[PyQt] Resize flicking on QMainWindow centralWidget in python but not C++

[Patrick Stinson]

So it does, and changing that makes it work like the C++ example.

My own app is still showing the problem even without using QOpenGLWidget. I wonder if there is some setting somewhere that implicitly uses QOpenGLWidget….

> On Oct 5, 2019, at 5:36 PM, Eric Pettersen <pett at cgl.ucsf.edu> wrote:
> 
> Your Python class inherits from QOpenGLWidget.  Your C++ class inherits from QWidget.
> 
>> On Oct 5, 2019, at 2:10 PM, Patrick Stinson <patrickkidd at gmail.com <mailto:patrickkidd at gmail.com>> wrote:
>> 
>> Hello,
>> 
>> On MacOS, a QMainWindow with a simple painted centralWidget flickers when resizing quickly in python but not in C++. This only occurs with QMainWindow It is particularly pronounced more complex widgets, as shown in the following video:
>> 
>> https://youtu.be/0Qjy2wm6m9M <https://youtu.be/0Qjy2wm6m9M>
>> 
>> Here is the python example that shows the bug. Just run, rapidly resize the height of the widget , and observe a black flickering on the top edge of the widget as the height changes.
>> 
>> class Widget(QOpenGLWidget):
>>     def paintEvent(self, e):
>>         p = QPainter(self)
>>         p.setBrush(Qt.red)
>>         p.drawRect(self.rect())
>> 
>> app = QApplication(sys.argv)
>> mw = QMainWindow()
>> w = Widget()
>> mw.setCentralWidget(w)
>> mw.show()
>> w.show()
>> app.exec()
>> 
>> 
>> The following 1-to-1 C++ translation shows no such behavior:
>> 
>> 
>> #include <QApplication>
>> #include <QMainWindow>
>> #include <QWidget>
>> #include <QPainter>
>> 
>> class Widget : public QWidget {
>> public:
>>     void paintEvent(QPaintEvent *) {
>>         QPainter p(this);
>>         p.setBrush(Qt::red);
>>         p.drawRect(rect());
>>     }
>> };
>> 
>> int main(int argc, char *argv[])
>> {
>>     QApplication a(argc, argv);
>>     QMainWindow mw;
>>     QWidget *w = new Widget;
>>     mw.setCentralWidget(w);
>>     mw.show();
>>     return a.exec();
>> }
>> 
>> 
>> 
>> 
>> 
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