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  1. Qt
  2. QTBUG-89118

style animated scroll bars might freeze(stop animating) if we do a heavy paint event

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    Details

    • Platform/s:
      All
    • Commits:
      04fed9f77e3288f69fe89bcb8a3f1cdbe02ce219 (qt/qtbase/dev) 01474c31ba2a3ca225cbc2440bd0ee28458b2a26 (qt/qtbase/6.0) b048faf869f16891034062d2b047c9c6c12e6b3e (qt/qtbase/5.15)

      Description

      #include <QtWidgets>
      #include <QScrollBar>
      
      class TextBrowser : public QTextBrowser
      {
      public:
          TextBrowser(QWidget *parent = 0) : QTextBrowser(parent)
          {
              for (int i = 0; i < 100; ++i)
                  append(QString(100, 'a'));
              findChild<QScrollBar *>()->installEventFilter(this);
          }
      
          bool eventFilter(QObject *obj, QEvent *event) override
          {
              if (qobject_cast<QScrollBar *>(obj) && event->type() == QEvent::Paint) {
                  QThread::currentThread()->msleep(1000);
              }
              return false;
          }
      };
      
      int main(int argc, char *argv[])
      {
          QApplication a(argc, argv);
          TextBrowser tb;
          tb.show();
          return a.exec();
      }
      

      Run this demo, and drag the scrollbar, you will find that the slider of scrollbar freezing during animation.

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        For Gerrit Dashboard: QTBUG-89118
        # Subject Branch Project Status CR V

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            Assignee:
            vhilshei Volker Hilsheimer
            Reporter:
            wang_chuan wang chuan
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              Dates

              Created:
              Updated:
              Resolved:

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