widget: take deleted runes into account when applying Editor.MaxLen

Signed-off-by: Elias Naur <mail@eliasnaur.com>

widget/editor.go

@@ -1262,11 +1262,12 @@ func (e *Editor) replace(start, end int, s string, addHistory bool) int {
 	startPos := e.closestPosition(combinedPos{runes: start})
 	endPos := e.closestPosition(combinedPos{runes: end})
 	startOff := e.runeOffset(startPos.runes)
+	replaceSize := endPos.runes - startPos.runes
 	el := e.Len()
 	var sc int
 	idx := 0
 	for idx < len(s) {
-		if e.MaxLen > 0 && el+sc >= e.MaxLen {
+		if e.MaxLen > 0 && el-replaceSize+sc >= e.MaxLen {
 			s = s[:idx]
 			break
 		}
@@ -1279,7 +1280,6 @@ func (e *Editor) replace(start, end int, s string, addHistory bool) int {
 		sc++
 	}
 	newEnd := startPos.runes + sc
-	replaceSize := endPos.runes - startPos.runes
 
 	if addHistory {
 		e.rr.Seek(int64(startOff), 0)

widget/editor_test.go

@@ -1019,7 +1019,7 @@ func TestEditor_MaxLen(t *testing.T) {
 		Ops:         new(op.Ops),
 		Constraints: layout.Exact(image.Pt(100, 100)),
 		Queue: newQueue(
-			key.EditEvent{Range: key.Range{Start: 0, End: 0}, Text: "1234"},
+			key.EditEvent{Range: key.Range{Start: 0, End: 2}, Text: "1234"},
 			key.SelectionEvent{Start: 4, End: 4},
 		),
 	}
@@ -1031,7 +1031,7 @@ func TestEditor_MaxLen(t *testing.T) {
 	if got, want := e.Text(), "12345678"; got != want {
 		t.Errorf("editor failed to cap EditEvent")
 	}
-	if start, end := e.Selection(); start != 1 || end != 1 {
+	if start, end := e.Selection(); start != 3 || end != 3 {
 		t.Errorf("editor failed to adjust SelectionEvent")
 	}
 }