[G
Super-PrtSc     \e[57361;9u

I've applied the patch below to my copy of mpg123 and it works for me. 
I thought I'd share it upstream in case anyone else finds it useful.


Index: src/term_posix.c
===================================================================
--- src/term_posix.c	(revision 5528)
+++ src/term_posix.c	(working copy)
@@ -196,6 +196,7 @@
 #else
 	fd_set r;
 	struct timeval t;
+	static int in_escape_seq = 0;

 	/* Shortcut: If some other means sent a key, use it. */
 	if(prekey)
@@ -215,9 +216,23 @@
 	if(select(term_fd+1,&r,NULL,NULL,(stopped) ? NULL : &t) > 0 && FD_ISSET(term_fd,&r))
 	{
 		if(read(term_fd,val,1) <= 0)
-		return 0; /* Well, we couldn't read the key, so there is none. */
+			return 0; /* Well, we couldn't read the key, so there is none. */
+		if(*val == '\x1b')
+		{
+			/* Ignore escape sequences. */
+			in_escape_seq = 1;
+			return 0;
+		}
+		if(in_escape_seq)
+		{
+			/* Any of the following characters continue the escape sequence. Anything
+			   else terminates it. In either case, ignore the current character. */
+			if(!strchr("[0123456789;O", *val))
+				in_escape_seq = 0;
+			return 0;
+		}
 		else
-		return 1;
+			return 1;
 	}
 #endif
 	else return 0;

-- 
Peter Tirsek