// Purpose: topic overview
// Author: wxWidgets team
// RCS-ID: $Id$
-// Licence: wxWindows license
+// Licence: wxWindows licence
/////////////////////////////////////////////////////////////////////////////
-/*!
+/**
- @page overview_app wxApp overview
+@page overview_app wxApp Overview
- Classes: wxApp
+Classes: wxApp
- @li @ref overview_app_intro
- @li @ref overview_app_shutdown
+@li @ref overview_app_intro
+@li @ref overview_app_shutdown
- <hr>
+<hr>
- @section overview_app_intro Introduction
+@section overview_app_intro Introduction
- A wxWidgets application does not have a @e main procedure; the equivalent is the
- wxApp::OnInit member defined for a class derived from wxApp.
+A wxWidgets application does not have a @e main procedure; the equivalent is
+the wxApp::OnInit member defined for a class derived from wxApp.
- @e OnInit will usually create a top window as a bare minimum.
- Unlike in earlier versions of wxWidgets, OnInit does not return a frame. Instead it
- returns a boolean value which indicates whether processing should continue (@true)
- or not (@false). You call wxApp::SetTopWindow to let wxWidgets know about the top window.
+@e OnInit will usually create a top window as a bare minimum. Unlike in earlier
+versions of wxWidgets, OnInit does not return a frame. Instead it returns a
+boolean value which indicates whether processing should continue (@true) or not
+(@false).
- Note that the program's command line arguments, represented by @e argc
- and @e argv, are available from within wxApp member functions.
+Note that the program's command line arguments, represented by @e argc and
+@e argv, are available from within wxApp member functions.
- An application closes by destroying all windows. Because all frames must
- be destroyed for the application to exit, it is advisable to use parent
- frames wherever possible when creating new frames, so that deleting the
- top level frame will automatically delete child frames. The alternative
- is to explicitly delete child frames in the top-level frame's wxCloseEvent
- handler.
+An application closes by destroying all windows. Because all frames must be
+destroyed for the application to exit, it is advisable to use parent frames
+wherever possible when creating new frames, so that deleting the top level
+frame will automatically delete child frames. The alternative is to explicitly
+delete child frames in the top-level frame's wxCloseEvent handler.
- In emergencies the wxExit function can be called to kill the
- application however normally the application shuts down automatically,
- see @ref overview_app_shutdown.
+In emergencies the wxExit function can be called to kill the application
+however normally the application shuts down automatically, see
+@ref overview_app_shutdown.
- An example of defining an application follows:
+An example of defining an application follows:
- @code
- class DerivedApp : public wxApp
- {
- public:
- virtual bool OnInit();
- };
+@code
+class DerivedApp : public wxApp
+{
+public:
+ virtual bool OnInit();
+};
- IMPLEMENT_APP(DerivedApp)
+IMPLEMENT_APP(DerivedApp)
- bool DerivedApp::OnInit()
- {
- wxFrame *the_frame = new wxFrame(NULL, ID_MYFRAME, argv[0]);
- ...
- the_frame->Show(true);
- SetTopWindow(the_frame);
+bool DerivedApp::OnInit()
+{
+ wxFrame *the_frame = new wxFrame(NULL, ID_MYFRAME, argv[0]);
+ ...
+ the_frame->Show(true);
- return true;
- }
- @endcode
+ return true;
+}
+@endcode
- Note the use of IMPLEMENT_APP(appClass), which allows wxWidgets to dynamically create
- an instance of the application object at the appropriate point in wxWidgets initialization.
- Previous versions of wxWidgets used to rely on the creation of a global application object,
- but this is no longer recommended, because required global initialization may not have
- been performed at application object construction time.
+Note the use of IMPLEMENT_APP(appClass), which allows wxWidgets to dynamically
+create an instance of the application object at the appropriate point in
+wxWidgets initialization. Previous versions of wxWidgets used to rely on the
+creation of a global application object, but this is no longer recommended,
+because required global initialization may not have been performed at
+application object construction time.
- You can also use DECLARE_APP(appClass) in a header file to declare the wxGetApp function
- which returns a reference to the application object. Otherwise you can only use the global
- @c wxTheApp pointer which is of type @c wxApp *.
+You can also use DECLARE_APP(appClass) in a header file to declare the wxGetApp
+function which returns a reference to the application object. Otherwise you can
+only use the global @c wxTheApp pointer which is of type @c wxApp*.
+@section overview_app_shutdown Application Shutdown
- @section overview_app_shutdown Application shutdown
+The application normally shuts down when the last of its top level windows is
+closed. This is normally the expected behaviour and means that it is enough to
+call wxWindow::Close() in response to the "Exit" menu command if your program
+has a single top level window. If this behaviour is not desirable
+wxApp::SetExitOnFrameDelete can be called to change it.
- The application normally shuts down when the last of its top level windows is
- closed. This is normally the expected behaviour and means that it is enough to
- call wxWindow::Close() in response to the @c "Exit" menu command if your program has a
- single top level window. If this behaviour is not desirable wxApp::SetExitOnFrameDelete
- can be called to change it.
+Note that such logic doesn't apply for the windows shown before the program
+enters the main loop: in other words, you can safely show a dialog from
+wxApp::OnInit and not be afraid that your application terminates when this
+dialog -- which is the last top level window for the moment -- is closed.
- Note that such logic doesn't apply for the windows shown before the program enters the
- main loop: in other words, you can safely show a dialog from wxApp::OnInit and not be
- afraid that your application terminates when this dialog -- which is the last top level
- window for the moment -- is closed.
+Another aspect of the application shutdown is wxApp::OnExit which is called
+when the application exits but @e before wxWidgets cleans up its internal
+structures. You should delete all wxWidgets object that you created by the time
+OnExit finishes.
- Another aspect of the application shutdown is wxApp::OnExit
- which is called when the application exits but @e before wxWidgets cleans up
- its internal structures. You should delete all wxWidgets object that you
- created by the time OnExit finishes.
+In particular, do @b not destroy them from application class' destructor! For
+example, this code may crash:
- In particular, do @b not destroy them from application class' destructor!
- For example, this code may crash:
+@code
+class MyApp : public wxApp
+{
+public:
+ wxCHMHelpController m_helpCtrl;
+ ...
+};
+@endcode
- @code
- class MyApp : public wxApp
- {
- public:
- wxCHMHelpController m_helpCtrl;
- ...
- };
- @endcode
-
- The reason for that is that @c m_helpCtrl is a member object and is
- thus destroyed from MyApp destructor. But MyApp object is deleted after
- wxWidgets structures that wxCHMHelpController depends on were
- uninitialized! The solution is to destroy HelpCtrl in @e OnExit:
-
- @code
- class MyApp : public wxApp
- {
- public:
- wxCHMHelpController *m_helpCtrl;
- ...
- };
-
- bool MyApp::OnInit()
- {
- ...
- m_helpCtrl = new wxCHMHelpController;
- ...
- }
-
- int MyApp::OnExit()
- {
- delete m_helpCtrl;
- return 0;
- }
- @endcode
+The reason for that is that @c m_helpCtrl is a member object and is thus
+destroyed from MyApp destructor. But MyApp object is deleted after wxWidgets
+structures that wxCHMHelpController depends on were uninitialized! The solution
+is to destroy HelpCtrl in @e OnExit:
+
+@code
+class MyApp : public wxApp
+{
+public:
+ wxCHMHelpController *m_helpCtrl;
+ ...
+};
+
+bool MyApp::OnInit()
+{
+ ...
+ m_helpCtrl = new wxCHMHelpController;
+ ...
+}
+
+int MyApp::OnExit()
+{
+ delete m_helpCtrl;
+ return 0;
+}
+@endcode
*/
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