Widgets are not updated - is this a bug?

[Jeremy Katz]

On 24/Jun/20 23:46, Christian ARNAUD wrote:
> Hi,
> 
>  
> 
> I ran in a strange behavior where widgets in the view aren’t properly
> refreshed on change.
> 
> Here is the code, developed to show the problem:
> 
[ code omitted ]  
> 
> If the pushbutton is clicked with the mouse or with the space key (after
> getting the focus with Tab), the text in the lineedit is not refreshed.
> If a repaint is forced, it is.
> 
> If the pushbutton is clicked with the enter key (after getting the focus
> with Tab), the text in the lineedit is correctly refreshed.
> 
>  
> 
> Any idea?
> 
>  
> 
> My env:
> 
> OSX Catalina 10.15.5
> Python 3.6
> PyQt: 15.0
> 

I'm having similar issues with macOS 10.15.6, Python 3.6.3, Qt 5.15.0,
and PyQt 5.15.0. This doesn't appear to be an issue on Windows 10 or
Linux/X11, and doesn't occur on the same version of macOS with a nearly
identical C++ program.

The QTextEdit is correctly painted as soon as focus is transferred to
another window via mouse click, command-tab, etc. Scheduling the
operation that eventually leads to a repaint for the next iteration of
the event loop also works.

import sys
import PyQt5.QtWidgets as W
import PyQt5.QtCore as C

app = W.QApplication(sys.argv)
w = W.QWidget()
layout = W.QVBoxLayout()
edit = W.QTextEdit()
edit.setText(C.qVersion())

button = W.QPushButton("broken")
button.clicked.connect(edit.clear)

button2 = W.QPushButton("not broken")
button2.clicked.connect(lambda: C.QMetaObject.invokeMethod(edit,
"clear", C.Qt.QueuedConnection))

layout.addWidget(button)
layout.addWidget(button2)
layout.addWidget(edit)
w.setLayout(layout)
w.show()
app.exec_()