Method dragFilesEnter

examples/Showcase/examples_frame.cpp:155–160

  std::string dragDropFileExtensionRegex() override { return ".*"; }

  void dragFilesEnter(const std::vector<std::string>& paths) override {
    dragging_ = true;
    dropped_ = false;
    filename_ = visage::fileName(paths[0]);
    redraw();
  }

  void dragFilesExit() override {
    dragging_ = false;