1. 一个wxWidgets的基本结构是：一个App类+一个Frame类，代码如：
class MyApp: public wxApp{public: bool OnInit();};IMPLEMENT_APP(MyApp)
2. IMPLEMENT_APP(MyApp) 这个宏包含了入口，抽象了不同平台入口的差异，分析如下:
IMPLEMENT_APP展开如下:
#define IMPLEMENT_APP(appname) \ IMPLEMENT_APP_NO_THEMES(appname) \ IMPLEMENT_WX_THEME_SUPPORT
IMPLEMENT_APP_NO_THEMES展开如下:
#define IMPLEMENT_APP_NO_THEMES(appname) \ IMPLEMENT_APP_NO_MAIN(appname) \ IMPLEMENT_WXWIN_MAIN
IMPLEMENT_APP_NO_MAIN展开如下:
#define IMPLEMENT_APP_NO_MAIN(appname) \ wxAppConsole *wxCreateApp() \ { \ wxAppConsole::CheckBuildOptions(WX_BUILD_OPTIONS_SIGNATURE, \ "your program"); \ return new appname; \ } \ wxAppInitializer \ wxTheAppInitializer((wxAppInitializerFunction) wxCreateApp); \ DECLARE_APP(appname) \ appname& wxGetApp() { return *wx_static_cast(appname*, wxApp::GetInstance()); }
实际上IMPLEMENT_APP_NO_MAIN定义了wxCreateApp函数new appname创建出应用类的实例.
wxAppInitializer wxTheAppInitializer((wxAppInitializerFunction) wxCreateApp);实际上把创建函数wxCreateApp用接口wxApp::SetInitializerFunction(fn);设置进了系统，都静态变量保存的.
appname& wxGetApp() { return *wx_static_cast(appname*, wxApp::GetInstance()); }这个获取App实例的接口也在此定义.
IMPLEMENT_WXWIN_MAIN展开如下：
#define IMPLEMENT_WXWIN_MAIN \ extern "C" int WINAPI WinMain(HINSTANCE hInstance, \ HINSTANCE hPrevInstance, \ wxCmdLineArgType lpCmdLine, \ int nCmdShow) \ { \ return wxEntry(hInstance, hPrevInstance, lpCmdLine, nCmdShow); \ } \ IMPLEMENT_WXWIN_MAIN_BORLAND_NONSTANDARD
WinMain是Windows平台Win32应用的入口函数，WinMain包含了C/C++的main函数实现.
多参WXDLLEXPORT int wxEntry(HINSTANCE hInstance,HINSTANCE WXUNUSED(hPrevInstance),wxCmdLineArgType WXUNUSED(pCmdLine),int nCmdShow)，会在最后调用2参的int wxEntry(int& argc, char **argv)，此函数实现有3处，Unicode版本的也是要转换成非Unicode版本的函数调用，最终会调用到wxEntryReal，此接口是真正的库初始化入口：分析如下
wxEntryReal定义如下：
int wxEntryReal(int& argc, wxChar **argv){ // library initialization wxInitializer initializer(argc, argv); if ( !initializer.IsOk() ) {#if wxUSE_LOG // flush any log messages explaining why we failed delete wxLog::SetActiveTarget(NULL);#endif return -1; } wxTRY { // app initialization if ( !wxTheApp->CallOnInit() ) { // don't call OnExit() if OnInit() failed return -1; } // ensure that OnExit() is called if OnInit() had succeeded class CallOnExit { public: ~CallOnExit() { wxTheApp->OnExit(); } } callOnExit; WX_SUPPRESS_UNUSED_WARN(callOnExit); // app execution return wxTheApp->OnRun(); } wxCATCH_ALL( wxTheApp->OnUnhandledException(); return -1; )}
wxInitializer initializer(argc, argv);这句隐含了库的初始化过程，wxInitializer类的构造函数进行了初始化：
wxInitializer(int argc, char **argv) //构造函数 { m_ok = wxInitialize(argc, argv); //调用了初始化wxInitialize }
wxInitialize调用了wxEntryStart，此函数也2个版本，unicode的版本也是经过转换调用的非unicode版本，如下：
wxAppPtr app(wxTheApp); if ( !app.get() ) { // if not, he might have used IMPLEMENT_APP() to give us a function to // create it wxAppInitializerFunction fnCreate = wxApp::GetInitializerFunction(); // 注意此句取得了上边设置的创建App的函数 if ( fnCreate ) { // he did, try to create the custom wxApp object app.Set((*fnCreate)()); // 此处构造了应用App类，app变量保存了此指针，这个赋值实际调用wxApp::SetInstance(ptr);赋值了ms_appInstance，
//通过wxTheApp宏访问，上边定义的wxGetApp接口，也是获取此变量. } if ( !app.get() ) { // either IMPLEMENT_APP() was not used at all or it failed -- in any // case we still need something app.Set(new wxDummyConsoleApp); } // wxApp initialization: this can be customized // -------------------------------------------- if ( !app->Initialize(argc, argv) ) // 调用app初始化接口，bool wxApp::Initialize(int& argc, wxChar **argv)此接口被调用，进而初始化了系统 { return false; }
wxEntryReal调用了系统初始化后，又调用了应用App的OnInit接口，给App初始化的时机：
// app initialization if ( !wxTheApp->CallOnInit() ) { // don't call OnExit() if OnInit() failed return -1; }此调用会多态到应用的OnInit接口，应用在此接口中初始化了Frame主窗口之类的窗口组件.wxTheApp宏用的比较多.CallOnInit接口调用了 CallOnInit() { return OnInit(); }接口。
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以上基本完成了库和用户的App初始化过程，在wxEntryReal接口的最后，return wxTheApp->OnRun()；进入:
int wxAppBase::OnRun(){ // see the comment in ctor: if the initial value hasn't been changed, use // the default Yes from now on if ( m_exitOnFrameDelete == Later ) { m_exitOnFrameDelete = Yes; } //else: it has been changed, assume the user knows what he is doing return MainLoop(); }//进入了程序主循环，开始了事件接收、分发、处理的过程，指导程序结束.
本文完.
转载于:https://www.cnblogs.com/linucos/archive/2012/08/19/2646543.html
