Question

I am using the combination mentioned in the title while trying to run the window layout example from the qt tutorials. The main looks like this:

#include <QtGui>

int main(int argc, char **argv) {
  QApplication app(argc, argv);
  QWidget window;
  QLabel *label = new QLabel(QApplication::translate("windowlayout", "Name:"));
  QLineEdit *lineEdit = new QLineEdit();

  QHBoxLayout *layout = new QHBoxLayout();
  layout->addWidget(label);
  layout->addWidget(lineEdit);
  window.setLayout(layout);
  window.setWindowTitle(
      QApplication::translate("windowlayout", "Window layout"));
  window.show();
  return app.exec();
}

And the CMakeLists.txt like this:

PROJECT(test)
CMAKE_MINIMUM_REQUIRED(VERSION 2.8.0)

FIND_PACKAGE(Qt4 REQUIRED)
INCLUDE_DIRECTORIES(${QT_INCLUDE_DIR} ${QT_QTCORE_INCLUDE_DIR} ${QT_QTGUI_INCLUDE_DIR})

SET(test_SRCS main.cc)

QT4_AUTOMOC(${test_SRCS})

ADD_EXECUTABLE(test ${test_SRCS})

TARGET_LINK_LIBRARIES(test ${QT_QTGUI_LIBRARIES} ${QT_QTCORE_LIBRARIES})

The building and compilation work properly but when I run the application, it always show a command prompt. How do I avoid that?

Answer 1

In your CMakeFile with Qt4, you don’t need to change your CPP code or to add flags at compile time. Simply use

set(QT_USE_QTMAIN TRUE)

It will automatically link qtmain.lib with your executable. This library defines other common main() signatures, including WinMain().

With this trick, your app can compile with MSVC under Windows, without mofiying your original main() function and without displaying a console when you run your app outside of your IDE (QtCreator for example).

Final resulting CMakeLists.txt can be :

PROJECT(test)
CMAKE_MINIMUM_REQUIRED(VERSION 2.8.0)

FIND_PACKAGE(Qt4 REQUIRED)
if(WIN32)
    SET(QT_USE_QTMAIN TRUE)
endif(WIN32)

INCLUDE(${QT_USE_FILE})

SET(test_SRCS main.cc)

QT4_AUTOMOC(${test_SRCS})

ADD_EXECUTABLE(test ${test_SRCS})

TARGET_LINK_LIBRARIES(test ${QT_LIBRARIES})

Additionnaly, you don’t need to include QtCore and QtGui, they are included by default with QT_USE_FILE (for include folders) and QT_LIBRARIES (for libraries).

You only have to set what modules you use, or you don’t use (for Gui) :

# Use Network and Sql modules
set(QT_USE_QTNETWORK TRUE)
set(QT_USE_QTSQL TRUE)
# Do not use Gui module
set(QT_DONT_USE_QTGUI TRUE)