compiling under qt4 AND qt5

In Qt 4.x, one typically needs to #include <QtGui>, and in Qt 5.x much of the stuff there is moved to <QtWidgets>

What are the recommended ifdefs needed in c++ source code and .pro -files in order to have a project compile under both Qt4 and Qt5 ?

Quote:

---

Originally Posted by drhex

In Qt 4.x, one typically needs to #include <QtGui>, and in Qt 5.x much of the stuff there is moved to <QtWidgets>

---

Actually you should never use the two above because this significatly increases compile time. You should always include just the classes you need

Quote:

---

What are the recommended ifdefs needed in c++ source code and .pro -files in order to have a project compile under both Qt4 and Qt5 ?

---

Code:

---

#if QT_VERSION >= 0x050000
// Qt5 code
#else
// Qt4 code
#endif

---

Code:

---

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

---

It appears one needs to

Code:

---

#include <qglobal.h>

---

first, or else QT_VERSION won't be defined.

If you take wysota's advice about individual class #includes there will usually be no reason to #ifdef between Qt4 and Qt5 in your code. Even if there is a need for version based code the first #include <QApplication>, <QWidget> etc. will have brought qglobal.h in anyway.

This:

Code:

---

#include <QApplication>
#include <QMainWindow>
#include <QTableView>

---

not this

Code:

---

#include "qglobal.h"
#if QT_VERSION >= 0x050000
// Qt5 code
#include <QtWidgets>
#else
// Qt4 code
#include <QtGui>
#endif

---

The entry in the PRO file is needed either way.