fix(readline): take into account character width (#145)

first step towards unicode support yay

go.mod

@@ -20,6 +20,7 @@ require (
 	github.com/rivo/uniseg v0.2.0 // indirect
 	golang.org/x/sync v0.0.0-20210220032951-036812b2e83c // indirect
 	golang.org/x/sys v0.0.0-20220227234510-4e6760a101f9 // indirect
+	golang.org/x/text v0.3.6 // indirect
 )
 
 replace mvdan.cc/sh/v3 => github.com/Rosettea/sh/v3 v3.4.0-0.dev.0.20220306140409-795a84b00b4e

go.sum

@@ -1,5 +1,3 @@
-github.com/Rosettea/golua v0.0.0-20220406024702-f447a8095170 h1:k2MAUwR1diHqqoFPEhxMKAQoz131tMSti8ArzCTg2HI=
-github.com/Rosettea/golua v0.0.0-20220406024702-f447a8095170/go.mod h1:9jzpYPiU2is0HVGCiuIOBSXdergHUW44IEjmuN1UrIE=
 github.com/Rosettea/golua v0.0.0-20220419183026-6d22d6fec5ac h1:dtXrgjch8PQyf7C90anZUquB5U3dr8AcMGJofeuirrI=
 github.com/Rosettea/golua v0.0.0-20220419183026-6d22d6fec5ac/go.mod h1:9jzpYPiU2is0HVGCiuIOBSXdergHUW44IEjmuN1UrIE=
 github.com/Rosettea/sh/v3 v3.4.0-0.dev.0.20220306140409-795a84b00b4e h1:P2XupP8SaylWaudD1DqbWtZ3mIa8OsE9635LmR+Q+lg=
@@ -57,6 +55,7 @@ golang.org/x/term v0.0.0-20210916214954-140adaaadfaf/go.mod h1:jbD1KX2456YbFQfuX
 golang.org/x/term v0.0.0-20210927222741-03fcf44c2211 h1:JGgROgKl9N8DuW20oFS5gxc+lE67/N3FcwmBPMe7ArY=
 golang.org/x/term v0.0.0-20210927222741-03fcf44c2211/go.mod h1:jbD1KX2456YbFQfuXm/mYQcufACuNUgVhRMnK/tPxf8=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
+golang.org/x/text v0.3.6 h1:aRYxNxv6iGQlyVaZmk6ZgYEDa+Jg18DxebPSrd6bg1M=
 golang.org/x/text v0.3.6/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=

readline/update.go

@@ -1,5 +1,7 @@
 package readline
 
+import "golang.org/x/text/width"
+
 // updateHelpers is a key part of the whole refresh process:
 // it should coordinate reprinting the input line, any Infos and completions
 // and manage to get back to the current (computed) cursor coordinates
@@ -21,6 +23,23 @@ func (rl *Instance) updateHelpers() {
 	rl.renderHelpers()
 }
 
+const tabWidth = 4
+
+func getWidth(x []rune) int {
+	var w int
+	for _, j := range x {
+		k := width.LookupRune(j).Kind()
+		if j == '\t' {
+			w += tabWidth
+		} else if k == width.EastAsianWide || k == width.EastAsianFullwidth {
+			w += 2
+		} else {
+			w++
+		}
+	}
+	return w
+}
+
 // Update reference should be called only once in a "loop" (not Readline(), but key control loop)
 func (rl *Instance) updateReferences() {
 
@@ -33,11 +52,11 @@ func (rl *Instance) updateReferences() {
 
 	var fullLine, cPosLine int
 	if len(rl.currentComp) > 0 {
-		fullLine = len(rl.lineComp)
+		fullLine = getWidth(rl.lineComp)
-		cPosLine = len(rl.lineComp[:rl.pos])
+		cPosLine = getWidth(rl.lineComp[:rl.pos])
 	} else {
-		fullLine = len(rl.line)
+		fullLine = getWidth(rl.line)
-		cPosLine = len(rl.line[:rl.pos])
+		cPosLine = getWidth(rl.line[:rl.pos])
 	}
 
 	// We need the X offset of the whole line
@@ -106,7 +125,7 @@ func (rl *Instance) clearHelpers() {
 // and replaces the cursor to its current position. This function never
 // computes or refreshes any value, except from inside the echo function.
 func (rl *Instance) renderHelpers() {
-	
+
 	// when the instance is in this state we want it to be "below" the user's
 	// input for it to be aligned properly
 	if !rl.compConfirmWait {