onTapDown method
Implementation
void onTapDown(TapDownDetails details) {
// 如果没有点中任何文字,则取消选择
final selectedId = _textLayerManager.selectLayerAt(
details.localPosition,
_canvasSize ?? Size.zero,
);
if (selectedId == null) {
_textLayerManager.clearSelection();
notifyListeners();
} else {
notifyListeners();
}
}