Checking line index before attempting purge. Fixes #891

flex.go

@@ -4,12 +4,16 @@ import (
 	"github.com/gdamore/tcell/v2"
 )
 
-// Configuration values.
+// Flex directions.
 const (
-	FlexRow       = 0 // One item per row.
-	FlexColumn    = 1 // One item per column.
-	FlexRowCSS    = 1 // As defined in CSS, items distributed along a row.
-	FlexColumnCSS = 0 // As defined in CSS, items distributed within a column.
+	// One item per row.
+	FlexRow = 0
+	// One item per column.
+	FlexColumn = 1
+	// As defined in CSS, items distributed along a row.
+	FlexRowCSS = 1
+	// As defined in CSS, items distributed within a column.
+	FlexColumnCSS = 0
 )
 
 // flexItem holds layout options for one item.
@@ -49,7 +53,7 @@ type Flex struct {
 // background before any items are drawn, set it to a box with the desired
 // color:
 //
-//   flex.Box = NewBox()
+//	flex.Box = NewBox()
 func NewFlex() *Flex {
 	f := &Flex{
 		direction: FlexColumn,

textview.go

@@ -1259,7 +1259,7 @@ func (t *TextView) Draw(screen tcell.Screen) {
 	}
 
 	// Purge.
-	if purgeStart > 0 {
+	if purgeStart > 0 && purgeStart < len(t.lineIndex) {
 		newText := t.text.String()[t.lineIndex[purgeStart].offset:]
 		t.text.Reset()
 		t.text.WriteString(newText)