[solved] Qt6 and the Save Dialog

[dbannon]

I am having a problem with my app with Qt6. When I 'execute' a Save Dialog, as per attached sample project, there is a delay, about 20 seconds, before I see the actual dialog. In my real app, the dialog then refuses to close but in the sample it works fine after the 20 seconds.

That 20 seconds appears to be similar to the DBUS time out ???

Anyway, very simple demo attached, single form, button that opens a Save Dialog. It has a gtk2 and Qt6 mode. I built this on a Debian Testing VM, maybe someone else can try out the project on a different platform please ?

zeljko, if someone else confirms it, do you want me to log it with GitLab Issues ?

Davo

[zeljko]

I've spotted Open dialog problems with Qt6 - very slow etc, there's no reason that it's slow because of LCL site, there must but something else related to Qt library.

[Jorg3000]

Hi!
I read about the same problem in Windows (not Qt), which was described in the German forum.
Is it a coincidence that the problem occurs on different operating systems or is the cause in Laz after all?

[zeljko]

Haven't tested windows yet

[zeljko]

Just tested Qt6 dialogs under mac - it works without problems or lags.

[zeljko]

https://bugreports.qt.io/browse/QTBUG-106870?jql=project%20%3D%20QTBUG%20AND%20text%20~%20QFileDialog%20ORDER%20BY%20created%20DESC

[zeljko]

One more - same issue on x11, so it's Qt 6.2.XX bug.
https://bugreports.qt.io/browse/QTBUG-97108?jql=project%20%3D%20QTBUG%20AND%20text%20~%20QFileDialog%20ORDER%20BY%20created%20DESC

[zeljko]

Just tested on Manjaro Linux (fully updated, contains Qt6-6.4 libs) and it works ok. So definitelly Qt6 6.2 and probably 6.3 bug.

[theo]

Yes, no such problem here.
Lazarus 2.3.0 (rev main-2_3-2348-gecf49109b1) FPC 3.2.2 x86_64-linux-qt6
OpenSUSE Tumbleweed. Qt 6.4.0

[bobby100]

I have extremely slow Open and Save dialogs on Windows (LCL/native, no QT) if the apps are started from Lazarus in Debug mode. Release versions are OK.

[zeljko]

That is not related to this issue which is Qt lib only.

[dbannon]

OK, starting to sound understandable.

I see this problem on -

* U22.04 that is using Qt 6.2.4 and will be like that for live of U22.04
* Debian Testing, Qt 6.3.2 but will almost certainly have a new version before it become Bookworm

I guess we'll just have to say on the Wiki that Qt6 itself is not really a "thing" until you get to 6.4.0 - sad but true.

The perils of a long release cycle ....

Davo

[zeljko]

OK, starting to sound understandable.

I see this problem on -

* U22.04 that is using Qt 6.2.4 and will be like that for live of U22.04
* Debian Testing, Qt 6.3.2 but will almost certainly have a new version before it become Bookworm

I guess we'll just have to say on the Wiki that Qt6 itself is not really a "thing" until you get to 6.4.0 - sad but true.

The perils of a long release cycle ....

Davo

*U22.04 that is using Qt 6.2.4 and will be like that for live of U22.04*

No, 6.2.xx is LTS release and there will be 6.2.5, 6.2.6....so U22.04 will get update. I just hope that they'll fix this ugly dialogs slowness in next version of 6.2 LTS.

[dbannon]

 > U22.04 that is using Qt 6.2.4 and will be like that for live of U22.04*

No, 6.2.xx is LTS release and there will be 6.2.5, 6.2.6....so U22.04 will get update. I just hope that they'll fix this ugly dialogs slowness in next version of 6.2 LTS.

So, that will involve Qt fixing it in 6.2.* AND Ubuntu pushing that fix to U22.04. Trouble with that is that Debian have no interest in 6.2 series, they don't have Qt6 in Bullseye and have a 6.4 in Experimental. It won't be long before that 6.4 is in Testing and that, or something even newer, will be in Bookworm. So, if Ubuntu want a fixed up 6.2 for U20.04, they will have to do it themselves.   

EDIT: "pushing that fix to U22.04" not U20.04 as I initially said. Never going to make it to U20.04 !
I have to add that it seems a pretty obvious bug to get past Qt themselves, then Debian and then Ubuntu.

Davo

[zeljko]

Well, then it's not point of LTS distro with LTS packages IMO. If they distribute 6.2.xx LTS then they should update micro (patch) version changes because they contain only bugfixes, otherwise what's diff between LTS distro and Fedora with 6 months cycle ?