[Qt-interest] QWidget update() function not calling paintEvent()

[YoBro]

Hi all!
   Sorry I am reposting since the formatting got messed up when I cut and pasted last time. I realize others 
have had this problem too; but I haven't found a fix to mine yet. I was 
playing around with some code from the Qt tutorial and I am stuck 
because one of my QWidget inherited classes calls update(QRegion&) 
but it does not trigger a call to paintEvent(..) - essentially I am 
trying to do a simple refactoring of the tutorial source code to add 
multiple shots using a CannonShot class in the 12th chapter of the Qt 
tutorial (see the link: http://doc.trolltech.com/4.3/tutorial-t12.html)

The CannonField update() still works correctly and causes its paintEvent
 re-implementation to be called. Its only CannonShot's update() that 
does not call its own paintEvent. (I've confirmed that it does get 
before and after the update call). Here are some snippets:

CannonField class:
-----------------------------------------------

#ifndef CANNONFIELD_H
#define CANNONFIELD_H

#include <QWidget>
class QTimer;
class CannonShot;

class CannonField : public QWidget
{
   Q_OBJECT

public:
   CannonField(QWidget *parent = 0);
   ~CannonField();
   static int angle() { return currentAngle; }
   static int force() { return currentForce; }

public slots:
   void setAngle(int angle);
   void setForce(int force);
   void shoot();

signals:
   void angleChanged(int newAngle);
   void forceChanged(int newForce);

protected:
   void paintEvent(QPaintEvent *event);

public:
   static int currentAngle;
   static int currentForce;

private:
    //-Vector of shots
   QVector<CannonShot*> shots;

    void paintCannon(QPainter& painter, QColor& color);
};

#endif

CannonField source:
------------------------------------

#include "cannonfield.h"
#include "cannonshot.h"

int CannonField::currentAngle = 45;
int CannonField::currentForce = 0;

CannonField::CannonField(QWidget *parent): QWidget(parent)
{
    setPalette(QPalette(QColor(250, 250, 200)));
   setAutoFillBackground(true);
 }

CannonField::~CannonField() {
   //-Delete all allocated shots
   for(int i=0; i < shots.size(); ++i) {
      if(shots[i]) {
         delete shots[i];
         shots[i] = NULL;
      }
   }
   shots.clear();
}

void CannonField::shoot()
{
   shots.push_back(new CannonShot(this));
   (shots.back())->shoot();
}

void CannonField::paintEvent(QPaintEvent * /* event */)
{
   QPainter painter(this);
   QColor color;

   //-Update the widget for all shots currently on the field
   bool no_shots_plots_active = true;
   for(QVector<CannonShot*>::const_iterator itr = shots.begin(); itr != shots.end(); ++itr) {
      if ((*itr)->shotTimer()->isActive()) {
         (*itr)->paintShot(painter);
         color = Qt::red;
         paintCannon(painter, color);
         no_shots_plots_active = false;
      }
      else if ((*itr)->plotTimer()->isActive()) {
         (*itr)->paintShotTrajectory(painter);
         color = Qt::blue;
         paintCannon(painter, color);
         no_shots_plots_active = false;
      }
   }
   if(no_shots_plots_active) {
      color = Qt::blue;
      paintCannon(painter, color);
   }
}

CannonShot class:
----------------------------
#ifndef CANNONSHOT_H
#define CANNONSHOT_H

#include <QWidget>
#include <QMap>
class QTimer;
class QSignalMapper;

class CannonShot : public QWidget
{
   Q_OBJECT

public:
   CannonShot(QWidget *parent = 0);
   int angle() const { return shotAngle; }
   int force() const { return shotForce; }
   QTimer* shotTimer() {return autoShotTimer;}
   void shoot();
   QRect shotRect() const;
   void paintShot(QPainter&);
 
private slots:
   void moveShot();

signals:
   void angleChanged(int);
   void forceChanged(int);

protected:
   void paintEvent(QPaintEvent *event);

private:
   QVector<QRect> shotRects() const;
  
   int shotTimerCount;
   QTimer* autoShotTimer;
   float shotAngle;
   float shotForce;
};

#endif

CannonShot source:
-------------------------------

#include "cannonshot.h"

CannonShot::CannonShot(QWidget *parent): QWidget(parent)
{
   setPalette(QPalette(QColor(250, 250, 200)));
   setAutoFillBackground(true);
   shotTimerCount = 0;
   autoShotTimer = new QTimer(this);
   connect(autoShotTimer, SIGNAL(timeout()), this, SLOT(moveShot()));
}

void CannonShot::shoot()
{
   if (autoShotTimer->isActive())
      return;
   shotTimerCount = 0;
   shotAngle = angle();
   shotForce = force();
   autoShotTimer->start(5);
}

void CannonShot::moveShot()
{
    QRegion region = shotRect();
   ++shotTimerCount;

   QRect shotR = shotRect();
   if (shotR.x() > width() || shotR.y() > height()) {
       autoShotTimer->stop();
       emit missed();
   }
   else {
       region = region.unite(shotR);
   }

   //-These fail to call paintEvent even though code passes this point as I checked.
   update(region);
   //repaint(region);
}

void CannonShot::paintEvent(QPaintEvent * /* event */)
{
   //-Never gets here!!
   QPainter painter(this);
   QColor color;
   //-Do whatever
}

Driver app:
-------------------

#include "cannonfield.h"
#include "lcdrange.h"

class MyWidget : public QWidget
{
public:
   MyWidget(QWidget *parent = 0);
};

MyWidget::MyWidget(QWidget *parent)
   : QWidget(parent)
{
   QPushButton *quit = new QPushButton(tr("&Quit"));
   quit->setFont(QFont("Times", 18, QFont::Bold));

   connect(quit, SIGNAL(clicked()), qApp, SLOT(quit()));

   LCDRange *angle = new LCDRange(tr("&ANGLE"));
    angle->setRange(0, 90);

   LCDRange *force = new LCDRange(tr("&FORCE"));
   force->setRange(10, 50);

   //CannonField *cannonField = new CannonField;
   CannonField *cannonField = new CannonField(this);

   connect(angle, SIGNAL(valueChanged(int)),
           cannonField, SLOT(setAngle(int)));
   connect(cannonField, SIGNAL(angleChanged(int)),
           angle, SLOT(setValue(int)));

   connect(force, SIGNAL(valueChanged(int)),
           cannonField, SLOT(setForce(int)));
   connect(cannonField, SIGNAL(forceChanged(int)),
           force, SLOT(setValue(int)));

   QPushButton *shoot = new QPushButton(tr("&Shoot"));
   shoot->setFont(QFont("Times", 18, QFont::Bold));
   connect(shoot, SIGNAL(clicked()), cannonField, SLOT(shoot()));

   //-Other layout stuff..

int main(int argc, char *argv[])
{
   QApplication app(argc, argv);
   MyWidget widget;
   widget.setMinimumSize(300, 300);
   widget.setSizePolicy(QSizePolicy::Fixed, QSizePolicy::Fixed);
   widget.setGeometry(100, 100, 500, 355);
   widget.show();
   return app.exec();
}

Again, sorry for the repost.. thanks to anyone who has read and responded. Any ideas are 
appreciated!

--T.


 
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