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1 | \section{wxApp overview}\label{wxappoverview} |
2 | ||
3 | Classes: \helpref{wxApp}{wxapp} | |
4 | ||
5 | A wxWindows application does not have a {\it main} procedure; the equivalent is the | |
6 | \rtfsp\helpref{OnInit}{wxapponinit} member defined for a class derived from wxApp.\rtfsp | |
7 | \rtfsp{\it OnInit} will usually create a top window as a bare minimum. | |
8 | ||
9 | Unlike in earlier versions of wxWindows, OnInit does not return a frame. Instead it | |
10 | returns a boolean value which indicates whether processing should continue (TRUE) or not (FALSE). | |
11 | You call \helpref{wxApp::SetTopWindow}{wxappsettopwindow} to let wxWindows know | |
12 | about the top window. | |
13 | ||
14 | Note that the program's command line arguments, represented by {\it | |
15 | argc} and {\it argv}, are available from within wxApp member functions. | |
16 | ||
17 | An application closes by destroying all windows. Because all frames must | |
18 | be destroyed for the application to exit, it is advisable to use parent | |
19 | frames wherever possible when creating new frames, so that deleting the | |
20 | top level frame will automatically delete child frames. The alternative | |
21 | is to explicitly delete child frames in the top-level frame's \helpref{wxWindow::OnCloseWindow}{wxwindowonclosewindow}\rtfsp | |
22 | handler. | |
23 | ||
24 | In emergencies the \helpref{wxExit}{wxexit} function can be called to kill the | |
25 | application. | |
26 | ||
27 | An example of defining an application follows: | |
28 | ||
29 | \begin{verbatim} | |
6e6110ee | 30 | class DerivedApp : public wxApp |
a660d684 | 31 | { |
6e6110ee VZ |
32 | public: |
33 | virtual bool OnInit(); | |
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34 | }; |
35 | ||
36 | IMPLEMENT_APP(DerivedApp) | |
37 | ||
6e6110ee | 38 | bool DerivedApp::OnInit() |
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39 | { |
40 | wxFrame *the_frame = new wxFrame(NULL, argv[0]); | |
41 | ... | |
42 | SetTopWindow(the_frame); | |
43 | ||
44 | return TRUE; | |
45 | } | |
46 | \end{verbatim} | |
47 | ||
48 | Note the use of IMPLEMENT\_APP(appClass), which allows wxWindows to dynamically create an instance of the application object | |
49 | at the appropriate point in wxWindows initialization. Previous versions of wxWindows used | |
50 | to rely on the creation of a global application object, but this is no longer recommended, | |
51 | because required global initialization may not have been performed at application object | |
52 | construction time. | |
53 | ||
54 | You can also use DECLARE\_APP(appClass) in a header file to declare the wxGetApp function which returns | |
55 | a reference to the application object. | |
56 |