Getting ready to Qt 6 (3/n). Do not use QKeyEvent copy constructor

[hebasto]

This PR is preparation for Qt 6, and it fixes an experimental build with Qt 6.2.4 as copying of QEvent has been disabled in Qt 6.0.0.

[shaavan]

ACK d543515

• I was able to verify that with Qt 6, the copying of QEvent has been disabled. See for reference {second and third paragraph}.
• Therefore, instead of copying the key event, this PR uses its data to create a new event.

nit:

As a minor nit, I would suggest creating a variable type instead of calling keyevt→type() multiple times.

QEvent::Type type = keyevt->type()

[hebasto]

Updated d543515 -> 8691a44 (pr580.01 -> pr580.02, diff):

• addressed @shaavan's comment

[shaavan]

reACK 8691a44

Changes since my last review:

• Declared a type variable beforehand and used it instead of keyevt→type().

[luke-jr]

Why are we creating a new event instead of forwarding the original one on? Seems like this PR would simply be bypassing the behaviour Qt is trying to prevent...

[hebasto]

Why are we creating a new event instead of forwarding the original one on? Seems like this PR would simply be bypassing the behaviour Qt is trying to prevent...

QCoreApplication::postEvent:

The event must be allocated on the heap since the post event queue will take ownership of the event and delete it once it has been posted. It is not safe to access the event after it has been posted.

"forwarding the original one on" ends with double deletion of an QKeyEvent instance.

[luke-jr]

Hmm, how about using https://doc.qt.io/qt-5/qcoreapplication.html#sendEvent ?

[hebasto]

Updated 8691a44 -> 3ec6504 (pr580.02 -> pr580.03, diff):

• addressed @luke-jr's comment

[w0xlt]

tACK 3ec6504 on Ubuntu 21.10, Qt 5.15.2

[shaavan]

reACK 3ec6504

Changes since my last review:

• Instead of creating a new event for each call of postEvent, send Event is used with keyevt event.

Since sendEvent does not delete the event argument after the completion of its execution, the same keyevt could be used multiple times instead of creating a separate event for each instance of using postEvent. Therefore I agree with this change.

References:

• postEvent: https://doc.qt.io/qt-6/qcoreapplication.html#postEvent
• sendEvent: https://doc.qt.io/qt-6/qcoreapplication.html#sendEvent
• Comparison between the two: https://doc.qt.io/archives/qq/qq11-events.html (under section Synthetic Events)