Widgets are not updated - is this a bug?

[Phil Thompson]

On 17/09/2020 13:04, Raymond Osborn wrote:
> The repaint issue has been a problem on Macs for a couple of years
> affecting PyQt5 since v5.11 at least. I am still on Mac OS 10.14. Here
> is a link to a Qt Forum post in 2018 -
> https://forum.qt.io/topic/98059/push-button-label-settext-not-refreshing-under-macos
> <https://forum.qt.io/topic/98059/push-button-label-settext-not-refreshing-under-macos>.
> I’m not sure if it affected Mac OS 10,13. It doesn’t affect PyQt 5.9.
> I have had to subclass most of the PyQt5 widgets that I use to add a
> repaint whenever they are updated programmatically.
> 
> Ray

To clarify, it's not the version of PyQt that is the problem, it is the 
version of Qt that PyQt is built against that is the problem.

Phil


>> On Sep 17, 2020, at 4:12 AM, Phil Thompson 
>> <phil at riverbankcomputing.com> wrote:
>> 
>> On 17/09/2020 09:46, Jeremy Katz wrote:
>>> On 17/Sep/20 01:08, Jeremy Katz wrote:
>>>> On 15/Sep/20 06:29, Phil Thompson wrote:
>>>> [...]
>>>>> However I am currently at a loss about what is happening. I am 
>>>>> using a
>>>>> version of PyQt that only uses "plain" Qt classes which does not 
>>>>> allow
>>>>> Python re-implementations of C++ virtuals. This means that while 
>>>>> the Qt
>>>>> event loop is running (ie. in the call to exec()), *no* PyQt is 
>>>>> executed
>>>>> - yet the problem still exists. It's almost as if the very presence 
>>>>> of
>>>>> Python is having an effect.
>>>>> Any insight would be welcome...
>>>>> Phil
>>>> Short version:
>>>> Setting the environment variable QT_MAC_WANTS_LAYER to 1 may fix the
>>>> issue for macOS 10.15. The code at
>>>> https://code.woboq.org/qt5/qtbase/src/plugins/platforms/cocoa/qnsview_drawing.mm.html#108
>>>> indicates this won't work for 10.14.
>>> Setting the style with QApplication.setStyle() or the command line
>>> -style option also works. Both the fusion and windows styles function 
>>> as
>>> expected. Explicitly using the macintosh style results in the 
>>> rendering
>>> defect. I still don't know how the dark mode mac style is invoked, or
>>> why it works while the light mode style does not.
>> 
>> Setting QT_MAC_WANTS_LAYER or using fusion both work for me. Building 
>> against Qt v5.9 also works.
>> 
>> Whether this is a genuine Qt bug, or just an unresolved clash between 
>> Qt and Python settings on macOS is difficult to say.
>> 
>> Setting QT_MAC_WANTS_LAYER in the PyQt initialisation seems a 
>> reasonable workaround.
>> 
>> Does anybody know if the problems exists on macOS 10.14 and earlier?
>> 
>> Phil