Preprocessor Macros to distinguish between Linux or Windows don't work ("no such slot")

Ninawe

Hi,
I have an application I want to get to work on Linux and on Windows 7 by using macros to decide which parts of the code to use. I have some slots and functions, that aren't needed on linux and vice versa.

Here is my minimal code:
Mainwindow. h
@#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QtGui>

class MainWindow : public QMainWindow
{
Q_OBJECT

public:

MainWindow(QWidget *parent = 0);
~MainWindow();

public slots:
#ifdef _WIN32
void onPushButtonClicked();
#endif
private:

 QPushButton* Pushbutton ;

};

#endif // MAINWINDOW_H
@
mainwindow.cpp
@
#include "mainwindow.h"
#include <QtGui>

MainWindow::MainWindow(QWidget parent)
: QMainWindow(parent)
{
QWidget mainWidget = new QWidget(this);
setCentralWidget(mainWidget);
QWidget* mainPage = new QWidget(mainWidget);
QVBoxLayout* mainLayout = new QVBoxLayout(mainPage);
Pushbutton = new QPushButton("Test",mainPage);
mainLayout->addWidget(Pushbutton);
mainPage->setLayout(mainLayout);
#ifdef _WIN32
connect (Pushbutton, SIGNAL(clicked()), this, SLOT(onPushButtonClicked()));
#endif
}

MainWindow::~MainWindow()
{

}
#ifdef _WIN32
void MainWindow::onPushButtonClicked()
{
Pushbutton->setStyleSheet("background-color: black");
}
#endif
@
Now the slot onPushButtonClicked() isn't found anymore:

Start ~\TestPreprocessor-build-Desktop-Debug\debug\TestPreprocessor.exe...Object::connect: No such slot MainWindow::onPushButtonClicked() in ..\TestPreprocessor\mainwindow.cpp:17

Only if I use my own defined macro or if I delete the #ifdef from the header file it works. But then I get a linker problem when compiling this on linux, as expected.

Can anyone tell me how to do this correctly?

SGaist

Hi,

Are you by any chance using Qt 4 ? If so, surrounding slots with ifdef won't work

Ninawe

Yes I am. Is there a work around?

SGaist

No there's not, however you can simply ifdef the content of the slot itself so it won't do anything on Linux.

Ninawe

Ok, thanks putting the #ifdef inside the function works. It's only problematic, if I have functions that take variables that are only defined by libraries existing in my linux project. For example keyboards, which I don't need for a desktop application in Windows...

Ninawe

Ok, thanks putting the #ifdef inside the function works. It's only problematic, if I have functions that take variables that are only defined by libraries existing in my linux project. For example keyboards, which I don't need for a desktop application in Windows...
@
#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QtGui>

class MainWindow : public QMainWindow
{
Q_OBJECT

public:
MainWindow(QWidget *parent = 0);
~MainWindow();
public slots:

void onPushButtonClicked();

private:
QPushButton* Pushbutton ;
};

#endif // MAINWINDOW_H
@
@
#include "mainwindow.h"
#include <QtGui>

MainWindow::MainWindow(QWidget parent)
: QMainWindow(parent)
{
QWidget mainWidget = new QWidget(this);
setCentralWidget(mainWidget);
// mainWidget->resize(800,480),setFixedSize(sizeHint());

QWidget* mainPage = new QWidget(mainWidget);
QVBoxLayout* mainLayout = new QVBoxLayout(mainPage);
Pushbutton = new QPushButton("Test",mainPage);
mainLayout->addWidget(Pushbutton);
mainPage->setLayout(mainLayout);

#ifdef _WIN32
connect (Pushbutton, SIGNAL(clicked()), this, SLOT(onPushButtonClicked()));
#endif
}

MainWindow::~MainWindow()
{

}

void MainWindow::onPushButtonClicked()
{
#ifdef _WIN32
Pushbutton->setStyleSheet("background-color: black");
#endif
}
@

SGaist

Why would function parameters have something to do there ? Can you show an example ?

Ninawe

I have a linux application running on a AM335x of Texas Instruments, which has no keyboard. So I use some Keyboard wrappers provided by another department at my firm. These libraries are only for Linux, so I #ifdef them in the header. But if I would like to use them as a variable in a function, it wouldn't be known to the compiler, see the example here:
@
#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QtGui>
#ifdef unix
#include "Keyboards/keyboards.h"
#endif
class MainWindow : public QMainWindow
{
Q_OBJECT

public:
MainWindow(QWidget *parent = 0);
~MainWindow();
public slots:

void onPushButtonClicked();
void useKeyboard(EnglishKeyboard testKeyboard2); // <----------------

private:
QPushButton* Pushbutton ;
#ifdef unix
EnglishKeyboard testKeyboard;
#endif
};

#endif // MAINWINDOW_H
@

@
#include "mainwindow.h"
#include <QtGui>

MainWindow::MainWindow(QWidget parent)
: QMainWindow(parent)
{
QWidget mainWidget = new QWidget(this);
setCentralWidget(mainWidget);
// mainWidget->resize(800,480),setFixedSize(sizeHint());

QWidget* mainPage = new QWidget(mainWidget);
QVBoxLayout* mainLayout = new QVBoxLayout(mainPage);
Pushbutton = new QPushButton("Test",mainPage);
mainLayout->addWidget(Pushbutton);
mainPage->setLayout(mainLayout);

#ifdef _WIN32
connect (Pushbutton, SIGNAL(clicked()), this, SLOT(onPushButtonClicked()));
#endif
}

MainWindow::~MainWindow()
{

}

void MainWindow::useKeyboard(EnglishKeyboard testKeyboard2)
{
testKeyboard2;
}

void MainWindow::onPushButtonClicked()
{
#ifdef _WIN32
Pushbutton->setStyleSheet("background-color: black");
#endif
}

@

SGaist

You should rather use the Q_OS_XXX macros from Qt.

You can either ifdef things like you are currently doing, or you could consider using the PIMPL idiom and thus only compile the right private part depending on the platform.