Using SFML in a resizable QT-Widget

[RoberTwoD]

Hi,

I'm new to SFML and QT, so I tryed out the SFML Tutorial "Integration of SFML in QT Interface" with X11 (on Ubuntu/Linux).
This actually worked well for a static QSFMLCanvas, which size doesnt change.
But when I resize the "QSFMLCanvas", the underlying sf::RenderWindow does not do the same.
It keeps its old values for width and height.
I did not change the code of the example, please help me...

[RoberTwoD]

Or in other words. How can I use SFML in a QWidget with dynamic size...

[Grimshaw]

Firstly, the sf::RenderWindow should always fit the client area of the widget.

That means the rect that can draw things, coincides with the widget's rect, except for some possible border/margin.

Since the sf::RenderWindow took an external window handle, it should work as a proxy for the real window(the qt widget), meaning that if the widget resizes, its slave RenderWindow should get the Resize event too!

Once you catch that event, you just need to act acordingly, which normally means configuring the view for the new size!

Hope it helps!

[iforce2d]

I'm using the latest snapshot of 2.0 and can't get this to work either. In a normal standalone window in the main message loop it works great with glViewport and sf::RenderWindow::SetView, like this:

Code: [Select]

if (event.Type == sf::Event::Resized) {
    glViewport(0, 0, event.Size.Width, event.Size.Height);
    window.SetView( sf::View( sf::FloatRect(0,0,window.GetWidth(),window.GetHeight()) ) );
}
So I figured that when the resize event comes from the Qt widget, you would do the same, like this:

Code: [Select]

void QSFMLCanvas::resizeEvent( QResizeEvent * event )
{
    int newWidth = event->size().width();
    int newHeight = event->size().height();

    glViewport( 0, 0, newWidth, newHeight );
    SetView( sf::View( sf::FloatRect(0,0,newWidth, newHeight) ) );

    QWidget::resizeEvent(event);
}
But it seems that the extent of the drawn region does not change. Here is what it looks like when the application first starts:



... and this is after resizing the window a little. It looks like the RenderWindow itself is filling the widget correctly because the green background from the Clear() is there, but the stuff that I am drawing never gets out of the original region it started in.



I discovered that I can use sf::RenderWindow::SetViewport to get what I want, but this is a bit inconvenient because it seems to require the ratio to the original window dimensions. For example, if my widget's starting dimensions are 149x115, this will work ok:

Code: [Select]

   sf::View newView(sf::FloatRect(0,0,newWidth, newHeight) );
    newView.SetViewport( sf::FloatRect( 0,0, newWidth / 149.f, newHeight / 115.f ) );
    SetView( newView );

and gives me the behavior I want:



... but it seems unusually inconvenient for SFML where everything else is easy
Am I missing something?

[iforce2d]

Okay, I discovered something else. I can put the same code I had in the main message loop of the standalone app, into the OnUpdate() function of the widget, like this:

Code: [Select]

void MyCanvas::OnUpdate()
{
    sf::Event event;
    while ( PollEvent(event) )
    {
        if ( event.Type == sf::Event::Resized ) {
            glViewport(0, 0, event.Size.Width, event.Size.Height);
            SetView( sf::View( sf::FloatRect(0,0,m_GetWidth,m_GetHeight) ) );
        }

        // ... check mouse and keys etc
    }
}

Maybe this is bad practice, I don't know. But it works ok so far and I like it because I can use almost the exact same code when I detach this from the Qt framework.
If anybody has any reason why this may be bad please let me know