When you run the program with the debugger attached, it will appear in the Visual Studio output window, but for debugging purposes, I often redirect the debug output to some nice log window that you can do using the qInstallMsgHandler function:
The code I'm using is:
#include <qapplication.h> #include <qwidget.h> #include <qplaintextedit.h> #include <qmetaobject.h> #include <qthread.h> #include <qboxlayout.h> #include <qdatetime.h> #include <qdebug.h> #include <cstdio> #include <cassert> QWidget *DEBUG_MESSAGE_DISPLAY_WIDGET = NULL; QPlainTextEdit *DEBUG_MESSAGE_DISPLAY_TEXTEDIT = NULL; void setupDebugDisplay(); void debugMessageDisplayFunc(QtMsgType type, const char *msg); int main( int argc, char* argv[] ) { QApplication a( argc, argv ); a.setQuitOnLastWindowClosed( true ); setupDebugDisplay(); // your code here.... eg: // YourMainWindow mainWindow; int ret = a.exec(); delete DEBUG_MESSAGE_DISPLAY_WIDGET; return ret; } void setupDebugDisplay() { QWidget *widget = new QWidget(); widget->setWindowTitle( "Debug Log" ); widget->setAttribute( Qt::WA_QuitOnClose, false ); //quit only when mainwindow is closed QBoxLayout* layout = new QVBoxLayout(); widget->setLayout( layout ); QPlainTextEdit *textEdit = new QPlainTextEdit( widget ); QFont font = QFont( "Monospace" ); font.setStyleHint(QFont::TypeWriter); textEdit->setFont( font ); textEdit->setReadOnly(true); layout->addWidget( textEdit ); widget->show(); DEBUG_MESSAGE_DISPLAY_WIDGET = widget; DEBUG_MESSAGE_DISPLAY_TEXTEDIT = textEdit; qInstallMsgHandler(debugMessageDisplayFunc); } void debugMessageDisplayFunc(QtMsgType type, const char *msg) { bool do_abort = false; const char* msgTypeStr = NULL; switch (type) { case QtDebugMsg: msgTypeStr = "Debug"; break; case QtWarningMsg: msgTypeStr = "Warning"; break; case QtCriticalMsg: msgTypeStr = "Critical"; break; case QtFatalMsg: msgTypeStr = "Fatal"; do_abort = true; default: assert(0); return; } QTime now = QTime::currentTime(); QString formattedMessage = QString::fromLatin1("%1 %2 %3") .arg(now.toString("hh:mm:ss:zzz")) .arg(msgTypeStr).arg(msg); // print on console: fprintf( stderr, "%s\n", formattedMessage.toLocal8Bit().constData() ); // print in debug log window { bool isMainThread = QThread::currentThread() == QApplication::instance()->thread(); if(DEBUG_MESSAGE_DISPLAY_TEXTEDIT) { if( isMainThread ) DEBUG_MESSAGE_DISPLAY_TEXTEDIT->appendPlainText( formattedMessage ); else // additional code, so that qDebug calls in threads will work aswell QMetaObject::invokeMethod( DEBUG_MESSAGE_DISPLAY_TEXTEDIT, "appendPlainText", Qt::QueuedConnection, Q_ARG( QString, formattedMessage ) ); } } }