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 __WXMSW__
  26     #error "This sample is MSW-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(wxEVT_IDLE, wxIdleEventHandler(MyDllApp::OnIdle));
 152     Connect(CMD_SHOW_WINDOW,
 153             wxEVT_THREAD,
 154             wxThreadEventHandler(MyDllApp::OnShowWindow));
 155     Connect(CMD_TERMINATE,
 156             wxEVT_THREAD,
 157             wxThreadEventHandler(MyDllApp::OnTerminate));
 158 }
 159
 160 void MyDllApp::OnShowWindow(wxThreadEvent& event)
 161 {
 162     wxFrame *f = new MyDllFrame(NULL, event.GetString());
 163     f->Show(true);
 164 }
 165
 166 void MyDllApp::OnTerminate(wxThreadEvent& WXUNUSED(event))
 167 {
 168     ExitMainLoop();
 169 }
 170
 171
 172 // ----------------------------------------------------------------------------
 173 // application startup
 174 // ----------------------------------------------------------------------------
 175
 176 // we can't have WinMain() in a DLL and want to start the app ourselves
 177 IMPLEMENT_APP_NO_MAIN(MyDllApp)
 178
 179 namespace
 180 {
 181
 182 // Critical section that guards everything related to wxWidgets "main" thread
 183 // startup or shutdown.
 184 wxCriticalSection gs_wxStartupCS;
 185 // Handle of wx "main" thread if running, NULL otherwise
 186 HANDLE gs_wxMainThread = NULL;
 187
 188
 189 //  wx application startup code -- runs from its own thread
 190 unsigned wxSTDCALL MyAppLauncher(void* event)
 191 {
 192     // Note: The thread that called run_wx_gui_from_dll() holds gs_wxStartupCS
 193     //       at this point and won't release it until we signal it.
 194
 195     // We need to pass correct HINSTANCE to wxEntry() and the right value is
 196     // HINSTANCE of this DLL, not of the main .exe, use this MSW-specific wx
 197     // function to get it. Notice that under Windows XP and later the name is
 198     // not needed/used as we retrieve the DLL handle from an address inside it
 199     // but you do need to use the correct name for this code to work with older
 200     // systems as well.
 201     const HINSTANCE
 202         hInstance = wxDynamicLibrary::MSWGetModuleHandle("my_dll",
 203                                                          &gs_wxMainThread);
 204     if ( !hInstance )
 205         return 0; // failed to get DLL's handle
 206
 207     // IMPLEMENT_WXWIN_MAIN does this as the first thing
 208     wxDISABLE_DEBUG_SUPPORT();
 209
 210     // We do this before wxEntry() explicitly, even though wxEntry() would
 211     // do it too, so that we know when wx is initialized and can signal
 212     // run_wx_gui_from_dll() about it *before* starting the event loop.
 213     wxInitializer wxinit;
 214     if ( !wxinit.IsOk() )
 215         return 0; // failed to init wx
 216
 217     // Signal run_wx_gui_from_dll() that it can continue
 218     HANDLE hEvent = *(static_cast<HANDLE*>(event));
 219     if ( !SetEvent(hEvent) )
 220         return 0; // failed setting up the mutex
 221
 222     // Run the app:
 223     wxEntry(hInstance);
 224
 225     return 1;
 226 }
 227
 228 } // anonymous namespace
 229
 230 // ----------------------------------------------------------------------------
 231 // public DLL interface
 232 // ----------------------------------------------------------------------------
 233
 234 extern "C"
 235 {
 236
 237 void run_wx_gui_from_dll(const char *title)
 238 {
 239     // In order to prevent conflicts with hosting app's event loop, we
 240     // launch wx app from the DLL in its own thread.
 241     //
 242     // We can't even use wxInitializer: it initializes wxModules and one of
 243     // the modules it handles is wxThread's private module that remembers
 244     // ID of the main thread. But we need to fool wxWidgets into thinking that
 245     // the thread we are about to create now is the main thread, not the one
 246     // from which this function is called.
 247     //
 248     // Note that we cannot use wxThread here, because the wx library wasn't
 249     // initialized yet. wxCriticalSection is safe to use, though.
 250
 251     wxCriticalSectionLocker lock(gs_wxStartupCS);
 252
 253     if ( !gs_wxMainThread )
 254     {
 255         HANDLE hEvent = CreateEvent
 256                         (
 257                             NULL,  // default security attributes
 258                             FALSE, // auto-reset
 259                             FALSE, // initially non-signaled
 260                             NULL   // anonymous
 261                         );
 262         if ( !hEvent )
 263             return; // error
 264
 265         // NB: If your compiler doesn't have _beginthreadex(), use CreateThread()
 266         gs_wxMainThread = (HANDLE)_beginthreadex
 267                                   (
 268                                       NULL,           // default security
 269                                       0,              // default stack size
 270                                       &MyAppLauncher,
 271                                       &hEvent,        // arguments
 272                                       0,              // create running
 273                                       NULL
 274                                   );
 275
 276         if ( !gs_wxMainThread )
 277         {
 278             CloseHandle(hEvent);
 279             return; // error
 280         }
 281
 282         // Wait until MyAppLauncher signals us that wx was initialized. This
 283         // is because we use wxMessageQueue<> and wxString later and so must
 284         // be sure that they are in working state.
 285         WaitForSingleObject(hEvent, INFINITE);
 286         CloseHandle(hEvent);
 287     }
 288
 289     // Send a message to wx thread to show a new frame:
 290     wxThreadEvent *event =
 291         new wxThreadEvent(wxEVT_THREAD, CMD_SHOW_WINDOW);
 292     event->SetString(title);
 293     wxQueueEvent(wxApp::GetInstance(), event);
 294 }
 295
 296 void wx_dll_cleanup()
 297 {
 298     wxCriticalSectionLocker lock(gs_wxStartupCS);
 299
 300     if ( !gs_wxMainThread )
 301         return;
 302
 303     // If wx main thread is running, we need to stop it. To accomplish this,
 304     // send a message telling it to terminate the app.
 305     wxThreadEvent *event =
 306         new wxThreadEvent(wxEVT_THREAD, CMD_TERMINATE);
 307     wxQueueEvent(wxApp::GetInstance(), event);
 308
 309     // We must then wait for the thread to actually terminate.
 310     WaitForSingleObject(gs_wxMainThread, INFINITE);
 311     CloseHandle(gs_wxMainThread);
 312     gs_wxMainThread = NULL;
 313 }
 314
 315 } // extern "C"