| | 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} |
| | 30 | class DerivedApp: public wxApp |
| | 31 | { |
| | 32 | public: |
| | 33 | bool OnInit(void); |
| | 34 | }; |
| | 35 | |
| | 36 | IMPLEMENT_APP(DerivedApp) |
| | 37 | |
| | 38 | bool DerivedApp::OnInit(void) |
| | 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 | |
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