[Qt-interest] stdout of MSWin GUI application run from console

[Michael Jackson]

I am probably going to miss the subtle difference here but can't you just
set the "SUBSYSTEM" to "CONSOLE" instead of "WINDOWS" in the Visual Studio
Project? This makes the GUI app also pop up an console window when launched
although it is a separate console window so maybe the is the difference.

Just my 2 cents. I do like the code though.

Mike Jackson
http://www.bluequartz.net

On 4/13/11 10:35 PM, in article 4DA65D68.6010608 at argyllcms.com, "Graeme
Gill" wrote:

> For those interested, here's the current state of this code as an
> add-on to main(). Probably better to create a library function
> in the long term if you want to use this approach.
> 
> Also attached is a patch for Qt 4.7.2 to fix this behaviour in Qt itself,
> so that no extra application code is needed, and there is then better
> similarity
> of cross platform behaviour.
> 
> Graeme Gill.
> 
> -------------------------------------------------------------------
> #include <QApplication>
> #include <stdio.h>
> #include "tdialog.hpp"
> 
> #ifdef Q_WS_WIN
> #include <windows.h>
> 
> void winConsoleMsgHandler(QtMsgType t, const char* str) {
>          fprintf(stderr, "%s\n", str);
>          fflush(stderr);
> }
> #endif // Q_WS_WIN
> 
> int main(int argc, char *argv[]) {
> 
> #ifdef Q_WS_WIN
>      {
>          BOOL (WINAPI *AttachConsole)(DWORD dwProcessId);
> 
>          AttachConsole = (BOOL (WINAPI*)(DWORD))
>              GetProcAddress(LoadLibraryA("kernel32.dll"), "AttachConsole");
> 
>              if (AttachConsole != NULL && AttachConsole(((DWORD)-1))) {
>                  if (_fileno(stdout) == -1)
>                      freopen("CONOUT$","wb",stdout);
>                  if (_fileno(stderr) == -1)
>                      freopen("CONOUT$","wb",stderr);
>                  if (_fileno(stdin) == -1)
>                      freopen("CONIN$","rb",stdin);
> 
>                  // Fix C++
>                  std::ios::sync_with_stdio();
> 
>                  // Fix messages
>                  qInstallMsgHandler(winConsoleMsgHandler);
>              }
>      }
> #endif // Q_WS_WIN
> 
>      printf("This is stdout\n");
>      fprintf(stderr,"This is stderr\n");
>      qDebug("This is a qDebug message");
> 
>      QApplication app(argc, argv);
>      TDialog *dialog = new TDialog;
>      dialog->show();
> 
>      qDebug("This is another qDebug message");
> 
>      return app.exec();
> }
> 
> -------------------------------------------------------------------
> *** src/corelib/kernel/qcoreapplication_win.cpp Thu Apr 14 11:17:48 2011
> --- src/corelib/kernel/qcoreapplication_win.cpp Thu Apr 14 12:14:09 2011
> *************** void qWinMain(HINSTANCE instance, HINSTA
> *** 181,191 ****
>            qWarning("Qt: Internal error: qWinMain should be called only
> once");
>            return;
>        }
>        already_called = true;
> -     usingWinMain = true;
> 
> !     // Install default debug handler
> !     qInstallMsgHandler(qWinMsgHandler);
> 
>        // Create command line
>        argv = qWinCmdLine<char>(cmdParam, int(strlen(cmdParam)), argc);
> --- 181,214 ----
>            qWarning("Qt: Internal error: qWinMain should be called only
> once");
>            return;
>        }
> +
>        already_called = true;
> 
> ! #ifdef Q_WS_WIN
> !   // Re-attach stdio if application was started from a console
> !   BOOL (WINAPI *pAttachConsole)(DWORD dwProcessId);
> !
> !   pAttachConsole = (BOOL (WINAPI*)(DWORD))
> !       GetProcAddress(LoadLibraryA("kernel32.dll"), "AttachConsole");
> !
> !   if (pAttachConsole != NULL && pAttachConsole(((DWORD)-1))) {
> !       if (_fileno(stdout) == -1)
> !           freopen("CONOUT$","wb",stdout);
> !       if (_fileno(stderr) == -1)
> !           freopen("CONOUT$","wb",stderr);
> !       if (_fileno(stdin) == -1)
> !           freopen("CONIN$","rb",stdin);
> !
> !       // Fix C++
> !       std::ios::sync_with_stdio();
> !   } else
> ! #endif // Q_WS_WIN
> !   {
> !       usingWinMain = true;    // Reset to qWinMsgHandler on
> qInstallMsgHandler(0)
> !
> !       // Install default debug handler
> !       qInstallMsgHandler(qWinMsgHandler);
> !   }
> 
>        // Create command line
>        argv = qWinCmdLine<char>(cmdParam, int(strlen(cmdParam)), argc);