OpenFileDialogShowWindowModal.cpp

#include <wx/wx.h>
#include <wx/filedlg.h>
#include <wx/sysopt.h>
#include <wx/windowptr.h>

// Workaround : with wxWidgets version <= 3.2.0 wxFileDialog ShowWindowModal method doesn't exists on other platform that macOS
#if defined(__APPLE__)
using FileDialog = wxFileDialog;
#else
class FileDialog : public wxFileDialog {
public:
  FileDialog(wxWindow* parent, const wxString& message = wxFileSelectorPromptStr, const wxString& defaultDir = wxEmptyString, const wxString& defaultFile = wxEmptyString, const wxString& wildCard = wxFileSelectorDefaultWildcardStr, long style = wxFD_DEFAULT_STYLE, const wxPoint& pos = wxDefaultPosition, const wxSize& sz = wxDefaultSize, const wxString& name = wxFileDialogNameStr) : wxFileDialog(parent, message, defaultDir, defaultFile, wildCard, style, pos, sz, name) {}
  void ShowWindowModal() {
    SetReturnCode(ShowModal());
    wxWindowModalDialogEvent event(wxEVT_WINDOW_MODAL_DIALOG_CLOSED, this->GetId());
    event.SetEventObject(this);
    wxPostEvent(this, event);
  }
};
#endif

namespace OpenFileDialogShowWindowModalExample {
  class Frame : public wxFrame {
  public:
    Frame() : wxFrame(nullptr, wxID_ANY, "OpenFileDialog (ShowWindowModal) example") {
      button->Bind(wxEVT_BUTTON, [&](wxCommandEvent& event) {
        wxWindowPtr<FileDialog> openFileDialog(new FileDialog(this, wxEmptyString, wxEmptyString, wxEmptyString, "Text Files (*.txt)|*.txt|All Files (*.*)|*.*", wxFD_OPEN|wxFD_FILE_MUST_EXIST));
        openFileDialog->SetFilterIndex(0);
        openFileDialog->ShowWindowModal();
        openFileDialog->Bind(wxEVT_WINDOW_MODAL_DIALOG_CLOSED, [this,openFileDialog](wxWindowModalDialogEvent& event) {
          if (event.GetReturnCode() == wxID_OK)
            label->SetLabelText(wxString::Format("File = %s",  openFileDialog->GetPath()));
        });
      });
      
    }

  private:
    wxPanel* panel = new wxPanel {this};
    wxButton* button = new wxButton(panel, wxID_ANY, "Open...", {10, 10});
    wxStaticText* label = new wxStaticText(panel, wxID_ANY, "", {10, 40});
  };

  class Application : public wxApp {
    bool OnInit() override {
      wxSystemOptions::SetOption("osx.openfiledialog.always-show-types", 1);
      return (new Frame)->Show();
    }
  };
}

wxIMPLEMENT_APP(OpenFileDialogShowWindowModalExample::Application);