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  1. Qt
  2. QTBUG-121878

QQuickWindow::frameSwapped() never emitted with QQuickWidget::quickWindow()

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    • Icon: Bug Bug
    • Resolution: Invalid
    • Icon: P2: Important P2: Important
    • None
    • 6.6.1, 6.7.0 Beta2, 6.8
    • Quick: SceneGraph
    • None
    • Windows

      QQuickWidget's internal QQuickWindow object never emits QQuickWindow::frameSwapped() signal.

      Here's a code to compare:

      #include <QtQuickWidgets>
      
      int main(int argc, char **argv) {
          QApplication app{argc, argv};
      
          QQuickWidget w;
          w.setSource(QUrl{"qrc:/App/Main.qml"});
          w.resize(512, 512);
          w.show();
      
          QQuickView v;
          v.setSource(QUrl{"qrc:/App/Main.qml"});
          v.resize(512, 512);
          v.show();
      
          QObject::connect(w.quickWindow(), &QQuickWindow::frameSwapped, [] {
              qDebug() << "frameSwapped() from QQuickWidget::quickWindow()";
          });
          QObject::connect(&v, &QQuickWindow::frameSwapped, [] {
              qDebug() << "frameSwapped() from QQuickView";
          });
          return app.exec();
      }
      

      Main.qml is just BusyIndicator for continuous updating:

      import QtQuick.Controls.Material
      BusyIndicator {}
      

      Result:

      18:41:59: Starting D:\downloads\build-untitled19-Desktop_Qt_6_6_1_MSVC2019_64bit-Debug\appuntitled19.exe...
      QML debugging is enabled. Only use this in a safe environment.
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      frameSwapped() from QQuickView
      18:42:01: The process was ended forcefully.
      

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            janichol Andy Nichols
            bylee Byoung-young Lee
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              Created:
              Updated:
              Resolved:

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