From e27f247a3ec72dc2594d367db0e0ee31068c64eb Mon Sep 17 00:00:00 2001
From: Niels Widger <niels@qacafe.com>
Date: Fri, 10 Feb 2017 08:16:11 -0500
Subject: [PATCH] Support zero parameteter 'CSI n m' in parseOne

According to https://en.wikipedia.org/wiki/ANSI_escape_code#CSI_codes,
a zero-parameter 'CSI n m' code (for setting SGR parameters) should be
treated as the same as 'CSI 0 m'.  This PR changes
escapeInterpreter.parseOne to support this shorthand.
---
 escape.go | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/escape.go b/escape.go
index 008330e..c3ea31a 100644
--- a/escape.go
+++ b/escape.go
@@ -28,7 +28,6 @@ const (
 
 var (
 	errNotCSI        = errors.New("Not a CSI escape sequence")
-	errCSINotANumber = errors.New("CSI escape sequence was expecting a number or a ;")
 	errCSIParseError = errors.New("CSI escape sequence parsing error")
 	errCSITooLong    = errors.New("CSI escape sequence is too long")
 )
@@ -99,12 +98,16 @@ func (ei *escapeInterpreter) parseOne(ch rune) (isEscape bool, err error) {
 		}
 		return false, errNotCSI
 	case stateCSI:
-		if ch >= '0' && ch <= '9' {
-			ei.state = stateParams
-			ei.csiParam = append(ei.csiParam, string(ch))
-			return true, nil
+		switch {
+		case ch >= '0' && ch <= '9':
+			ei.csiParam = append(ei.csiParam, "")
+		case ch == 'm':
+			ei.csiParam = append(ei.csiParam, "0")
+		default:
+			return false, errCSIParseError
 		}
-		return false, errCSINotANumber
+		ei.state = stateParams
+		fallthrough
 	case stateParams:
 		switch {
 		case ch >= '0' && ch <= '9':