Bug in Qt 5.12 drag n'drop ?

skylendar · 14 Dec 2018, 21:19

Ok, I'm using Qt 5.12.0 Linux x86_64 downloaded directly from qt.io.
Apparently, this bug (behavior ?) doesn't seem to be listed in the bugs db.
I patched both QWidget::dragEnterEvent() and QWidget::dropEnterEvent() for a specific widget. It has been working for at least 10 years, but with 5.12.0 dragEnterEvent() is executed, and not dropEnterEvent().

In my code, I used event->acceptProposedAction() instead of event->setAccepted(true), but it worked fine.

skylendar · wrote on 14 Dec 2018, 21:19

@skylendar

I also tried the dnd robot example which uses event->setAccepted(true) in its dragEnterEvent(). It works but when I do the same in my code, zip...

SGaist · 14 Dec 2018, 22:35

Can you spot any difference between the example and what you do in your application ?

skylendar · S SGaist 14 Dec 2018, 22:18

@SGaist

Yes, "robot" works but not my app, which is not that different, at least about dnd

SGaist · 14 Dec 2018, 22:39

"not that different" can be a big can of worm ;)

skylendar · 14 Dec 2018, 22:42

@SGaist

wait, i'm testing again..

skylendar · 14 Dec 2018, 22:44

@skylendar

Ah, "robot" is based on a QGraphicsObject, which receives QGraphicsSceneDragDropEvent , whereas my app is based on a mere QWidget, which receives a QDragEnterEvent

skylendar · wrote on 14 Dec 2018, 22:44

@skylendar

And remember, my code works fine with qt5.11.x, and not with qt5.12.0

Christian Ehrlicher · 15 Dec 2018, 16:06

Please provide a example - otherwise I don't see how we can spot the problem...

skylendar · wrote on 15 Dec 2018, 16:06

@Christian-Ehrlicher

Ok, in that case, get my open source app:
https://sourceforge.net/projects/skylendar/
and compile it with qt5.12.0
When compiled and running, drag the "Now" Dataset (on the left column) onto the window named "Standard wheel".

Then, the pointer becomes a barred red circle, instead of a black hand for dropping, i.e. dropping is impossible.

When compiled with 5.11 apparently nothing happens because the standard wheel already uses "Now", but it works...

Christian Ehrlicher · 15 Dec 2018, 16:30

I tried to run your app but I won't let something run as root on my system. Please provide a minimal, compilable example to reproduce the issue.

aha_1980 · 15 Dec 2018, 16:40

@Christian-Ehrlicher

I tried to run your app but I won't let something run as root on my system.

probably the elevated rights are part of the problem?

Christian Ehrlicher · wrote on 15 Dec 2018, 16:40

@aha_1980 said in Bug in Qt 5.12 drag n'drop ?:

probably the elevated rights are part of the problem?

Don't think so - it's using a database and the app which creates the schema etc. wants admin rights. After this it looks like the normal application can run without admin rights but did not came that far.

skylendar · wrote on 15 Dec 2018, 16:44

@aha_1980

No, only skydmin needs admin right in order to install the db. skylendar runs as a normal user.

skylendar · 15 Dec 2018, 16:54

@aha_1980

If you really are scared to run skydmin as root, I can tell you how to install the db as the postgres non-root user.

aha_1980 · 15 Dec 2018, 17:00

@skylendar Thanks, but I don't think I'll debug your program ;)

I have too much of my own problems

skylendar · wrote on 15 Dec 2018, 17:00

@aha_1980

I don't ask you to debug my app, just run it.

skylendar · 15 Dec 2018, 17:28

@aha_1980

In addition, I don't want anything. I just signal a possible bug. That's all.

aha_1980 · 15 Dec 2018, 17:50

@skylendar thats why we need a simple program, trimmed down to the actual problem.

Otherwise its hard to track down where the bug is. Until now it is not even proven that Qt is guilty.

skylendar · wrote on 15 Dec 2018, 17:50

@aha_1980

This is not a matter of guilt or not. We are not in an american thriller.
And besides, how do you explain that my app works fine with qt5.11 and below, but not with qt5.12 ?