An issue when rendering a line depending on Mouse position - c++

Question

I have an openGL widget, where I want to render a line which is dependent of mouse positions, as follows:
glPushMatrix();
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glColor4f(1, 0, 0, 0.1);
glScalef(a, b, 0);
glBegin(GL_LINES);
glVertex2f(pushedX, pushedY);
glVertex2f(currentX, currentY);
glEnd();
glFlush();
glDisable(GL_BLEND);
glPopMatrix();
where:
pushedX=buttonPressCoordinates.x();
pushedY=buttonPressCoordinates.y();
currentX=mouseCurrentPosition.x();
currentY=mouseCurrentPosition.y();
The rendering goes good, and the line is rendered as required when I move the mouse connecting with line the pushed and current coordinates.
BUT:
the issue is, that even when I press my mouse somewhere on the widget and don't move it, it generates randomly (as I think) some (x,y) and connects the it with a line with the coordinates of mouse pressed position. Though when I start moving my mouse it starts working fine.
Please, help to fix this bug.
EDIT
The code of assigning the current values of the mouse
void MainWindow::mouseMoveEvent(QMouseEvent *eventMove)
{
if(eventMove->buttons() & Qt::LeftButton)
{
GLWidget *widget = this->findChild<GLWidget *>("glwidget");
float x = widget->getNormalizedWidth(widget->mapFromGlobal(QCursor::pos()).x());
float y = widget->getNormalizedHeight(widget->mapFromGlobal(QCursor::pos()).y());
float y_ = 1.0 - y;
mouseCurrentPosition.setX(x);
mouseCurrentPosition.setY(y_);
widget->setCurrentX(mouseCurrentPosition.x());
widget->setCurrentY(mouseCurrentPosition.y());
}
}
note: QPointF mouseCurrentPosition;, getNormalizedWidth(...) is my defined fundction which works perfect.
EDIT-2
The mouse click coordinates are updated as follows:
setMouseTracking(true);
m = true;
GLWidget *widget = this->findChild<GLWidget *>("glwidget");
float x = widget->getNormalizedWidth(widget->mapFromGlobal(QCursor::pos()).x());
float y = widget->getNormalizedHeight(widget->mapFromGlobal(QCursor::pos()).y());
float y_ = 1.0 - y;
buttonPressCoordinates.setX(x);
buttonPressCoordinates.setY(y_);
qDebug() << buttonPressCoordinates.x() << buttonPressCoordinates.y();
widget->setQ(true);
widget->setPushedX(buttonPressCoordinates.x());
widget->setPushedY(buttonPressCoordinates.y());

Answer 1

One thing you can try is to update currentX and currentY in the mouseMoveEvent when LeftButton is not pressed:
void MainWindow::mouseMoveEvent(QMouseEvent *eventMove)
{
GLWidget *widget = this->findChild<GLWidget *>("glwidget");
float x = widget->getNormalizedWidth(widget->mapFromGlobal(QCursor::pos()).x());
float y = widget->getNormalizedHeight(widget->mapFromGlobal(QCursor::pos()).y());
float y_ = 1.0 - y;
if(eventMove->buttons() & Qt::LeftButton)
{
buttonPressCoordinates.setX(x);
buttonPressCoordinates.setY(y_);
widget->setPushedX(buttonPressCoordinates.x());
widget->setPushedY(buttonPressCoordinates.y());
}
else
{
mouseCurrentPosition.setX(x);
mouseCurrentPosition.setY(y_);
widget->setCurrentX(mouseCurrentPosition.x());
widget->setCurrentY(mouseCurrentPosition.y());
}
}