Add autofocus mode.

internal/preferences/protocol_test.go

@@ -191,3 +191,19 @@ func TestCapitalCheckboxesRoundTrip(t *testing.T) {
 		}
 	}
 }
+
+func TestStructuralFocusValuesRoundTrip(t *testing.T) {
+	settings := config.DefaultSettings()
+	values := FromSettings(settings)
+	if values.StructuralNavigationTriggersFocusMode {
+		t.Fatal("automatic structural focus defaults on")
+	}
+	values.StructuralNavigationTriggersFocusMode = true
+	merged, err := values.Merge(settings)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !FromSettings(merged).StructuralNavigationTriggersFocusMode {
+		t.Fatal("preference lost during Apply")
+	}
+}