QGraphicsScene QPainterPath::arcTo: Adding arc where a parameter is NaN, results are undefined

[kiepmad]

Hello,

I just started out with QT and have a problem that I can't seem to solve.
I'm working on Nine Men's Morris and the everything works great, except for a strange bug that creeps up.

Sometimes, when I click on a Item the GraphicsView turns white and the following error is shown several times in the debug window:

QPainterPath::arcTo: Adding arc where a parameter is NaN, results are undefined

The GraphicsView cannot be recovered by resizing, etc., only by restarting the game.

I've created a MainWindow and with a QGraphicsView and a QGraphicsScene.

I created 3 seperate QGraphicsItems

1. A boardLayout which renders the background and does not handle click events.
2. A Token Item that handles click events, the color of the token, if it's selected, etc.
3. A BoardPosition Item that is invisible and handles the events when you click on an empty position on the board. Clicking this item causes the error described above.

MainWindow Code:
@
ui->setupUi(this);
this->setWindowIcon(QPixmap(QString(":/Images/icon2.jpeg")));

showWin = new WinDialog(this);
startWindow = new StartDialog(this);

view = new QGraphicsView(this);
this->setCentralWidget (view);

view->setVerticalScrollBarPolicy (Qt::ScrollBarAlwaysOff);
view->setHorizontalScrollBarPolicy (Qt::ScrollBarAlwaysOff);
view->setMinimumSize (1000, 800);
view->setViewportUpdateMode (QGraphicsView::FullViewportUpdate);
view->setCacheMode (QGraphicsView::CacheNone);
view->setRenderHints (QPainter::Antialiasing |  QPainter::TextAntialiasing);

scene = NULL;

//this->debugWidget = new DebugWidget(this);
//this->debugWidget->setMinimumWidth (200);

this->layout = NULL;
this->controller = NULL;

this->whiteTokensSet = 0;
this->blackTokensSet = 0;

}

void MainWindow::Initalize()
{
scene = new QGraphicsScene();
scene->setBackgroundBrush (QBrush(Qt::gray));
view->setScene (scene);
this->layout = new BoardLayout();
scene->addItem(layout);

float x = 0.081f;
float y = 0.025f;
for(int i = 0; i < 7; i++)
{
    text.append(scene->addText(QString('A'+i)));
    text.at(i)->setX(x+(i*0.13));
    text.at(i)->setY(y - 0.008);
    text.at(i)->setScale(0.003);
}
x = 0.072f;
for(int i = 7; i < 14; i++)
{
    text.append(scene->addText(QString('1'+(i-7))));
    text.at(i)->setX(y);
    text.at(i)->setY(x+((i-7)*0.13));
    text.at(i)->setScale(0.003);
}

this->controller = new GameController(this);

view->fitInView (layout, Qt::KeepAspectRatio);

points[0] = QPointF(0.085f, 0.085f);
points[1] = QPointF(0.475f, 0.085f);
points[2] = QPointF(0.865f, 0.085f);
points[3] = QPointF(0.215f, 0.215f);
points[4] = QPointF(0.475f, 0.215f);
points[5] = QPointF(0.735f, 0.215f);
points[6] = QPointF(0.345f, 0.345f);
points[7] = QPointF(0.475f, 0.345f);
points[8] = QPointF(0.605f, 0.345f);
points[9] = QPointF(0.085f, 0.475f);
points[10] = QPointF(0.215f, 0.475f);
points[11] = QPointF(0.345f, 0.475f);
points[12] = QPointF(0.605f, 0.475f);
points[13] = QPointF(0.735f, 0.475f);
points[14] = QPointF(0.865f, 0.475f);
points[15] = QPointF(0.345f, 0.605f);
points[16] = QPointF(0.475f, 0.605f);
points[17] = QPointF(0.605f, 0.605f);
points[18] = QPointF(0.215f, 0.735f);
points[19] = QPointF(0.475f, 0.735f);
points[20] = QPointF(0.735f, 0.735f);
points[21] = QPointF(0.085f, 0.865f);
points[22] = QPointF(0.475f, 0.865f);
points[23] = QPointF(0.865f, 0.865f);

for(int i = 0; i < 24; i++)
{
    boardPositions.append (new BoardPosition(i, points[i].x(), points[i].y(), this->controller));
    this->scene->addItem(boardPositions.at (i));
}

whiteTokensSet = 0;
blackTokensSet = 0;

for(int i = 0; i < 9; i++)
{
    whiteTokens.append(new GameToken(WHITE, this->controller));
    whiteTokens.at(i)->setVisible(false);
    this->scene->addItem(whiteTokens.at(i));
    blackTokens.append(new GameToken(BLACK, this->controller));
    blackTokens.at(i)->setVisible(false);
    this->scene->addItem(blackTokens.at(i));
}

this->startWindow->close ();
//this->debugWidget->appendText(QString("Welcome to Nine Men's Morris!"));
//this->addDockWidget(Qt::LeftDockWidgetArea, this->debugWidget);
this->show();
this->resize(QSize(1001, 801));

}
@
BoardPositions Code:
@
#include "boardposition.h"
#include "gamecontroller.h"

BoardPosition::BoardPosition(int pos, float coordx, float coordy, GameController *controller) :
QGraphicsItem()
{
boardPos = pos;
posx = coordx;
posy = coordy;
this->controller = controller;
}

QRectF BoardPosition::boundingRect() const
{
return QRectF(posx, posy, 0.05, 0.05);
}

void BoardPosition::paint(QPainter *painter, const QStyleOptionGraphicsItem *option,
QWidget *widget)
{
painter->setPen(Qt::NoPen);
painter->setBrush(Qt::transparent);

painter->drawRect(QRectF(posx, posy, 0.05, 0.05));

}

void BoardPosition::mousePressEvent(QGraphicsSceneMouseEvent *event)
{
controller->boardClicked(boardPos);

}
@

How could I debug this error, or did I do something entirely wrong?

Please let me know if you need any other information. (You can cownload the whole code here: https://www.dropbox.com/s/osc7l2tyxf63qp6/nine-mens-morris-ff306f393749.zip )

[koahnig]

welcome to devnet

What OS, compiler, IDE, etc are you using?
When you are running the application in the debugger, are you getting an exception?

[kiepmad]

Thanks!

I'm using Ubuntu 12.04 x64, Qt-Creator and the gcc that comes with latest ubuntu (4.6 I believe)

However the same occurs when using Windows7 with Qt-Creator and Visual C++ compiler.

I don't get any exceptions.

[koahnig]

Since you do not get exceptions, how do you know that you are introducing nan then?