diff --git a/complete.go b/complete.go
index 6d5bc16..3a7aa4f 100644
--- a/complete.go
+++ b/complete.go
@@ -183,7 +183,7 @@ func (o *opCompleter) CompleteRefresh() {
 			colWidth = w
 		}
 	}
-	colNum := getWidth(o.op.cfg.StdoutFd) / (colWidth + o.candidateOff + 2)
+	colNum := o.op.cfg.FuncGetWidth() / (colWidth + o.candidateOff + 2)
 	o.candidateColNum = colNum
 	buf := bytes.NewBuffer(nil)
 	buf.Write(bytes.Repeat([]byte("\n"), lineCnt))
diff --git a/operation.go b/operation.go
index 02cc2e3..e1e8b07 100644
--- a/operation.go
+++ b/operation.go
@@ -2,10 +2,7 @@ package readline
 
 import (
 	"errors"
-	"fmt"
 	"io"
-
-	"golang.org/x/crypto/ssh/terminal"
 )
 
 var (
@@ -58,7 +55,7 @@ func (w *wrapWriter) Write(b []byte) (int, error) {
 func NewOperation(t *Terminal, cfg *Config) *Operation {
 	op := &Operation{
 		t:       t,
-		buf:     NewRuneBuffer(t, cfg.Prompt, cfg.MaskRune, cfg),
+		buf:     NewRuneBuffer(t, cfg.Prompt, cfg),
 		outchan: make(chan []rune),
 		errchan: make(chan error),
 	}
@@ -341,16 +338,7 @@ func (o *Operation) PasswordWithConfig(cfg *Config) ([]byte, error) {
 }
 
 func (o *Operation) Password(prompt string) ([]byte, error) {
-	w := o.Stdout()
-	if prompt != "" {
-		fmt.Fprintf(w, prompt)
-	}
-	o.t.EnterRawMode()
-	defer o.t.ExitRawMode()
-
-	b, err := terminal.ReadPassword(int(o.cfg.Stdin.Fd()))
-	fmt.Fprint(w, "\r\n")
-	return b, err
+	return o.PasswordEx(prompt, nil)
 }
 
 func (o *Operation) SetTitle(t string) {
diff --git a/password.go b/password.go
index 95a939a..4b07379 100644
--- a/password.go
+++ b/password.go
@@ -21,7 +21,7 @@ func (o *opPassword) EnterPasswordMode(cfg *Config) (err error) {
 
 func (o *opPassword) PasswordConfig() *Config {
 	return &Config{
-		MaskRune:        '*',
+		EnableMask:      true,
 		InterruptPrompt: "\n",
 		EOFPrompt:       "\n",
 		HistoryLimit:    -1,
diff --git a/readline.go b/readline.go
index 0ffc5b4..53755fc 100644
--- a/readline.go
+++ b/readline.go
@@ -11,11 +11,6 @@ type Instance struct {
 	Operation *Operation
 }
 
-type FdReader interface {
-	io.Reader
-	Fd() uintptr
-}
-
 type Config struct {
 	// prompt supports ANSI escape sequence, so we can color some characters even in windows
 	Prompt string
@@ -39,12 +34,17 @@ type Config struct {
 	InterruptPrompt string
 	EOFPrompt       string
 
-	Stdin  FdReader
+	FuncGetWidth func() int
+
+	Stdin  io.Reader
 	Stdout io.Writer
 	Stderr io.Writer
 
-	MaskRune rune
+	EnableMask bool
+	MaskRune   rune
 
+	// erase the editing line after user submited it
+	// it often use in IM.
 	UniqueEditLine bool
 
 	// force use interactive even stdout is not a tty
@@ -100,6 +100,10 @@ func (c *Config) Init() error {
 		c.EOFPrompt = ""
 	}
 
+	if c.FuncGetWidth == nil {
+		c.FuncGetWidth = genGetWidthFunc(c.StdoutFd)
+	}
+
 	return nil
 }
 
diff --git a/runebuf.go b/runebuf.go
index bf4c222..a137fb9 100644
--- a/runebuf.go
+++ b/runebuf.go
@@ -18,7 +18,6 @@ type RuneBuffer struct {
 	idx    int
 	prompt []rune
 	w      io.Writer
-	mask   rune
 
 	cleanInScreen bool
 	interactive   bool
@@ -41,10 +40,9 @@ func (r *RuneBuffer) Restore() {
 	})
 }
 
-func NewRuneBuffer(w io.Writer, prompt string, mask rune, cfg *Config) *RuneBuffer {
+func NewRuneBuffer(w io.Writer, prompt string, cfg *Config) *RuneBuffer {
 	rb := &RuneBuffer{
 		w:           w,
-		mask:        mask,
 		interactive: cfg.useInteractive(),
 		cfg:         cfg,
 	}
@@ -58,7 +56,7 @@ func (r *RuneBuffer) SetConfig(cfg *Config) {
 }
 
 func (r *RuneBuffer) SetMask(m rune) {
-	r.mask = m
+	r.cfg.MaskRune = m
 }
 
 func (r *RuneBuffer) CurrentWidth(x int) int {
@@ -295,7 +293,7 @@ func (r *RuneBuffer) MoveToLineEnd() {
 }
 
 func (r *RuneBuffer) LineCount() int {
-	return LineCount(r.cfg.StdoutFd, runes.WidthAll(r.buf)+r.PromptLen())
+	return LineCount(r.cfg.FuncGetWidth, runes.WidthAll(r.buf)+r.PromptLen())
 }
 
 func (r *RuneBuffer) MoveTo(ch rune, prevChar, reverse bool) (success bool) {
@@ -329,7 +327,7 @@ func (r *RuneBuffer) MoveTo(ch rune, prevChar, reverse bool) (success bool) {
 
 func (r *RuneBuffer) IdxLine() int {
 	totalWidth := runes.WidthAll(r.buf[:r.idx]) + r.PromptLen()
-	w := getWidth(r.cfg.StdoutFd)
+	w := r.cfg.FuncGetWidth()
 	if w <= 0 {
 		return -1
 	}
@@ -368,12 +366,12 @@ func (r *RuneBuffer) Refresh(f func()) {
 func (r *RuneBuffer) output() []byte {
 	buf := bytes.NewBuffer(nil)
 	buf.WriteString(string(r.prompt))
-	if r.mask != 0 && len(r.buf) > 0 {
-		buf.Write([]byte(strings.Repeat(string(r.mask), len(r.buf)-1)))
+	if r.cfg.EnableMask && len(r.buf) > 0 {
+		buf.Write([]byte(strings.Repeat(string(r.cfg.MaskRune), len(r.buf)-1)))
 		if r.buf[len(r.buf)-1] == '\n' {
 			buf.Write([]byte{'\n'})
 		} else {
-			buf.Write([]byte(string(r.mask)))
+			buf.Write([]byte(string(r.cfg.MaskRune)))
 		}
 	} else {
 		buf.Write([]byte(string(r.buf)))
diff --git a/search.go b/search.go
index fdcab37..3b40ad6 100644
--- a/search.go
+++ b/search.go
@@ -125,7 +125,7 @@ func (o *opSearch) SearchRefresh(x int) {
 	}
 	x = o.buf.CurrentWidth(x)
 	x += o.buf.PromptLen()
-	x = x % getWidth(o.cfg.StdoutFd)
+	x = x % o.cfg.FuncGetWidth()
 
 	if o.markStart > 0 {
 		o.buf.SetStyle(o.markStart, o.markEnd, "4")
diff --git a/std.go b/std.go
index 326e64b..5fe2c29 100644
--- a/std.go
+++ b/std.go
@@ -17,6 +17,7 @@ var (
 	stdOnce sync.Once
 )
 
+// global instance will not submit history automatic
 func getInstance() *Instance {
 	stdOnce.Do(func() {
 		std, _ = NewEx(&Config{
@@ -26,6 +27,10 @@ func getInstance() *Instance {
 	return std
 }
 
+// let readline load history from filepath
+// and try to persist history into disk
+// set fp to "" to prevent readline persisting history to disk
+// so the `AddHistory` will return nil error forever.
 func SetHistoryPath(fp string) {
 	ins := getInstance()
 	cfg := ins.Config.Clone()
@@ -33,6 +38,7 @@ func SetHistoryPath(fp string) {
 	ins.SetConfig(cfg)
 }
 
+// set auto completer to global instance
 func SetAutoComplete(completer AutoCompleter) {
 	ins := getInstance()
 	cfg := ins.Config.Clone()
@@ -40,11 +46,14 @@ func SetAutoComplete(completer AutoCompleter) {
 	ins.SetConfig(cfg)
 }
 
+// add history to global instance manually
+// raise error only if `SetHistoryPath` is set with a non-empty path
 func AddHistory(content string) error {
 	ins := getInstance()
 	return ins.SaveHistory(content)
 }
 
+// readline with global configs
 func Line(prompt string) (string, error) {
 	ins := getInstance()
 	ins.SetPrompt(prompt)
diff --git a/terminal.go b/terminal.go
index 71a72f6..b65361c 100644
--- a/terminal.go
+++ b/terminal.go
@@ -36,7 +36,7 @@ func NewTerminal(cfg *Config) (*Terminal, error) {
 }
 
 func (t *Terminal) EnterRawMode() (err error) {
-	t.state, err = MakeRaw(int(t.cfg.Stdin.Fd()))
+	t.state, err = MakeRaw(int(t.cfg.StdinFd))
 	return err
 }
 
@@ -44,7 +44,7 @@ func (t *Terminal) ExitRawMode() (err error) {
 	if t.state == nil {
 		return
 	}
-	err = Restore(int(t.cfg.Stdin.Fd()), t.state)
+	err = Restore(int(t.cfg.StdinFd), t.state)
 	if err == nil {
 		t.state = nil
 	}
diff --git a/utils.go b/utils.go
index 6be2e38..a270952 100644
--- a/utils.go
+++ b/utils.go
@@ -87,8 +87,8 @@ func escapeKey(r rune) rune {
 }
 
 // calculate how many lines for N character
-func LineCount(stdoutFd int, w int) int {
-	screenWidth := getWidth(stdoutFd)
+func LineCount(getWidth func() int, w int) int {
+	screenWidth := getWidth()
 	r := w / screenWidth
 	if w%screenWidth != 0 {
 		r++
@@ -116,3 +116,9 @@ func GetInt(s []string, def int) int {
 	}
 	return c
 }
+
+func genGetWidthFunc(fd int) func() int {
+	return func() int {
+		return getWidth(fd)
+	}
+}