57 lines
2.1 KiB
TeX
57 lines
2.1 KiB
TeX
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\section{wxApp overview}\label{wxappoverview}
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Classes: \helpref{wxApp}{wxapp}
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A wxWindows application does not have a {\it main} procedure; the equivalent is the
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\rtfsp\helpref{OnInit}{wxapponinit} member defined for a class derived from wxApp.\rtfsp
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\rtfsp{\it OnInit} will usually create a top window as a bare minimum.
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Unlike in earlier versions of wxWindows, OnInit does not return a frame. Instead it
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returns a boolean value which indicates whether processing should continue (TRUE) or not (FALSE).
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You call \helpref{wxApp::SetTopWindow}{wxappsettopwindow} to let wxWindows know
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about the top window.
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Note that the program's command line arguments, represented by {\it
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argc} and {\it argv}, are available from within wxApp member functions.
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An application closes by destroying all windows. Because all frames must
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be destroyed for the application to exit, it is advisable to use parent
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frames wherever possible when creating new frames, so that deleting the
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top level frame will automatically delete child frames. The alternative
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is to explicitly delete child frames in the top-level frame's \helpref{wxWindow::OnCloseWindow}{wxwindowonclosewindow}\rtfsp
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handler.
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In emergencies the \helpref{wxExit}{wxexit} function can be called to kill the
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application.
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An example of defining an application follows:
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\begin{verbatim}
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class DerivedApp: public wxApp
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{
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public:
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bool OnInit(void);
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};
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IMPLEMENT_APP(DerivedApp)
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bool DerivedApp::OnInit(void)
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{
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wxFrame *the_frame = new wxFrame(NULL, argv[0]);
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...
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SetTopWindow(the_frame);
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return TRUE;
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}
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\end{verbatim}
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Note the use of IMPLEMENT\_APP(appClass), which allows wxWindows to dynamically create an instance of the application object
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at the appropriate point in wxWindows initialization. Previous versions of wxWindows used
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to rely on the creation of a global application object, but this is no longer recommended,
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because required global initialization may not have been performed at application object
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construction time.
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You can also use DECLARE\_APP(appClass) in a header file to declare the wxGetApp function which returns
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a reference to the application object.
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