Qt, OpenGL Widget, no such slot - c++

Question

I wanted to create a simple application where there's triangle generated using OpenGL and three push buttons changing that triangle color. The triangle is generated but unfortunately buttons don't work and I get errors saying:
QObject::connect: No such slot MainWindow::redSlot(OGL) in
..\buttonwidget\mainwindow.cpp:17 QObject::connect: No such slot
MainWindow::greenSlot(OGL) in ..\buttonwidget\mainwindow.cpp:20
QObject::connect: No such slot MainWindow::blueSlot(OGL) in
..\buttonwidget\mainwindow.cpp:23
I have slots definitions:
void MainWindow::redSlot(Widget* w)
{
w->setColor(red);
}
void MainWindow::greenSlot(Widget* w)
{
w->setColor(green);
}
void MainWindow::blueSlot(Widget* w)
{
w->setColor(blue);
}
They are changing variable declared in class Widget that changes color of a generated triangle. Here's class Widget:
class Widget : public QGLWidget
{
Q_OBJECT
public:
Widget(QWidget *parent = 0);
QSize minimumSizeHint() const;
QSize sizeHint() const;
enum color c;
void setColor(enum color color1);
protected:
void initializeGL();
void paintGL();
void resizeGL(int width, int height);
};
And then I connect slots to buttons in class MainWindow constructor:
MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent)
{
layout = new QVBoxLayout();
QWidget *w = new QWidget();
setCentralWidget(w);
w->setLayout(layout);
Widget *OGL = new Widget();
//OGL->c=green; - it was a test whether changing value of enum type variable c works
//it works, changing it changes the color of a generated triangle
redButton = new QPushButton(tr("Red"));
connect(redButton, SIGNAL(clicked()), this, SLOT(redSlot(OGL)));
greenButton = new QPushButton(tr("Green"));
connect(greenButton, SIGNAL(clicked()), this, SLOT(greenSlot(OGL)));
blueButton = new QPushButton(tr("Blue"));
connect(blueButton, SIGNAL(clicked()), this, SLOT(blueSlot(OGL)));
layout->addWidget(OGL);
layout->addWidget(redButton);
layout->addWidget(greenButton);
layout->addWidget(blueButton);
}
Here's slot declaration in header:
class MainWindow : public QMainWindow
{
Q_OBJECT
QVBoxLayout *layout;
public:
MainWindow(QWidget *parent = 0);
~MainWindow();
private:
QPushButton *redButton;
QPushButton *greenButton;
QPushButton *blueButton;
public slots:
void redSlot(Widget*);
void greenSlot(Widget*);
void blueSlot(Widget*);
};
How should I make them work?

Answer 1

Connects in QT are string-based, that means:
connect(redButton, SIGNAL(clicked()), this, SLOT(redSlot(OGL)));
will not work, since you havent defined a slot "redSlot(OGL)", instead you would have to use
...SLOT(redSlot(Widget*)));
Moreover, it is possible to define a SLOT with less parameter but not with more, therefore your slot/connect has to look like
void redSlot();
connect(redButton, SIGNAL(clicked()), this, SLOT(redSlot()));
if you need a pointer to the "Widget" you have to retrieve it from somewhere else.
Example: Define slot in "Widget"-class and change connect to:
connect(redButton, SIGNAL(clicked()), OGL, SLOT(redSlot()));