{"id":3974,"date":"2021-12-25T17:13:09","date_gmt":"2021-12-25T17:13:09","guid":{"rendered":"http:\/\/truelogic.org\/wordpress\/?p=3974"},"modified":"2021-12-25T17:13:11","modified_gmt":"2021-12-25T17:13:11","slug":"6e-wxwidgets-vetoing-events","status":"publish","type":"post","link":"https:\/\/truelogic.org\/wordpress\/2021\/12\/25\/6e-wxwidgets-vetoing-events\/","title":{"rendered":"6e. wxWidgets – Vetoing Events"},"content":{"rendered":"\n

OVERVIEW<\/strong><\/p>\n\n\n\n

Continuing from the previous section where we looked at event propagation, in this section we see how to cancel processing events. Event processing may be cancelled by either the Veto()<\/em> method or Skip(false) <\/em>method. Events derived from wxCommandEvent do not have a Veto<\/em> method. They use the Skip<\/em> method. Events which are not derived from wxCommandEvent have a Veto<\/em> method(). If you dont specify the false argument in Skip()<\/em> then the event is propagated.<\/p>\n\n\n\n

The sample code below uses Skip<\/em> to veto command events and Veto<\/em> to cancel a wxCloseEvent.<\/p>\n\n\n\n

SAMPLE CODE<\/strong><\/p>\n\n\n\n

events-veto.h<\/pre>\n\n\n
\n#include <wx\/wxprec.h>\n#ifndef WX_PRECOMP\n    #include <wx\/wx.h>\n#endif\n\nclass EventsVeto: public wxFrame {\n\n    public:\n      EventsVeto(const wxString &title);\n      void OnClose(wxCloseEvent &event);\n      void OnClick(wxCommandEvent &event);\n      void OnClick2(wxCommandEvent &event);\n      void OnClick3(wxCommandEvent &event);\n      void OnClick4(wxCommandEvent &event);\n \n};\n\nconst int ID_PANEL_1 = 101;\nconst int ID_PANEL_1_1 = 102;\nconst int ID_BUTTON_1 = 200;\n\n<\/pre><\/div>\n\n\n
events-veto.cpp<\/pre>\n\n\n
\n#include "events-veto.h"\n\n\nEventsVeto::EventsVeto(const wxString &title):\n\n    wxFrame(NULL, -1, title, wxDefaultPosition, wxSize(500,200)) {\n\n    this->Bind(wxEVT_CLOSE_WINDOW, &EventsVeto::OnClose, this);\n\n    wxPanel *basePanel = new wxPanel(this, -1);\n    wxBoxSizer *baseSizer = new wxBoxSizer(wxVERTICAL);\n    basePanel->SetSizer(baseSizer);\n\n    wxPanel *panel1 = new wxPanel(basePanel, ID_PANEL_1);\n    panel1->SetBackgroundColour(wxColour(100,200,100));\n    wxBoxSizer *vbox = new wxBoxSizer(wxVERTICAL);\n    panel1->SetSizer(vbox);\n\n    wxPanel *panel11 = new wxPanel(panel1, ID_PANEL_1_1);\n    panel11->SetBackgroundColour(wxColour(50,180,45));\n    wxBoxSizer *hbox = new wxBoxSizer(wxHORIZONTAL);\n    panel11->SetSizer(hbox);\n\n    wxButton *btn = new wxButton(panel11, ID_BUTTON_1, wxT("Click this button"));\n    hbox->Add(btn, 0, wxALIGN_CENTER);\n\n    vbox->Add(panel11, 1, wxALL | wxEXPAND, 50);\n\n    baseSizer->Add(panel1, 1, wxALL | wxEXPAND,5);\n\n    btn->Bind(wxEVT_BUTTON, &EventsVeto::OnClick, this);\n    panel11->Bind(wxEVT_COMMAND_BUTTON_CLICKED, &EventsVeto::OnClick2, this);\n    panel1->Bind(wxEVT_COMMAND_BUTTON_CLICKED, &EventsVeto::OnClick3, this);\n    this->Bind(wxEVT_COMMAND_BUTTON_CLICKED, &EventsVeto::OnClick4, this);\n\n    Center();\n\n}\n\nvoid EventsVeto::OnClose(wxCloseEvent &event) {\n     wxMessageDialog *dlg = new wxMessageDialog(NULL,\n     \t wxT("Are you sure you want to close?"), wxT("Question"), wxYES_NO);\n\n     int retVal = dlg->ShowModal();\n     dlg->Destroy();\n     if (retVal == wxID_NO) {\n       event.Veto();\n       return;\n     }\n     Destroy();\n\n}\n\nvoid EventsVeto::OnClick(wxCommandEvent &event) {\n\n     wxMessageDialog *dlg = new wxMessageDialog(NULL,\n     \t wxT("Veto at the button level?"), wxT("Question"), wxYES_NO);\n\n     int retVal = dlg->ShowModal();\n     dlg->Destroy();\n     if (retVal == wxID_YES) {\n       event.Skip(false);\n       return;\n     }\n     wxString msg= "Click detected in btn ";\n     wxMessageBox(msg);\n\n     event.Skip();\n}\n\nvoid EventsVeto::OnClick2(wxCommandEvent &event) {\n     wxMessageDialog *dlg = new wxMessageDialog(NULL,\n     \t wxT("Veto at the panel11 level?"), wxT("Question"), wxYES_NO);\n\n     int retVal = dlg->ShowModal();\n     dlg->Destroy();\n     if (retVal == wxID_YES) {\n       event.Skip(false);\n       return;\n     }\n\n\twxString msg= "Click detected in panel11 ";\n\twxMessageBox(msg);\n\tevent.Skip();\n\n}\n\nvoid EventsVeto::OnClick3(wxCommandEvent &event) {\n     wxMessageDialog *dlg = new wxMessageDialog(NULL,\n     \t wxT("Veto at the panel1 level?"), wxT("Question"), wxYES_NO);\n\n     int retVal = dlg->ShowModal();\n     dlg->Destroy();\n     if (retVal == wxID_YES) {\n       event.Skip(false);\n       return;\n     }\n\n\twxString msg= "Click detected in panel1";\n\twxMessageBox(msg);\n\tevent.Skip();\n\n}\n\nvoid EventsVeto::OnClick4(wxCommandEvent &event) {\n\twxString msg= "Click detected in window frame ";\n\twxMessageBox(msg);\n}\n\n<\/pre><\/div>\n\n\n
main.h<\/pre>\n\n\n
\n#include <wx\/wxprec.h>\n#ifndef WX_PRECOMP\n    #include <wx\/wx.h>\n#endif\n\nclass Main: public wxApp {\n\n\tpublic:\n\t        virtual bool OnInit();\n};\n<\/pre><\/div>\n\n\n
main.cpp<\/pre>\n\n\n
\n#include "main.h"\n#include "events-veto.h"\n \nIMPLEMENT_APP(Main)\n\nbool Main::OnInit() {\n\n    EventsVeto *app = new EventsVeto(wxT("Events Veto"));\n    app->Show(true);\n}\n<\/pre><\/div>\n\n\n
The output is shown below<\/p>\n\n\n\n
\"\"<\/figure>\n\n\n\n
\"\"<\/figure>\n\n\n\n
\"\"<\/figure>\n","protected":false},"excerpt":{"rendered":"
OVERVIEW Continuing from the previous section where we looked at event propagation, in this section we see how to cancel processing events. Event processing may […]<\/a><\/p>\n<\/div>","protected":false},"author":1,"featured_media":3595,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[302,365],"tags":[],"class_list":["post-3974","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-cc","category-wxwidgets"],"_links":{"self":[{"href":"https:\/\/truelogic.org\/wordpress\/wp-json\/wp\/v2\/posts\/3974","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/truelogic.org\/wordpress\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/truelogic.org\/wordpress\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/truelogic.org\/wordpress\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/truelogic.org\/wordpress\/wp-json\/wp\/v2\/comments?post=3974"}],"version-history":[{"count":4,"href":"https:\/\/truelogic.org\/wordpress\/wp-json\/wp\/v2\/posts\/3974\/revisions"}],"predecessor-version":[{"id":3981,"href":"https:\/\/truelogic.org\/wordpress\/wp-json\/wp\/v2\/posts\/3974\/revisions\/3981"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/truelogic.org\/wordpress\/wp-json\/wp\/v2\/media\/3595"}],"wp:attachment":[{"href":"https:\/\/truelogic.org\/wordpress\/wp-json\/wp\/v2\/media?parent=3974"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/truelogic.org\/wordpress\/wp-json\/wp\/v2\/categories?post=3974"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/truelogic.org\/wordpress\/wp-json\/wp\/v2\/tags?post=3974"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}