Add a helper for recognizing printable keys

Two places test for "a character the user typed" by hand, and a third
one is about to be needed. Give the test a name.

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

pkg/gocui/edit.go

@@ -78,7 +78,7 @@ func SimpleEditor(v *View, key Key) bool {
 		v.TextArea.GoToEndOfLine()
 	case key.Equals(NewKeyStrMod("y", ModCtrl)):
 		v.TextArea.Yank()
-	case key.Str() != "" && key.Mod() == 0:
+	case key.IsPrintable():
 		v.TextArea.TypeCharacter(key.Str())
 	default:
 		return false

pkg/gocui/gui.go

@@ -2097,7 +2097,7 @@ func (g *Gui) matchView(v *View, kb *keybinding) bool {
 	if v == nil {
 		return false
 	}
-	if v.Editable && kb.key.Str() != "" && kb.key.Mod() == 0 {
+	if v.Editable && kb.key.IsPrintable() {
 		return false
 	}
 	if kb.viewName != v.name {

pkg/gocui/key.go

@@ -61,6 +61,12 @@ func (k Key) IsSet() bool {
 	return k.keyName != 0
 }
 
+// IsPrintable reports whether the key stands for a character that can be typed
+// into a text field.
+func (k Key) IsPrintable() bool {
+	return k.keyName == KeyName(tcell.KeyRune) && k.str != "" && k.mod == ModNone
+}
+
 func (k Key) Equals(otherKey Key) bool {
 	return k.keyName == otherKey.keyName && k.str == otherKey.str && k.mod == otherKey.mod
 }

pkg/gocui/key_test.go

@@ -0,0 +1,16 @@
+package gocui
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestKeyIsPrintable(t *testing.T) {
+	assert.True(t, NewKeyRune('x').IsPrintable())
+	assert.True(t, NewKeyRune('界').IsPrintable())
+	assert.True(t, NewKeyRune(' ').IsPrintable())
+	assert.False(t, NewKeyStrMod("x", ModCtrl).IsPrintable())
+	assert.False(t, NewKeyName(KeyEnter).IsPrintable())
+	assert.False(t, Key{}.IsPrintable())
+}