Two different methods of using QBrush with QPainter - why is only one working?

[wysota]

To add to that -- if you keep the brush as a member variable, then setting the brush on the painter with setBrush() does not increase memory use -- you have two "handles" to the brush but in fact only one instance of brush data. This works as long as you don't modify any of the "handles". If you do then a copy takes place so that each brush has its own instance of data. But since you modify the brush to apply the changes right away, you end up with a single instance of data again as the old data is deleted by QBrush. Same works for QPen, of course.

[EMKAH]

Thank you both for your valuable answers!

Greetings,
Markus

[EMKAH]

Hello again!

As I'm advancing with my little widget, i just got another problem, which is also related with widget painting, so i decided to append my new problem right here in order to not flood the forum.

I have subclassed my ProgressPie widget to create a timer-controlled progress pie. You give it a range and it counts down or up its limit values. I did this by implementing QObject::startTimer() and the timerEvent() method.

I simply wanted to use my setValue() method from the parent widget which already includes a request to redraw itself after a value change:

repaint(this->rect());

repaint(this->rect());

To copy to clipboard, switch view to plain text mode 

But when I call the function from the timerEvent() subclassed widged, nothing happens - unless i resize the window, which will trigger the resizeEvent (which is also implemented in the parent's code and which contains just the same line of code).

When i put the line directly into my timerEvent() method of the subclass, the widget will repaint itself properly every time the timerEvent occurs.
So - why's that?

This is the whole code of both functions:

The setValue() method of the parent class:

void QtProgressPie::setValue(const int &val)
{
    // Sets the given value which is checked against its bounds
    if (val != _value)
    {
        _value = qBound(_minimum, val, _maximum);
        repaint(this->rect());
    }
}

void QtProgressPie::setValue(const int &val)
{
    // Sets the given value which is checked against its bounds
    if (val != _value)
    {
        _value = qBound(_minimum, val, _maximum);
        repaint(this->rect());
    }
}

To copy to clipboard, switch view to plain text mode 

The timerEvent() of the subclass:

void QtTimedProgressPie::timerEvent(QTimerEvent *e)
{
    // Modifies the current value of the timed ProgressPie.
    // By calling setValue of QtProgressPie, the widget will also be approprietely redrawn. // <--- No, it will not! :-(
    // Also, if the minimum or maximum value is arrived, the timerEvent will kill the timer
    // and emit the finished()-signal.
 
    if (_countBackwards)    // First case: counting towards _minimum
    {
        this->setValue(--_value);   // dec and set value
        if (_value == _minimum)     // check if value is now equal to the minimum
        {                           // if yes, kill timer and emit signal
            _timerIsRunning = false;
            killTimer(e->timerId());
            emit finished();
        }
    }
    else                    // Second case: counting towards _maximum
    {
        this->setValue(++_value);   // inc and set value
        if (_value == _maximum)     // check if value is now equal to the maximum
        {                           // if yes, kill timer and emit signal
            _timerIsRunning = false;
            killTimer(e->timerId());
            emit finished();
        }
    }
    repaint(this->rect()); // <--- this seems to be needed, but why?
}

void QtTimedProgressPie::timerEvent(QTimerEvent *e)
{
    // Modifies the current value of the timed ProgressPie.
    // By calling setValue of QtProgressPie, the widget will also be approprietely redrawn. // <--- No, it will not! :-(
    // Also, if the minimum or maximum value is arrived, the timerEvent will kill the timer
    // and emit the finished()-signal.

    if (_countBackwards)    // First case: counting towards _minimum
    {
        this->setValue(--_value);   // dec and set value
        if (_value == _minimum)     // check if value is now equal to the minimum
        {                           // if yes, kill timer and emit signal
            _timerIsRunning = false;
            killTimer(e->timerId());
            emit finished();
        }
    }
    else                    // Second case: counting towards _maximum
    {
        this->setValue(++_value);   // inc and set value
        if (_value == _maximum)     // check if value is now equal to the maximum
        {                           // if yes, kill timer and emit signal
            _timerIsRunning = false;
            killTimer(e->timerId());
            emit finished();
        }
    }
    repaint(this->rect()); // <--- this seems to be needed, but why?
}

To copy to clipboard, switch view to plain text mode 

EDIT: typo

[wysota]

First of all use update() instead of repaint(). Second of all you don't have to pass rect() into the call as by default the widget updates its whole rect. Third of all the call that you mark as needed is not needed.

[EMKAH]

Thanks for your advice. I adapted the code according to your remarks, but I still need the call inside the timerEvent() method, otherwise the widget won't get updated.


EDIT: i finally got it. Thie problem was not the update() call but the way I called the setValue()-method.

I tried to call setValue() with ++_value or --_value. This of course manipulates _value directly before calling the method with the same new _value.

But my setValue() method begins with a check if the given integer parameter is different to the actual _value (because I want to emit a valueChanged() signal from that method). Of course, this will never be true, because of the direct manipulation of _value with ++ and --.

Anyway, thanks for you help!