QML Scene does not reliably start

I see that when it does work, there is a lot of garbage in the Application Output window. The first few blocks that end with "/usr/lib/x86_64-linux-gnu/qt5/bin/qmlscene exited with code 0" are runs where the window did not load properly. The one with all the GLib warnings was a run where the window *did* load.

Starting /usr/lib/x86_64-linux-gnu/qt5/bin/qmlscene -I /home/rick/Projects/SoundBoard -I /usr/bin -I /usr/lib/x86_64-linux-gnu/qt5/qml /home/rick/Projects/SoundBoard/SoundBoard.qml
QQmlComponent: Component is not ready
/usr/lib/x86_64-linux-gnu/qt5/bin/qmlscene exited with code 0

Starting /usr/lib/x86_64-linux-gnu/qt5/bin/qmlscene -I /home/rick/Projects/SoundBoard -I /usr/bin -I /usr/lib/x86_64-linux-gnu/qt5/qml /home/rick/Projects/SoundBoard/SoundBoard.qml
QQmlComponent: Component is not ready
/usr/lib/x86_64-linux-gnu/qt5/bin/qmlscene exited with code 0

Starting /usr/lib/x86_64-linux-gnu/qt5/bin/qmlscene -I /home/rick/Projects/SoundBoard -I /usr/bin -I /usr/lib/x86_64-linux-gnu/qt5/qml /home/rick/Projects/SoundBoard/SoundBoard.qml
QQmlComponent: Component is not ready
/usr/lib/x86_64-linux-gnu/qt5/bin/qmlscene exited with code 0

Starting /usr/lib/x86_64-linux-gnu/qt5/bin/qmlscene -I /home/rick/Projects/SoundBoard -I /usr/bin -I /usr/lib/x86_64-linux-gnu/qt5/qml /home/rick/Projects/SoundBoard/SoundBoard.qml
QQmlComponent: Component is not ready

(qmlscene:13042): GLib-GObject-WARNING **: cannot register existing type `GIOCondition'

(qmlscene:13042): GLib-GObject-WARNING **: /build/buildd/glib2.0-2.36.0/./gobject/gtype.c:4239: type id `0' is invalid

(qmlscene:13042): GLib-GObject-WARNING **: can't peek value table for type `<invalid>' which is not currently referenced

(qmlscene:13042): GLib-GObject-WARNING **: /build/buildd/glib2.0-2.36.0/./gobject/gvalue.c:190: cannot initialize GValue with type `(null)', this type has no GTypeValueTable implementation

(qmlscene:13042): GLib-GObject-CRITICAL **: g_value_set_flags: assertion `G_VALUE_HOLDS_FLAGS (value)' failed

(qmlscene:13042): GLib-GObject-CRITICAL **: g_value_unset: assertion `G_IS_VALUE (value)' failed

(qmlscene:13042): GLib-GObject-WARNING **: cannot register existing type `GIOCondition'

(qmlscene:13042): GLib-GObject-WARNING **: /build/buildd/glib2.0-2.36.0/./gobject/gtype.c:4239: type id `0' is invalid

(qmlscene:13042): GLib-GObject-WARNING **: can't peek value table for type `<invalid>' which is not currently referenced

(qmlscene:13042): GLib-GObject-WARNING **: /build/buildd/glib2.0-2.36.0/./gobject/gvalue.c:190: cannot initialize GValue with type `(null)', this type has no GTypeValueTable implementation

(qmlscene:13042): GLib-GObject-CRITICAL **: g_value_set_flags: assertion `G_VALUE_HOLDS_FLAGS (value)' failed

(qmlscene:13042): GLib-GObject-CRITICAL **: g_value_unset: assertion `G_IS_VALUE (value)' failed

(qmlscene:13042): GLib-GObject-WARNING **: cannot register existing type `GIOCondition'

(qmlscene:13042): GLib-GObject-WARNING **: /build/buildd/glib2.0-2.36.0/./gobject/gtype.c:4239: type id `0' is invalid

(qmlscene:13042): GLib-GObject-WARNING **: can't peek value table for type `<invalid>' which is not currently referenced

(qmlscene:13042): GLib-GObject...

jp can you please reproduce this

I am unable to reproduce with our application templates. However it looks similar to https://bugs.launchpad.net/ubuntu-qtcreator-plugins/+bug/1179920 "[QtCreator] Extraneous windows with garbage content"

I think that I am experiencing this too, but it looks like some compiz issue, at least it consumes a lot of cpu and the whole unity is slow. Do you see high cpu usage for compiz when this happens?

Could you paste the result of following:
apt-cache policy libqt5core5

I’m seeing the same issue.

osomon@granuja:~$ LANGUAGE=C apt-cache policy libqt5core5
libqt5core5:
  Installed: 5.0.2+dfsg1-3ubuntu1~raring1~test2
  Candidate: 5.0.2+dfsg1-3ubuntu1~raring1~test2
  Version table:
 *** 5.0.2+dfsg1-3ubuntu1~raring1~test2 0
        500 http://ppa.launchpad.net/canonical-qt5-edgers/qt5-proper/ubuntu/ raring/main amd64 Packages
        100 /var/lib/dpkg/status
     5.0.1+dfsg-0ubuntu4 0
        500 http://fr.archive.ubuntu.com/ubuntu/ raring/main amd64 Packages

I am not sure if this is the same bug, but some times I don't see anything in the window, but instead of restarting, only resizing the window makes it work. (qt 5.0.1)

Looks like resizing the window does, in fact, make it work.

I've observed this bug in the QML support for Go as well, and FYI I've worked around it in Qt 5.0.2 by sending a resize event right after showing the Window, along the lines of:

    struct ShowWindow : public QQuickWindow {
        void show() {
            QQuickWindow::show();
            QResizeEvent resize(size(), size());
            resizeEvent(&resize);
        }
    };

This Window reliably shows every time.

I've added a note to the bug description pointing out that this is not specific to Qt Creator or the qmlscene binary. This problem has been observed with custom QML applications linking directly against Qt as well.

Can anyone reproduce this bug?

Seems none can reproduce this anymore.