EGLFS: OpenGL windows cannot be mixed with others.

[vasilim]

Running the example for qmloverlay in gstreamer gst-plugins-good repository.
It runs fine under X, but when running over EGLFS, fails with error:

EGLFS: OpenGL windows cannot be mixed with others.

main.cpp

#include <QApplication>
#include <QQmlApplicationEngine>
#include <QQuickWindow>
#include <QQuickItem>
#include <QRunnable>
#include <QDirIterator>
#include <gst/gst.h>

class SetPlaying : public QRunnable
{
public:
    SetPlaying(GstElement*);
    ~SetPlaying();

    void run();

private:
    GstElement* pipeline_;
};

SetPlaying::SetPlaying(GstElement* pipeline)
{
    this->pipeline_ = pipeline ? static_cast<GstElement*>(gst_object_ref(pipeline)) : NULL;
}

SetPlaying::~SetPlaying()
{
    if (this->pipeline_)
        gst_object_unref(this->pipeline_);
}

void SetPlaying::run()
{
    if (this->pipeline_)
        gst_element_set_state(this->pipeline_, GST_STATE_PLAYING);
}

static void on_overlay_scene_initialized(GstElement* overlay, gpointer unused)
{
    QQuickItem* rootObject;
    GST_INFO("scene initialized");
    g_object_get(overlay, "root-item", &rootObject, NULL);
    QQuickItem* videoItem = rootObject->findChild<QQuickItem*>("inputVideoItem");
    g_object_set(overlay, "widget", videoItem, NULL);
}

int main(int argc, char* argv[])
{
    int ret;

    gst_init(&argc, &argv);

    {
        QGuiApplication app(argc, argv);

        GstElement* pipeline = gst_pipeline_new(NULL);
        GstElement* src      = gst_element_factory_make("videotestsrc", NULL);
        GstElement* glupload = gst_element_factory_make("glupload", NULL);
        /* the plugin must be loaded before loading the qml file to register the
         * GstGLVideoItem qml item */
        GstElement* overlay  = gst_element_factory_make("qmlgloverlay", NULL);
        GstElement* overlay2 = gst_element_factory_make("qmlgloverlay", NULL);
        GstElement* sink     = gst_element_factory_make("qmlglsink", NULL);

        g_assert(src && glupload && overlay && sink);

        gst_bin_add_many(GST_BIN(pipeline), src, glupload, overlay, overlay2, sink, NULL);
        gst_element_link_many(src, glupload, overlay, overlay2, sink, NULL);

        /* load qmlglsink output */
        QQmlApplicationEngine engine;
        engine.load(QUrl(QStringLiteral("qrc:/main.qml")));

        QQuickItem*   videoItem;
        QQuickWindow* rootObject;

        /* find and set the videoItem on the sink */
        rootObject = static_cast<QQuickWindow*>(engine.rootObjects().first());
        videoItem  = rootObject->findChild<QQuickItem*>("videoItem");
        g_assert(videoItem);
        g_object_set(sink, "widget", videoItem, NULL);

        QDirIterator it(":", QDirIterator::Subdirectories);
        while (it.hasNext())
        {
            qDebug() << it.next();
        }

        QFile f(":/overlay.qml");
        if (!f.open(QIODevice::ReadOnly))
        {
            qWarning() << "error: " << f.errorString();
            return 1;
        }
        QByteArray overlay_scene = f.readAll();
        qDebug() << overlay_scene;

        QFile f2(":/overlay2.qml");
        if (!f2.open(QIODevice::ReadOnly))
        {
            qWarning() << "error: " << f2.errorString();
            return 1;
        }
        QByteArray overlay_scene2 = f2.readAll();
        qDebug() << overlay_scene2;

        /* load qmlgloverlay contents */
        g_signal_connect(
            overlay, "qml-scene-initialized", G_CALLBACK(on_overlay_scene_initialized), NULL);
        g_object_set(overlay, "qml-scene", overlay_scene.data(), NULL);

        g_signal_connect(
            overlay2, "qml-scene-initialized", G_CALLBACK(on_overlay_scene_initialized), NULL);
        g_object_set(overlay2, "qml-scene", overlay_scene2.data(), NULL);

        rootObject->scheduleRenderJob(
            new SetPlaying(pipeline), QQuickWindow::BeforeSynchronizingStage);

        ret = app.exec();

        gst_element_set_state(pipeline, GST_STATE_NULL);
        gst_object_unref(pipeline);
    }

    gst_deinit();

    return ret;
}

overlay.qml

#include <QApplication>
#include <QQmlApplicationEngine>
#include <QQuickWindow>
#include <QQuickItem>
#include <QRunnable>
#include <QDirIterator>
#include <gst/gst.h>

class SetPlaying : public QRunnable
{
public:
    SetPlaying(GstElement*);
    ~SetPlaying();

    void run();

private:
    GstElement* pipeline_;
};

SetPlaying::SetPlaying(GstElement* pipeline)
{
    this->pipeline_ = pipeline ? static_cast<GstElement*>(gst_object_ref(pipeline)) : NULL;
}

SetPlaying::~SetPlaying()
{
    if (this->pipeline_)
        gst_object_unref(this->pipeline_);
}

void SetPlaying::run()
{
    if (this->pipeline_)
        gst_element_set_state(this->pipeline_, GST_STATE_PLAYING);
}

static void on_overlay_scene_initialized(GstElement* overlay, gpointer unused)
{
    QQuickItem* rootObject;
    GST_INFO("scene initialized");
    g_object_get(overlay, "root-item", &rootObject, NULL);
    QQuickItem* videoItem = rootObject->findChild<QQuickItem*>("inputVideoItem");
    g_object_set(overlay, "widget", videoItem, NULL);
}

int main(int argc, char* argv[])
{
    int ret;

    gst_init(&argc, &argv);

    {
        QGuiApplication app(argc, argv);

        GstElement* pipeline = gst_pipeline_new(NULL);
        GstElement* src      = gst_element_factory_make("videotestsrc", NULL);
        GstElement* glupload = gst_element_factory_make("glupload", NULL);
        /* the plugin must be loaded before loading the qml file to register the
         * GstGLVideoItem qml item */
        GstElement* overlay  = gst_element_factory_make("qmlgloverlay", NULL);
        GstElement* overlay2 = gst_element_factory_make("qmlgloverlay", NULL);
        GstElement* sink     = gst_element_factory_make("qmlglsink", NULL);

        g_assert(src && glupload && overlay && sink);

        gst_bin_add_many(GST_BIN(pipeline), src, glupload, overlay, overlay2, sink, NULL);
        gst_element_link_many(src, glupload, overlay, overlay2, sink, NULL);

        /* load qmlglsink output */
        QQmlApplicationEngine engine;
        engine.load(QUrl(QStringLiteral("qrc:/main.qml")));

        QQuickItem*   videoItem;
        QQuickWindow* rootObject;

        /* find and set the videoItem on the sink */
        rootObject = static_cast<QQuickWindow*>(engine.rootObjects().first());
        videoItem  = rootObject->findChild<QQuickItem*>("videoItem");
        g_assert(videoItem);
        g_object_set(sink, "widget", videoItem, NULL);

        QDirIterator it(":", QDirIterator::Subdirectories);
        while (it.hasNext())
        {
            qDebug() << it.next();
        }

        QFile f(":/overlay.qml");
        if (!f.open(QIODevice::ReadOnly))
        {
            qWarning() << "error: " << f.errorString();
            return 1;
        }
        QByteArray overlay_scene = f.readAll();
        qDebug() << overlay_scene;

        QFile f2(":/overlay2.qml");
        if (!f2.open(QIODevice::ReadOnly))
        {
            qWarning() << "error: " << f2.errorString();
            return 1;
        }
        QByteArray overlay_scene2 = f2.readAll();
        qDebug() << overlay_scene2;

        /* load qmlgloverlay contents */
        g_signal_connect(
            overlay, "qml-scene-initialized", G_CALLBACK(on_overlay_scene_initialized), NULL);
        g_object_set(overlay, "qml-scene", overlay_scene.data(), NULL);

        g_signal_connect(
            overlay2, "qml-scene-initialized", G_CALLBACK(on_overlay_scene_initialized), NULL);
        g_object_set(overlay2, "qml-scene", overlay_scene2.data(), NULL);

        rootObject->scheduleRenderJob(
            new SetPlaying(pipeline), QQuickWindow::BeforeSynchronizingStage);

        ret = app.exec();

        gst_element_set_state(pipeline, GST_STATE_NULL);
        gst_object_unref(pipeline);
    }

    gst_deinit();

    return ret;
}

Similar code for overlay2.qml