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/frame.h"
  31 #include "wx/panel.h"
  32 #include "wx/sizer.h"
  33 #include "wx/stattext.h"
  34 #include "wx/button.h"
  35 #include "wx/thread.h"
  36 #include "wx/msgdlg.h"
  37 #include "wx/msw/wrapwin.h"
  38
  39 #include <process.h> // for _beginthreadex()
  40
  41 #include "my_dll.h"
  42
  43 // ----------------------------------------------------------------------------
  44 // GUI classes
  45 // ----------------------------------------------------------------------------
  46
  47 class MyDllFrame : public wxFrame
  48 {
  49 public:
  50     MyDllFrame(wxWindow *parent, const wxString& label);
  51
  52     void OnAbout(wxCommandEvent& event);
  53
  54     DECLARE_EVENT_TABLE()
  55 };
  56
  57
  58 static const int CMD_SHOW_WINDOW = wxNewId();
  59 static const int CMD_TERMINATE = wxNewId();
  60
  61 class MyDllApp : public wxApp
  62 {
  63 public:
  64     MyDllApp();
  65
  66 private:
  67     void OnShowWindow(wxThreadEvent& event);
  68     void OnTerminate(wxThreadEvent& event);
  69 };
  70
  71
  72 // ============================================================================
  73 // implementation
  74 // ============================================================================
  75
  76 // ----------------------------------------------------------------------------
  77 // MyDllFrame
  78 // ----------------------------------------------------------------------------
  79
  80 BEGIN_EVENT_TABLE(MyDllFrame, wxFrame)
  81     EVT_BUTTON(wxID_ABOUT, MyDllFrame::OnAbout)
  82 END_EVENT_TABLE()
  83
  84 MyDllFrame::MyDllFrame(wxWindow *parent, const wxString& label)
  85     : wxFrame(parent, wxID_ANY, label)
  86 {
  87     wxPanel *p = new wxPanel(this, wxID_ANY);
  88     wxSizer *sizer = new wxBoxSizer(wxVERTICAL);
  89
  90     sizer->Add
  91            (
  92                new wxStaticText
  93                    (
  94                        p, wxID_ANY,
  95                        wxString::Format
  96                        (
  97                            "Running using %s\n"
  98                            "wxApp instance is %p, thread ID %ld",
  99                            wxVERSION_STRING,
 100                            wxApp::GetInstance(),
 101                            wxThread::GetCurrentId()
 102                        )
 103                    ),
 104                wxSizerFlags(1).Expand().Border(wxALL, 10)
 105            );
 106
 107     sizer->Add
 108            (
 109                new wxButton(p, wxID_ABOUT, "Show info"),
 110                wxSizerFlags(0).Right().Border(wxALL, 10)
 111            );
 112
 113     p->SetSizerAndFit(sizer);
 114
 115     wxSizer *fsizer = new wxBoxSizer(wxVERTICAL);
 116     fsizer->Add(p, wxSizerFlags(1).Expand());
 117     SetSizerAndFit(fsizer);
 118 }
 119
 120 void MyDllFrame::OnAbout(wxCommandEvent& WXUNUSED(event))
 121 {
 122     wxMessageBox("This window is running in its own thread,\n"
 123                  "using private wxWidgets instance compiled into the DLL.",
 124                  "About",
 125                  wxOK | wxICON_INFORMATION);
 126 }
 127
 128
 129 // ----------------------------------------------------------------------------
 130 // MyDllApp
 131 // ----------------------------------------------------------------------------
 132
 133 MyDllApp::MyDllApp()
 134 {
 135     // Keep the wx "main" thread running even without windows. This greatly
 136     // simplifies threads handling, because we don't have to correctly
 137     // implement wx-thread restarting.
 138     //
 139     // Note that this only works if you don't explicitly call ExitMainLoop(),
 140     // except in reaction to wx_dll_cleanup()'s message. wx_dll_cleanup()
 141     // relies on the availability of wxApp instance and if the event loop
 142     // terminated, wxEntry() would return and wxApp instance would be
 143     // destroyed.
 144     //
 145     // Also note that this is efficient, because if there are no windows, the
 146     // thread will sleep waiting for a new event. We could safe some memory
 147     // by shutting the thread down when it's no longer needed, though.
 148     SetExitOnFrameDelete(false);
 149
 150     Connect(wxEVT_IDLE, wxIdleEventHandler(MyDllApp::OnIdle));
 151     Connect(CMD_SHOW_WINDOW,
 152             wxEVT_COMMAND_THREAD,
 153             wxThreadEventHandler(MyDllApp::OnShowWindow));
 154     Connect(CMD_TERMINATE,
 155             wxEVT_COMMAND_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 __stdcall unsigned 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.
 196     //
 197     // This method of obtaining DLL's instance handle requires at least
 198     // Windows XP/2003. We could also implement DllMain() and remember it from
 199     // there, that would work on older systems too.
 200     HINSTANCE hInstance;
 201     int ret = GetModuleHandleEx(GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS,
 202                                 (LPCTSTR)&MyAppLauncher,
 203                                 &hInstance);
 204     if ( ret == 0 )
 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" WXEXPORT
 235 void run_wx_gui_from_dll(const char *title)
 236 {
 237     // In order to prevent conflicts with hosting app's event loop, we
 238     // launch wx app from the DLL in its own thread.
 239     //
 240     // We can't even use wxInitializer: it initializes wxModules and one of
 241     // the modules it handles is wxThread's private module that remembers
 242     // ID of the main thread. But we need to fool wxWidgets into thinking that
 243     // the thread we are about to create now is the main thread, not the one
 244     // from which this function is called.
 245     //
 246     // Note that we cannot use wxThread here, because the wx library wasn't
 247     // initialized yet. wxCriticalSection is safe to use, though.
 248
 249     wxCriticalSectionLocker lock(gs_wxStartupCS);
 250
 251     if ( !gs_wxMainThread )
 252     {
 253         HANDLE hEvent = CreateEvent
 254                         (
 255                             NULL,  // default security attributes
 256                             FALSE, // auto-reset
 257                             FALSE, // initially non-signaled
 258                             NULL   // anonymous
 259                         );
 260         if ( !hEvent )
 261             return; // error
 262
 263         // NB: If your compiler doesn't have _beginthreadex(), use CreateThread()
 264         gs_wxMainThread = (HANDLE)_beginthreadex
 265                                   (
 266                                       NULL,           // default security
 267                                       0,              // default stack size
 268                                       &MyAppLauncher,
 269                                       &hEvent,        // arguments
 270                                       0,              // create running
 271                                       NULL
 272                                   );
 273
 274         if ( !gs_wxMainThread )
 275         {
 276             CloseHandle(hEvent);
 277             return; // error
 278         }
 279
 280         // Wait until MyAppLauncher signals us that wx was initialized. This
 281         // is because we use wxMessageQueue<> and wxString later and so must
 282         // be sure that they are in working state.
 283         WaitForSingleObject(hEvent, INFINITE);
 284         CloseHandle(hEvent);
 285     }
 286
 287     // Send a message to wx thread to show a new frame:
 288     wxThreadEvent *event =
 289         new wxThreadEvent(wxEVT_COMMAND_THREAD, CMD_SHOW_WINDOW);
 290     event->SetString(title);
 291     wxQueueEvent(wxApp::GetInstance(), event);
 292 }
 293
 294
 295 extern "C" WXEXPORT
 296 void wx_dll_cleanup(void)
 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_COMMAND_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 }