Fix scrolling with wrapped lines

README.md

@@ -21,15 +21,20 @@ package main
 import (
 	"fmt"
 	"github.com/elk-language/go-prompt"
+	pstrings "github.com/elk-language/go-prompt/strings"
 )
 
-func completer(d prompt.Document) []prompt.Suggest {
+func completer(d prompt.Document) ([]prompt.Suggest, pstrings.RuneNumber, pstrings.RuneNumber) {
+	endIndex := d.CurrentRuneIndex()
+	w := d.GetWordBeforeCursor()
+	startIndex := endIndex - pstrings.RuneCount(w)
+
 	s := []prompt.Suggest{
 		{Text: "users", Description: "Store the username and age"},
 		{Text: "articles", Description: "Store the article text posted by user"},
 		{Text: "comments", Description: "Store the text commented to articles"},
 	}
-	return prompt.FilterHasPrefix(s, d.GetWordBeforeCursor(), true)
+	return prompt.FilterHasPrefix(s, w, true), startIndex, endIndex
 }
 
 func main() {

buffer.go

@@ -179,6 +179,7 @@ func (b *Buffer) DeleteBeforeCursor(count istrings.RuneNumber, columns istrings.
 			cursorPosition: b.cursorPosition - istrings.RuneNumber(len([]rune(deleted))),
 		}, columns, rows)
 	}
+	b.RecalculateStartLine(columns, rows)
 	return
 }
 
@@ -205,6 +206,7 @@ func (b *Buffer) Delete(count istrings.RuneNumber, col istrings.Width, row int)
 		)
 
 		deleted := string(deletedRunes)
+		b.RecalculateStartLine(col, row)
 		return deleted
 	}
 

renderer.go

@@ -250,6 +250,7 @@ func (r *Renderer) renderText(lexer Lexer, input string, startLine int) {
 	for _, char := range input {
 		if lineCharIndex >= col || char == '\n' {
 			lineNumber++
+			lineCharIndex = 0
 			if lineNumber-1 < startLine {
 				continue
 			}
@@ -258,7 +259,6 @@ func (r *Renderer) renderText(lexer Lexer, input string, startLine int) {
 			}
 			lineBuffer.WriteRune('\n')
 			r.renderLine(prefix, lineBuffer.String(), r.inputTextColor)
-			lineCharIndex = 0
 			lineBuffer.Reset()
 			if char != '\n' {
 				lineBuffer.WriteRune(char)
@@ -271,11 +271,11 @@ func (r *Renderer) renderText(lexer Lexer, input string, startLine int) {
 			continue
 		}
 
+		lineCharIndex += istrings.GetRuneWidth(char)
 		if lineNumber < startLine {
 			continue
 		}
 		lineBuffer.WriteRune(char)
-		lineCharIndex += istrings.GetRuneWidth(char)
 	}
 
 	r.renderLine(prefix, lineBuffer.String(), r.inputTextColor)
@@ -376,6 +376,7 @@ tokenLoop:
 		for _, char := range text {
 			if lineCharIndex >= col || char == '\n' {
 				lineNumber++
+				lineCharIndex = 0
 				if lineNumber-1 < startLine {
 					continue charLoop
 				}
@@ -385,7 +386,6 @@ tokenLoop:
 				lineBuffer = append(lineBuffer, '\n')
 				r.writeColor(lineBuffer, token.Color())
 				r.renderPrefix(multilinePrefix)
-				lineCharIndex = 0
 				lineBuffer = lineBuffer[:0]
 				if char != '\n' {
 					size := utf8.EncodeRune(runeBuffer, char)
@@ -395,12 +395,12 @@ tokenLoop:
 				continue charLoop
 			}
 
+			lineCharIndex += istrings.GetRuneWidth(char)
 			if lineNumber < startLine {
 				continue charLoop
 			}
 			size := utf8.EncodeRune(runeBuffer, char)
 			lineBuffer = append(lineBuffer, runeBuffer[:size]...)
-			lineCharIndex += istrings.GetRuneWidth(char)
 		}
 		if len(lineBuffer) > 0 {
 			r.writeColor(lineBuffer, token.Color())