{"id":4242,"date":"2022-02-09T09:47:45","date_gmt":"2022-02-09T09:47:45","guid":{"rendered":"http:\/\/truelogic.org\/wordpress\/?p=4242"},"modified":"2022-02-09T09:47:46","modified_gmt":"2022-02-09T09:47:46","slug":"13e-wxwidgets-persistent-objects","status":"publish","type":"post","link":"https:\/\/truelogic.org\/wordpress\/2022\/02\/09\/13e-wxwidgets-persistent-objects\/","title":{"rendered":"13e. wxWidgets – Persistent Objects"},"content":{"rendered":"\n

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

Persistent objects are widgets in wxWidgets which have the ability to save and restore their visual state between different program invocations. For instance, if a window is moved or sized during a program run, then using persistence we can restore the window to the same state during subsequent runs.<\/p>\n\n\n\n

Only a few wxWidgets classes have this ability so far : top level windows like wxFrame, wxDialog and objects which are based on wxBookCtrlBase like wxNoteBook, wxListBook etc.<\/p>\n\n\n\n

Apart from the existing classes which support persistence, you can add persistence to your own custom wxWidget classes too.<\/p>\n\n\n\n

In the sample code below, we create a simple wxFrame and restore it back if it was saved. The three screenshots are for the first initial load, then moving and resizing it, exiting and running it a second time.<\/p>\n\n\n\n

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

persistent.h<\/pre>\n\n\n
\n#include <wx\/wxprec.h>\n#ifndef WX_PRECOMP\n\t#include <wx\/wx.h>\n#endif\n\nclass Persistent:public wxFrame {\n\n\tpublic:\n\t\tPersistent(const wxString &title);\n};\n<\/pre><\/div>\n\n\n
persistent.cpp<\/pre>\n\n\n
\n#include "persistent.h"\n\n\nPersistent::Persistent(const wxString& title):\n\twxFrame(NULL, -1, title, wxDefaultPosition, wxSize(500,200)) {\n        Center();\n\n}\n<\/pre><\/div>\n\n\n
main.h<\/pre>\n\n\n
\n#include <wx\/wxprec.h>\n#ifndef WX_PRECOMP\n\t#include <wx\/wx.h>\n#endif\n\nclass Main: public wxApp {\n\n\tpublic:\n\t\tvirtual bool OnInit();\n};\n<\/pre><\/div>\n\n\n
main.cpp<\/pre>\n\n\n
\n#include "main.h"\n#include "persistent.h"\n#include <wx\/persist.h>\n#include <wx\/persist\/toplevel.h>\n\nIMPLEMENT_APP(Main)\n\nbool Main::OnInit() {\n\tPersistent *app = new Persistent(wxT("Persistent Objects"));\n\tapp->SetName(wxT("testobject"));\n\tif (!wxPersistenceManager::Get().RegisterAndRestore((wxFrame*) app))\n\t\tapp->Show(true);\n\telse\n\t\tapp->Show(true);\n}\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 Persistent objects are widgets in wxWidgets which have the ability to save and restore their visual state between different program invocations. For instance, if […]<\/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-4242","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\/4242","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=4242"}],"version-history":[{"count":5,"href":"https:\/\/truelogic.org\/wordpress\/wp-json\/wp\/v2\/posts\/4242\/revisions"}],"predecessor-version":[{"id":4250,"href":"https:\/\/truelogic.org\/wordpress\/wp-json\/wp\/v2\/posts\/4242\/revisions\/4250"}],"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=4242"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/truelogic.org\/wordpress\/wp-json\/wp\/v2\/categories?post=4242"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/truelogic.org\/wordpress\/wp-json\/wp\/v2\/tags?post=4242"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}