Qt 4.8.4 - Problem generating click - coordinates used by QPoint

[portegael]

Hello guys,

I am working on an embedded linux project using Qt 4.8.4 and I want to generate click to a given position.

First I will give you a sum-up of my code and then explains the problem.

main.cpp : Declare a new QApplication

@int main( int argc, char *argv[] )
{
main_app = new QApplication( argc, argv ) ;

[....]

}@

mainwindow.h : header of the mainwindow

@class MainWindow : public QMainWindow
{
Q_OBJECT

public :

void generate_click( int coord_x, int coord_y ) ;

[...]
}@

mainwindow.cpp: definition of my function

@void MainWindow::generate_click(int x, int y)
{

printf("Enter generate_click : (%d/%d)\n", x, y) ;

QPoint _pos_click( x, y ) ;
QWidget *receiver = QApplication::widgetAt( _pos_click ) ;

if(receiver == 0)
printf("No element at the position (%d, %d)\n", x, y) ;
else
{
QMouseEvent *event = new QMouseEvent(QEvent::MouseButtonPress, receiver->mapFromGlobal(_pos_click), Qt::LeftButton, Qt::LeftButton, Qt::NoModifier);
main_app->postEvent(receiver, event);
QMouseEvent *release = new QMouseEvent(QEvent::MouseButtonRelease, receiver->mapFromGlobal(_pos_click), Qt::LeftButton, Qt::LeftButton,Qt::NoModifier);
main_app->postEvent(receiver, release);
}
}@

This way it is NOT working, even if the coordinates are good in my first printf. I never see the error "receiver == 0 ). If we modify the Qt library to add a log in the function PostEvent we see that x or y (randomly) equal 0 or 1 so that's why there is no click.

If I modify x and y this way (give a value to x / y ) it WORKS all the time :

@void MainWindow::generate_click(int x, int y)
{

x = 20 ;
y = 80 ;

printf("Enter generate_click : (%d/%d)\n", x, y) ;

QPoint _pos_click( x, y ) ;
QWidget *receiver = QApplication::widgetAt( _pos_click ) ;

if(receiver == 0)
printf("No element at the position (%d, %d)\n", x, y) ;
else
{
QMouseEvent *event = new QMouseEvent(QEvent::MouseButtonPress, receiver->mapFromGlobal(_pos_click), Qt::LeftButton, Qt::LeftButton, Qt::NoModifier);
main_app->postEvent(receiver, event);
QMouseEvent *release = new QMouseEvent(QEvent::MouseButtonRelease, receiver->mapFromGlobal(_pos_click), Qt::LeftButton, Qt::LeftButton,Qt::NoModifier);
main_app->postEvent(receiver, release);
}
}@

If I add an addition to the coordinate I receive, it also WORKS !

@void MainWindow::generate_click(int x, int y)
{

x = x + 5;
y = y + 5;

printf("Enter generate_click : (%d/%d)\n", x, y) ;

QPoint _pos_click( x, y ) ;
QWidget *receiver = QApplication::widgetAt( _pos_click ) ;

if(receiver == 0)
printf("No element at the position (%d, %d)\n", x, y) ;
else
{
QMouseEvent *event = new QMouseEvent(QEvent::MouseButtonPress, receiver->mapFromGlobal(_pos_click), Qt::LeftButton, Qt::LeftButton, Qt::NoModifier);
main_app->postEvent(receiver, event);
QMouseEvent *release = new QMouseEvent(QEvent::MouseButtonRelease, receiver->mapFromGlobal(_pos_click), Qt::LeftButton, Qt::LeftButton,Qt::NoModifier);
main_app->postEvent(receiver, release);
}
}@

Even if the Qt documentation says that QPoint is expecting an integer, I think that the addition or the fact that we give fixed coordinates will cast them in a type expected by QPoint.

Are you able to tell me why the first example is not working ?

I hope my problem is clear and let me know if you need more information.
Thanks in advance.

Gaël