From 5c84cf7e90211fa12eab08590c79a3d64daedbe9 Mon Sep 17 00:00:00 2001
From: Chris Waldon <christopher.waldon.dev@gmail.com>
Date: Mon, 14 Nov 2022 09:53:10 -0500
Subject: [PATCH] widget: do not allow invalid utf8 in editor

This commit replaces invalid UTF8 codepoints with the replacement character
when they are inserted into the editor. This ensures that the editor never
moves the editing gap to an invalid location and reads its contents.

Signed-off-by: Chris Waldon <christopher.waldon.dev@gmail.com>
---
 widget/buffer.go | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/widget/buffer.go b/widget/buffer.go
index 40e02a86..48ed72ed 100644
--- a/widget/buffer.go
+++ b/widget/buffer.go
@@ -6,6 +6,8 @@ import (
 	"io"
 	"strings"
 	"unicode/utf8"
+
+	"golang.org/x/text/runes"
 )
 
 // editBuffer implements a gap buffer for text editing.
@@ -162,6 +164,10 @@ func (e *editBuffer) String() string {
 }
 
 func (e *editBuffer) prepend(caret int, s string) {
+	if !utf8.ValidString(s) {
+		s = runes.ReplaceIllFormed().String(s)
+	}
+
 	e.moveGap(caret, len(s))
 	copy(e.text[caret:], s)
 	e.gapstart += len(s)