\rtfsp{\it OnInit} will usually create a top window as a bare minimum.
Unlike in earlier versions of wxWindows, OnInit does not return a frame. Instead it
-returns a boolean value which indicates whether processing should continue (TRUE) or not (FALSE).
+returns a boolean value which indicates whether processing should continue (true) or not (false).
You call \helpref{wxApp::SetTopWindow}{wxappsettopwindow} to let wxWindows know
about the top window.
-Note that the program's command line arguments, represented by {\it
-argc} and {\it argv}, are available from within wxApp member functions.
+Note that the program's command line arguments, represented by {\it argc}
+and {\it 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
handler.
In emergencies the \helpref{wxExit}{wxexit} function can be called to kill the
-application.
+application however normally the applications shuts down automatically,
+\helpref{see below}{wxappshutdownoverview}.
An example of defining an application follows:
bool DerivedApp::OnInit()
{
- wxFrame *the_frame = new wxFrame(NULL, argv[0]);
+ wxFrame *the_frame = new wxFrame(NULL, ID_MYFRAME, argv[0]);
...
+ the_frame->Show(true);
SetTopWindow(the_frame);
- return TRUE;
+ return true;
}
\end{verbatim}
You can also use DECLARE\_APP(appClass) in a header file to declare the wxGetApp function which returns
a reference to the application object.
-\subsection{Application shutdown}
-
-\helpref{OnExit}{wxapponexit} is called when the application exits but {\it before}
-wxWindows cleans its internal structures. Your should delete all wxWindows object that
-your created by the time OnExit finishes. In particular, do {\bf not} destroy them
+\subsection{Application shutdown}\label{wxappshutdownoverview}
+
+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 \helpref{Close()}{wxwindowclose} in response to the {\tt "Exit"} menu
+command if your program has a single top level window. If this behaviour is not
+desirable \helpref{wxApp::SetExitOnFrameDelete}{wxappsetexitonframedelete} can
+be called to change it. Note that starting from wxWindows 2.3.3 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
+\helpref{wxApp::OnInit}{wxapponinit} 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 the \helpref{OnExit}{wxapponexit}
+which is called when the application exits but {\it before} wxWindows cleans up
+its internal structures. Your should delete all wxWindows object that your
+created by the time OnExit finishes. In particular, do {\bf not} destroy them
from application class' destructor!
For example, this code may crash: