fix: the characters that width is 2 will cost 2 cells, the characters…

README.md

@@ -37,18 +37,24 @@ package main
 import (
     "fmt"
     "github.com/chengxilo/virtualterm"
+    "log"
 )
 
 func main() {
     str := "hello\rvirtuaa\bl-terminal"
     vt := virtualterm.NewDefault()
     vt.Write([]byte(str))
     fmt.Println(str == "virtual-terminal")
-    fmt.Println(vt.String() == "virtual-terminal")
+    str,err := vt.String()
+    if err != nil {
+        log.Fatal(err)
+    }
+    fmt.Println(str == "virtual-terminal")
     // Output:
     // false
     // true
 }
+
 ```
 
 Use `virtualterm.Process` function. You will not need to create a virtual terminal and input on your own.

example/basic/main.go

@@ -3,14 +3,19 @@ package main
 import (
 	"fmt"
 	"github.com/chengxilo/virtualterm"
+	"log"
 )
 
 func main() {
 	str := "hello\rvirtuaa\bl-terminal"
 	vt := virtualterm.NewDefault()
 	vt.Write([]byte(str))
 	fmt.Println(str == "virtual-terminal")
-	fmt.Println(vt.String() == "virtual-terminal")
+	str, err := vt.String()
+	if err != nil {
+		log.Fatal(err)
+	}
+	fmt.Println(str == "virtual-terminal")
 	// Output:
 	// false
 	// true

go.mod

@@ -6,7 +6,9 @@ require github.com/stretchr/testify v1.9.0
 
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/mattn/go-runewidth v0.0.16 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/rivo/uniseg v0.2.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )
 

term.go

@@ -3,15 +3,19 @@ package virtualterm
 import (
 	"errors"
 	"fmt"
+	"github.com/mattn/go-runewidth"
 	"log"
 	"math"
 	"strconv"
 	"strings"
 )
 
-var INF = math.MaxInt - 1
 var ErrCannotHandle = errors.New("this csi is not supported or syntax error")
-var ErrNonDetermistics = errors.New("non-deterministic")
+
+// ErrNonDeterministic is created for some situation that cannot be handled well.
+// for example, if you write "你好\b啊" the result will be "你 啊" in Windows Powershell, and will be
+// "你好啊" in git bash in Windows. I would treat it as an error caused by users' input.
+var ErrNonDeterministic = errors.New("non-deterministic")
 
 // VirtualTerm this is created to simulate a terminal,handle the special character such as '\r','\b', "\033[1D".
 // For example: if you input "cute\rhat", the result of String() would be "hate"
@@ -23,9 +27,6 @@ type VirtualTerm struct {
 	// the content of virtual terminal
 	content [][]rune
 
-	// xOffset is the offset on X.
-	xOffset int
-
 	// silence will shut down the log.By default, it is true
 	silence bool
 }
@@ -162,62 +163,9 @@ func (vt *VirtualTerm) WriteString(s string) (n int, err error) {
 	return vt.Write([]byte(s))
 }
 
-// runeWidth
-func (*VirtualTerm) runeWidth(r rune) int {
-	if len(string(r)) >= 3 {
-		return 2
-	} else {
-		return 1
-	}
-}
-
 // cursorMove can control the cursor
 func (vt *VirtualTerm) cursorMove(x int, y int) {
-	// handle the offset first
-	if vt.xOffset != 0 {
-		x += vt.xOffset
-		vt.xOffset = 0
-	}
-	if x < 0 {
-		// move the cursor left
-		// this may cause offset
-		x = -x
-		var far int
-		for vt.cx > 0 && x > 0 {
-			far = vt.runeWidth(vt.content[vt.cy][vt.cx-1])
-			if x >= far {
-				x -= far
-				vt.cx--
-			} else {
-				break
-			}
-		}
-		if x == 1 && vt.cx != 0 {
-			vt.xOffset = -1
-		}
-	} else if x > 0 {
-		// move the cursor right
-		// this situation will not cause offset
-		for x > 0 {
-			// if cx is out of bound, add empty element
-			if vt.cx >= len(vt.content[vt.cy])-1 {
-				vt.content[vt.cy] = append(vt.content[vt.cy], ' ')
-			}
-			far := vt.runeWidth(vt.content[vt.cy][vt.cx])
-			if far <= x {
-				x -= far
-				vt.cx++
-			} else {
-				break
-			}
-		}
-		if x == 1 {
-			vt.xOffset = -1
-			vt.cx++
-		}
-	}
-
-	// avoid index out of bound
+	vt.cx = max(vt.cx+x, 0)
 	vt.cy = max(vt.cy+y, 0)
 	for vt.cy >= len(vt.content) {
 		vt.content = append(vt.content, []rune{' '})
@@ -231,22 +179,18 @@ func (vt *VirtualTerm) cursorMove(x int, y int) {
 func (vt *VirtualTerm) cursorHome() {
 	vt.cx = 0
 	vt.cy = 0
-	vt.xOffset = 0
 }
 
 // writeRune write Rune to content.
 func (vt *VirtualTerm) writeRune(r rune) error {
-	// if the offset of cursor is not zero, means that there will be non-deterministic for the output
-	// For example, if your output is "你好\bCOOL", than it might be "你好OOL"(git bash in Windows) or 你 COOL("Windows powershell")
-	// So it should be treated as an error.
-	if vt.xOffset != 0 {
-		return ErrNonDetermistics
+	wid := runewidth.RuneWidth(r)
+	// write according to the width of rune.
+	// For example: '中' need two cells, but 'a' only need one cell
+	for wid > 0 {
+		vt.content[vt.cy][vt.cx] = r
+		vt.cursorMove(1, 0)
+		wid--
 	}
-	// get the width of rune
-	far := vt.runeWidth(r)
-	vt.content[vt.cy][vt.cx] = r
-	vt.cursorMove(far, 0)
-
 	return nil
 }
 
@@ -256,11 +200,11 @@ func (vt *VirtualTerm) WriteRunes(p []rune) (n int, err error) {
 		switch p[i] {
 		case '\r':
 			// Carriage Return
-			vt.cursorMove(-INF, 0)
+			vt.cursorMove(-math.MaxInt, 0)
 		case '\n':
 			// NewLine
 			// If the cursor is on the last line, add a new line
-			vt.cursorMove(-INF, 1)
+			vt.cursorMove(-math.MaxInt, 1)
 		case '\b':
 			vt.cursorMove(-1, 0)
 		case '\033':
@@ -292,26 +236,44 @@ func (vt *VirtualTerm) WriteRunes(p []rune) (n int, err error) {
 }
 
 // writeString write String to content
-func (vt *VirtualTerm) writeString(s string) {
+func (vt *VirtualTerm) writeString(s string) error {
 	for _, c := range s {
-		vt.writeRune(c)
+		if err := vt.writeRune(c); err != nil {
+			return err
+		}
 	}
+	return nil
 }
 
-func (vt *VirtualTerm) String() string {
+// String get the result of the prediction.
+// If there is some non-deterministic,you will get an error.
+func (vt *VirtualTerm) String() (string, error) {
 	builder := strings.Builder{}
-	for i, line := range vt.content {
-		for j, c := range line {
-			if j == len(line)-1 {
+	for i := 0; i < len(vt.content); i++ {
+		for j := 0; j < len(vt.content[i]); j++ {
+			if j == len(vt.content[i])-1 {
 				break
 			}
-			builder.WriteRune(c)
+			c := vt.content[i][j]
+			wid := runewidth.RuneWidth(c)
+			// if it is a character cost 2 cells,such as '中','ひ','안',or emoji
+			if wid == 1 {
+				// append the character to result
+				builder.WriteRune(c)
+			} else if wid == 2 {
+				if vt.content[i][j] != vt.content[i][j+1] {
+					return "", ErrNonDeterministic
+				}
+				builder.WriteRune(c)
+				j++
+			}
+
 		}
 		if i != len(vt.content)-1 {
 			builder.WriteRune('\n')
 		}
 	}
-	return builder.String()
+	return builder.String(), nil
 }
 
 // Clear all the content in virtual terminal
@@ -334,5 +296,5 @@ func Process(input string) (string, error) {
 	if err != nil {
 		return "", err
 	}
-	return vt.String(), err
+	return vt.String()
 }

test/term_test.go

@@ -51,7 +51,7 @@ func TestCarriageReturn(t *testing.T) {
 		if err != nil {
 			t.Fatal(err)
 		}
-		actual := vt.String()
+		actual, _ := vt.String()
 		assert.Equal(t, te.output, actual)
 		vt.Clear()
 	}
@@ -74,7 +74,7 @@ func TestNewLine(t *testing.T) {
 		if err != nil {
 			t.Fatal(err)
 		}
-		actual := vt.String()
+		actual, _ := vt.String()
 		assert.Equal(t, te.output, actual)
 		vt.Clear()
 	}
@@ -95,7 +95,7 @@ func TestBackspace(t *testing.T) {
 		if err != nil {
 			t.Fatal(err)
 		}
-		actual := vt.String()
+		actual, _ := vt.String()
 		assert.Equal(t, te.output, actual)
 		vt.Clear()
 	}
@@ -107,6 +107,7 @@ func TestCSI(t *testing.T) {
 		input    string
 		expected string
 	}{
+		{"123\r嗨", "嗨3"},
 		{"\033[123*", ""},
 		{"你好\r\033[4C啊", "你好啊"},
 		{"你好\r\033[C", "你好"},
@@ -136,7 +137,7 @@ func TestCSI(t *testing.T) {
 		if err != nil {
 			t.Fatal(err, i)
 		}
-		actual := vt.String()
+		actual, _ := vt.String()
 		if actual != te.expected {
 			log.Print("actual: "+actual+"expected: ", te.expected, "test index: ", i)
 			t.Fail()
@@ -150,17 +151,18 @@ func TestInvalidInput(t *testing.T) {
 	tests := []struct {
 		input string
 	}{
+		{"你好\ba"},
 		{"我是\b猫"},
 		{"我是\033[1D猫"},
 		{"我是\bhero"},
 		{"锄禾日\b\033当[1C午"},
 		{"\bレ\033[Dモン"},
 	}
 	for _, te := range tests {
-		_, err := vt.WriteString(te.input)
-		if !errors.Is(err, virtualterm.ErrNonDetermistics) {
-			t.Logf("error is not expected")
-			t.Fail()
+		vt.WriteString(te.input)
+		if _, err := vt.String(); !errors.Is(err, virtualterm.ErrNonDeterministic) {
+			t.Fatal(err)
 		}
+		vt.Clear()
 	}
 }