allow to change the event propagation level (modified patch 743086)

[wxWidgets.git] / docs / latex / wx / tapp.tex

diff --git a/docs/latex/wx/tapp.tex b/docs/latex/wx/tapp.tex
index f9f7ef402615de00e24a2397d0fe88cc5d47e732..f748843b83e05279c51d95cec3b48c5333fd10a3 100644 (file)
--- a/docs/latex/wx/tapp.tex
+++ b/docs/latex/wx/tapp.tex
@@ -7,12 +7,12 @@ A wxWindows application does not have a {\it main} procedure; the equivalent is
 \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
@@ -22,7 +22,8 @@ is to explicitly delete child frames in the top-level frame's \helpref{wxCloseEv
 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:
 
@@ -37,11 +38,12 @@ IMPLEMENT_APP(DerivedApp)
 
 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}
 
@@ -54,3 +56,61 @@ 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.
 
+\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:
+
+\begin{verbatim}
+class MyApp : public wxApp
+{
+ public:
+    wxCHMHelpController m_helpCtrl;
+    ...
+};
+\end{verbatim}
+
+The reason for that is that {\tt m\_helpCtrl} is a member object and is 
+thus destroyed from MyApp destructor. But MyApp object is deleted after 
+wxWindows structures that wxCHMHelpController depends on were 
+uninitialized! The solution is to destroy HelpCtrl in {\it OnExit}:
+
+\begin{verbatim}
+class MyApp : public wxApp
+{
+ public:
+    wxCHMHelpController *m_helpCtrl;
+    ...
+};
+
+bool MyApp::OnInit()
+{
+  ...
+  m_helpCtrl = new wxCHMHelpController;
+  ...
+}
+
+int MyApp::OnExit()
+{
+  delete m_helpCtrl;
+  return 0;
+}
+\end{verbatim}