clicked() signal in a button - qt

Question

I've got some problem with signal for a button in Qt 4.8.0. I am using vs 2010 with Qt Designer. I have created a button in Designer with playButton name. But after that I tried to connect clicked() signal (in vs) with my function from CRenderArea (to start a timer), but it seems that it doesn't work (the function start() works when I put it in the constructor, so it's not the problem of the code itself). The code is compiling, the program is executing, but after clicking a button - nothing happens (it should move a line).
I would be really thankful for some help, just started a fun with Qt.
The codes are here (I hope the number of files won't scare you, these are the simplest codes ever :) ):
main.cpp
#include "ts_simulator.h"
#include <QtGui/QApplication>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
TS_simulator w;
w.show();
return a.exec();
}
ts_simulator.cpp:
TS_simulator::TS_simulator(QWidget *parent, Qt::WFlags flags)
: QMainWindow(parent, flags)
{
p_map = new CRenderArea();
ui.setupUi( this );
p_map->setParent( ui.renderArea );
// this doesn't work, why?
connect( ui.playButton, SIGNAL( clicked() ), this, SLOT( p_map->start() ) );
}
CRenderArea.h
#pragma once
#include <QtGui>
class CRenderArea : public QWidget {
Q_OBJECT // I think it's necessary?
int x;
QBasicTimer* timer;
public:
CRenderArea();
public slots: // this is necessary too, right?
void start();
private:
void timerEvent( QTimerEvent* );
void paintEvent( QPaintEvent* );
};
and CRenderArea.cpp:
#include "CRenderArea.h"
CRenderArea::CRenderArea() : x( 0 ) {
setBackgroundRole( QPalette::Base );
setMinimumSize( 591, 561 );
setAutoFillBackground( true );
timer = new QBasicTimer();
}
void CRenderArea::timerEvent( QTimerEvent* e ) {
++x;
update();
}
void CRenderArea::paintEvent( QPaintEvent* p ) {
QPainter painter(this);
painter.setRenderHint(QPainter::Antialiasing);
painter.setPen(Qt::darkGray);
painter.drawLine(2+x/10, 8, 60, 300);
}
void CRenderArea::start() {
timer->start( 0, this );
}
Greets.

Answer 1

The problem is here:
connect( ui.playButton, SIGNAL( clicked() ), this, SLOT( p_map->start() ) );
if p_map is the receiver of the signal, and it has Q_OBJECT, it should be written as:
connect( ui.playButton, SIGNAL( clicked() ), p_map, SLOT(start()) );