samples/dll/my_dll.cpp

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        my_dll.cpp
   3 // Purpose:     Sample showing how to use wx from a DLL
   4 // Author:      Vaclav Slavik
   5 // Created:     2009-12-03
   6 // RCS-ID:      $Id$
   7 // Copyright:   (c) 2009 Vaclav Slavik
   8 // Licence:     wxWindows licence
   9 /////////////////////////////////////////////////////////////////////////////
  10
  11 // ============================================================================
  12 // declarations
  13 // ============================================================================
  14
  15 // ----------------------------------------------------------------------------
  16 // headers
  17 // ----------------------------------------------------------------------------
  18
  19 #include "wx/wxprec.h"
  20
  21 #ifdef __BORLANDC__
  22     #pragma hdrstop
  23 #endif
  24
  25 #ifndef __WINDOWS__
  26     #error "This sample is Windows-only"
  27 #endif
  28
  29 #include "wx/app.h"
  30 #include "wx/dynlib.h"
  31 #include "wx/frame.h"
  32 #include "wx/panel.h"
  33 #include "wx/sizer.h"
  34 #include "wx/stattext.h"
  35 #include "wx/button.h"
  36 #include "wx/thread.h"
  37 #include "wx/msgdlg.h"
  38 #include "wx/msw/wrapwin.h"
  39
  40 #include <process.h> // for _beginthreadex()
  41
  42 #include "my_dll.h"
  43
  44 // ----------------------------------------------------------------------------
  45 // GUI classes
  46 // ----------------------------------------------------------------------------
  47
  48 class MyDllFrame : public wxFrame
  49 {
  50 public:
  51     MyDllFrame(wxWindow *parent, const wxString& label);
  52
  53     void OnAbout(wxCommandEvent& event);
  54
  55     DECLARE_EVENT_TABLE()
  56 };
  57
  58
  59 static const int CMD_SHOW_WINDOW = wxNewId();
  60 static const int CMD_TERMINATE = wxNewId();
  61
  62 class MyDllApp : public wxApp
  63 {
  64 public:
  65     MyDllApp();
  66
  67 private:
  68     void OnShowWindow(wxThreadEvent& event);
  69     void OnTerminate(wxThreadEvent& event);
  70 };
  71
  72
  73 // ============================================================================
  74 // implementation
  75 // ============================================================================
  76
  77 // ----------------------------------------------------------------------------
  78 // MyDllFrame
  79 // ----------------------------------------------------------------------------
  80
  81 BEGIN_EVENT_TABLE(MyDllFrame, wxFrame)
  82     EVT_BUTTON(wxID_ABOUT, MyDllFrame::OnAbout)
  83 END_EVENT_TABLE()
  84
  85 MyDllFrame::MyDllFrame(wxWindow *parent, const wxString& label)
  86     : wxFrame(parent, wxID_ANY, label)
  87 {
  88     wxPanel *p = new wxPanel(this, wxID_ANY);
  89     wxSizer *sizer = new wxBoxSizer(wxVERTICAL);
  90
  91     sizer->Add
  92            (
  93                new wxStaticText
  94                    (
  95                        p, wxID_ANY,
  96                        wxString::Format
  97                        (
  98                            "Running using %s\n"
  99                            "wxApp instance is %p, thread ID %ld",
 100                            wxVERSION_STRING,
 101                            wxApp::GetInstance(),
 102                            wxThread::GetCurrentId()
 103                        )
 104                    ),
 105                wxSizerFlags(1).Expand().Border(wxALL, 10)
 106            );
 107
 108     sizer->Add
 109            (
 110                new wxButton(p, wxID_ABOUT, "Show info"),
 111                wxSizerFlags(0).Right().Border(wxALL, 10)
 112            );
 113
 114     p->SetSizerAndFit(sizer);
 115
 116     wxSizer *fsizer = new wxBoxSizer(wxVERTICAL);
 117     fsizer->Add(p, wxSizerFlags(1).Expand());
 118     SetSizerAndFit(fsizer);
 119 }
 120
 121 void MyDllFrame::OnAbout(wxCommandEvent& WXUNUSED(event))
 122 {
 123     wxMessageBox("This window is running in its own thread,\n"
 124                  "using private wxWidgets instance compiled into the DLL.",
 125                  "About",
 126                  wxOK | wxICON_INFORMATION);
 127 }
 128
 129
 130 // ----------------------------------------------------------------------------
 131 // MyDllApp
 132 // ----------------------------------------------------------------------------
 133
 134 MyDllApp::MyDllApp()
 135 {
 136     // Keep the wx "main" thread running even without windows. This greatly
 137     // simplifies threads handling, because we don't have to correctly
 138     // implement wx-thread restarting.
 139     //
 140     // Note that this only works if you don't explicitly call ExitMainLoop(),
 141     // except in reaction to wx_dll_cleanup()'s message. wx_dll_cleanup()
 142     // relies on the availability of wxApp instance and if the event loop
 143     // terminated, wxEntry() would return and wxApp instance would be
 144     // destroyed.
 145     //
 146     // Also note that this is efficient, because if there are no windows, the
 147     // thread will sleep waiting for a new event. We could safe some memory
 148     // by shutting the thread down when it's no longer needed, though.
 149     SetExitOnFrameDelete(false);
 150
 151     Connect(CMD_SHOW_WINDOW,
 152             wxEVT_THREAD,
 153             wxThreadEventHandler(MyDllApp::OnShowWindow));
 154     Connect(CMD_TERMINATE,
 155             wxEVT_THREAD,
 156             wxThreadEventHandler(MyDllApp::OnTerminate));
 157 }
 158
 159 void MyDllApp::OnShowWindow(wxThreadEvent& event)
 160 {
 161     wxFrame *f = new MyDllFrame(NULL, event.GetString());
 162     f->Show(true);
 163 }
 164
 165 void MyDllApp::OnTerminate(wxThreadEvent& WXUNUSED(event))
 166 {
 167     ExitMainLoop();
 168 }
 169
 170
 171 // ----------------------------------------------------------------------------
 172 // application startup
 173 // ----------------------------------------------------------------------------
 174
 175 // we can't have WinMain() in a DLL and want to start the app ourselves
 176 IMPLEMENT_APP_NO_MAIN(MyDllApp)
 177
 178 namespace
 179 {
 180
 181 // Critical section that guards everything related to wxWidgets "main" thread
 182 // startup or shutdown.
 183 wxCriticalSection gs_wxStartupCS;
 184 // Handle of wx "main" thread if running, NULL otherwise
 185 HANDLE gs_wxMainThread = NULL;
 186
 187
 188 //  wx application startup code -- runs from its own thread
 189 unsigned wxSTDCALL MyAppLauncher(void* event)
 190 {
 191     // Note: The thread that called run_wx_gui_from_dll() holds gs_wxStartupCS
 192     //       at this point and won't release it until we signal it.
 193
 194     // We need to pass correct HINSTANCE to wxEntry() and the right value is
 195     // HINSTANCE of this DLL, not of the main .exe, use this MSW-specific wx
 196     // function to get it. Notice that under Windows XP and later the name is
 197     // not needed/used as we retrieve the DLL handle from an address inside it
 198     // but you do need to use the correct name for this code to work with older
 199     // systems as well.
 200     const HINSTANCE
 201         hInstance = wxDynamicLibrary::MSWGetModuleHandle("my_dll",
 202                                                          &gs_wxMainThread);
 203     if ( !hInstance )
 204         return 0; // failed to get DLL's handle
 205
 206     // IMPLEMENT_WXWIN_MAIN does this as the first thing
 207     wxDISABLE_DEBUG_SUPPORT();
 208
 209     // We do this before wxEntry() explicitly, even though wxEntry() would
 210     // do it too, so that we know when wx is initialized and can signal
 211     // run_wx_gui_from_dll() about it *before* starting the event loop.
 212     wxInitializer wxinit;
 213     if ( !wxinit.IsOk() )
 214         return 0; // failed to init wx
 215
 216     // Signal run_wx_gui_from_dll() that it can continue
 217     HANDLE hEvent = *(static_cast<HANDLE*>(event));
 218     if ( !SetEvent(hEvent) )
 219         return 0; // failed setting up the mutex
 220
 221     // Run the app:
 222     wxEntry(hInstance);
 223
 224     return 1;
 225 }
 226
 227 } // anonymous namespace
 228
 229 // ----------------------------------------------------------------------------
 230 // public DLL interface
 231 // ----------------------------------------------------------------------------
 232
 233 extern "C"
 234 {
 235
 236 void run_wx_gui_from_dll(const char *title)
 237 {
 238     // In order to prevent conflicts with hosting app's event loop, we
 239     // launch wx app from the DLL in its own thread.
 240     //
 241     // We can't even use wxInitializer: it initializes wxModules and one of
 242     // the modules it handles is wxThread's private module that remembers
 243     // ID of the main thread. But we need to fool wxWidgets into thinking that
 244     // the thread we are about to create now is the main thread, not the one
 245     // from which this function is called.
 246     //
 247     // Note that we cannot use wxThread here, because the wx library wasn't
 248     // initialized yet. wxCriticalSection is safe to use, though.
 249
 250     wxCriticalSectionLocker lock(gs_wxStartupCS);
 251
 252     if ( !gs_wxMainThread )
 253     {
 254         HANDLE hEvent = CreateEvent
 255                         (
 256                             NULL,  // default security attributes
 257                             FALSE, // auto-reset
 258                             FALSE, // initially non-signaled
 259                             NULL   // anonymous
 260                         );
 261         if ( !hEvent )
 262             return; // error
 263
 264         // NB: If your compiler doesn't have _beginthreadex(), use CreateThread()
 265         gs_wxMainThread = (HANDLE)_beginthreadex
 266                                   (
 267                                       NULL,           // default security
 268                                       0,              // default stack size
 269                                       &MyAppLauncher,
 270                                       &hEvent,        // arguments
 271                                       0,              // create running
 272                                       NULL
 273                                   );
 274
 275         if ( !gs_wxMainThread )
 276         {
 277             CloseHandle(hEvent);
 278             return; // error
 279         }
 280
 281         // Wait until MyAppLauncher signals us that wx was initialized. This
 282         // is because we use wxMessageQueue<> and wxString later and so must
 283         // be sure that they are in working state.
 284         WaitForSingleObject(hEvent, INFINITE);
 285         CloseHandle(hEvent);
 286     }
 287
 288     // Send a message to wx thread to show a new frame:
 289     wxThreadEvent *event =
 290         new wxThreadEvent(wxEVT_THREAD, CMD_SHOW_WINDOW);
 291     event->SetString(title);
 292     wxQueueEvent(wxApp::GetInstance(), event);
 293 }
 294
 295 void wx_dll_cleanup()
 296 {
 297     wxCriticalSectionLocker lock(gs_wxStartupCS);
 298
 299     if ( !gs_wxMainThread )
 300         return;
 301
 302     // If wx main thread is running, we need to stop it. To accomplish this,
 303     // send a message telling it to terminate the app.
 304     wxThreadEvent *event =
 305         new wxThreadEvent(wxEVT_THREAD, CMD_TERMINATE);
 306     wxQueueEvent(wxApp::GetInstance(), event);
 307
 308     // We must then wait for the thread to actually terminate.
 309     WaitForSingleObject(gs_wxMainThread, INFINITE);
 310     CloseHandle(gs_wxMainThread);
 311     gs_wxMainThread = NULL;
 312 }
 313
 314 } // extern "C"