More qt-peer issues

[hs4233 at mail.mn-solutions.de (Holger Schurig)]

> -------------------------------------------------------------------
> QFont: It is not safe to use text and fonts outside the gui thread
> -------------------------------------------------------------------
>
> See my earlier mail,
> http://developer.classpath.org/pipermail/classpath/2006-February/000069.htm
>l

Hmm, it might be the case that this is really some weird interoperability 
between pthread's usage of Qt, the VM and Classpath.

First a look at the function that creates this warning, in 


// from src/gui/text/qfont.cpp:
void qt_font_tread_test()
{
    if (QApplication::instance() && QThread::currentThread()
     != QApplication::instance()->thread())
        qWarning("QFont: It is not safe to use text and fonts outside \
                  the gui thread");
}


This function get's called in two of the four QFont constructors. 
QApplication::instance() returns the QApplication object or NULL. 
QThread::currentThread() is defined as a static method like this:


// from src/corelib/thread/qthread_unix.cpp:
QThread *QThread::currentThread()
{
    pthread_once(&current_thread_key_once, create_current_thread_key);
    return reinterpret_cast<QThread *>
        (pthread_getspecific(current_thread_key));
}

This means that some thread id is stored in the per-thread specific area of 
each thread and that Qt just safely casts this to a QThread pointer.



QApplication::instance()->thread() just points is to the thread() method of 
the QObject:


// src/corelib/kernel/qobject.cpp
QThread *QObject::thread() const
{ return QThreadPrivate::threadForId(d_func()->thread); }


But here my knowledge is at the end. I've no knowledge about the internals of 
Qt's d_func or QThreadPrivate.


When I augment the qt_font_tread_test() from above and let a mini AWT app run, 
then I see:

Java_gnu_java_awt_peer_qt_QtFontPeer_create: (nil) QThread::currentThread()
Java_gnu_java_awt_peer_qt_QtFontPeer_create: 0x8093618 
QApplication::instance()->thread()
QFont: It is not safe to use text and fonts outside the gui thread
Java_gnu_java_awt_peer_qt_QtFontPeer_create: (nil) QThread::currentThread()
Java_gnu_java_awt_peer_qt_QtFontPeer_create: 0x8093618 
QApplication::instance()->thread()
QFont: It is not safe to use text and fonts outside the gui thread
Java_gnu_java_awt_peer_qt_QtFontPeer_create: (nil) QThread::currentThread()
Java_gnu_java_awt_peer_qt_QtFontPeer_create: 0x8093618 
QApplication::instance()->thread()
QFont: It is not safe to use text and fonts outside the gui thread
Java_gnu_java_awt_peer_qt_QtFontPeer_create: (nil) QThread::currentThread()
Java_gnu_java_awt_peer_qt_QtFontPeer_create: 0x8093618 
QApplication::instance()->thread()
QFont: It is not safe to use text and fonts outside the gui thread
QWidget::setMinimumSize: The smallest allowed size is (0,0)
Java_gnu_java_awt_peer_qt_QtFontPeer_create: (nil) QThread::currentThread()
Java_gnu_java_awt_peer_qt_QtFontPeer_create: 0x8093618 
QApplication::instance()->thread()
QFont: It is not safe to use text and fonts outside the gui thread
QWidget::setMinimumSize: The smallest allowed size is (0,0)
Java_gnu_java_awt_peer_qt_QtFontPeer_create: (nil) QThread::currentThread()
Java_gnu_java_awt_peer_qt_QtFontPeer_create: 0x8093618 
QApplication::instance()->thread()
QFont: It is not safe to use text and fonts outside the gui thread
Java_gnu_java_awt_peer_qt_QtFontPeer_create: (nil) QThread::currentThread()
Java_gnu_java_awt_peer_qt_QtFontPeer_create: 0x8093618 
QApplication::instance()->thread()
QFont: It is not safe to use text and fonts outside the gui thread
Java_gnu_java_awt_peer_qt_QtFontPeer_create: 0x8093618 
QThread::currentThread()
Java_gnu_java_awt_peer_qt_QtFontPeer_create: 0x8093618 
QApplication::instance()->thread()
Java_gnu_java_awt_peer_qt_QtFontPeer_create: 0x8093618 
QThread::currentThread()
Java_gnu_java_awt_peer_qt_QtFontPeer_create: 0x8093618 
QApplication::instance()->thread()
Java_gnu_java_awt_peer_qt_QtFontPeer_create: 0x8093618 
QThread::currentThread()
Java_gnu_java_awt_peer_qt_QtFontPeer_create: 0x8093618 
QApplication::instance()->thread()
Java_gnu_java_awt_peer_qt_QtFontPeer_create: 0x8093618 
QThread::currentThread()
Java_gnu_java_awt_peer_qt_QtFontPeer_create: 0x8093618 
QApplication::instance()->thread()

Now, what to make out of this info?