Qt does not position forms

[systemgvp]

Situation:
 - kubuntu 26.04
 - lazarus 4.6
 - wayland

Using gtk3, qt5 or qt6, if I set a form position, it isn't executed. Using gtk2, it is. Example:

1. I create a new empty application
2. I set position=poDesigned
3. I add a button and associate Form1.Left:=0;
4. I compile

If I click on button1, the form doesn't move, but stays in the center of the screen.
What's missing? Why does it only work with GTK2?
On Kubuntu 25.10, Lazarus doesn't cause any problems, even on Windows.

[Alexx2000]

Wayland does not support changing window position. GTK2 executes using Xwayland that's why it works.

[Thaddy]

Basically it should NOT work, because Xwayland <> Wayland and by now everybody knows that the cause is not Lazarus or has been sleeping under a rock.
Everybody else also knows that Wayland has by now an extended API that allows for Windowing management a bit better, but no one has implemented it yet (that includes Lazarus, but also the rest of the world except for tests).
It is rather pointless to discuss this any further. Just automatically refer to the Wayland developers.

Btw: Qt6 is a lot better than GTK2.

And you @Alexx2000 already know all that. Don't even mention GTK2 is a Qt thread.

[systemgvp]

Yes, Qt6 is a lot better than GTK2, but unfortunately, I need to set the shape's position in my application. Are you aware of any Wayland scams?

[valdir.marcos]

Yes, Qt6 is a lot better than GTK2, but unfortunately, I need to set the shape's position in my application. Are you aware of any Wayland scams?

There is no immediate solution for Wayland.

The alternative, if possible in your case, would be to switch to XLibre:

Ubuntu Repository for XLibre
https://github.com/xlibre-debian/ubuntu

About XLibre:
https://github.com/X11Libre/xserver

[zeljko]

Yes, Qt6 is a lot better than GTK2, but unfortunately, I need to set the shape's position in my application. Are you aware of any Wayland scams?

You can use Qt6 on same system where gtk2 is used, QT_QPA_PLATFORM=xcb ./yourapp should work.

[systemgvp]

where should I put this string?

[zeljko]

Put it as env variable just like I shown you for test. If that works you can start your app via script. Adding it globally into your $HOME/.bashrc isn't clever idea if you're on KDE Plasma wayland because then everything will be x11/xcb...

[systemgvp]

Sorry, but I don't understand where to insert the variable. Where is this test?

[zeljko]

In linux terminal: QT_QPA_PLATFORM=xcb ./yourapp , or if you run app via lazrus debugger, Run -> Run parameters -> click second tab "Environment", click Add button below, write env variable name QT_QPA_PLATFORM, for value set xcb, now run your qt6 app.

[systemgvp]

Thanks, both solutions work with QT6. I hope they are only a temporary solution.

[dbannon]

You can also add a command line parameter if thats more intuitive -

Code: Pascal  [Select][+][-]

1. $> my-app -platform xcb

Note its only one dash (should be two) and no '=' but the parameter is filtered out by Qt before it gets to your app, so does not cause problems with your command line parsing.

Davo

[Fred vS]

Gemini propose this:

Code: Pascal  [Select][+][-]

1. program YourAppName;
2.  
3. {$mode objfpc}{$H+}
4.  
5. uses
6.   {$IFDEF LINUX}
7.   Unix, // Required for fpGetEnv and fpSetEnv
8.   {$ENDIF}
9.   Interfaces, // Initializes the Lazarus widgetset
10.   Forms,
11.   Unit1;
12.  
13. {$IFDEF LINUX}
14. procedure CheckAndForceXCB;
15. var
16.   SessionType: String;
17. begin
18.   // Retrieve the current desktop session type
19.   SessionType := LowerCase(fpGetEnv('XDG_SESSION_TYPE'));
20.  
21.   // If running on Wayland, force Qt to fallback to XCB (via XWayland)
22.   if SessionType = 'wayland' then
23.   begin
24.     fpSetEnv('QT_QPA_PLATFORM', 'xcb', 1);
25.   end;
26. end;
27. {$ENDIF}
28.  
29. begin
30.   {$IFDEF LINUX}
31.   // This must execute before the Interfaces unit initializes Qt
32.   CheckAndForceXCB;
33.   {$ENDIF}
34.  
35.   Application.Initialize;
36.   Application.CreateForm(TForm1, Form1);
37.   Application.Run;
38. end.
39.  

[systemgvp]

The problem is that I would like this solution to be already included in the application, and not have to start the app manually every time

In linux terminal: QT_QPA_PLATFORM=xcb ./yourapp , or if you run app via lazrus debugger, Run -> Run parameters -> click second tab "Environment", click Add button below, write env variable name QT_QPA_PLATFORM, for value set xcb, now run your qt6 app.

[systemgvp]

As always when using AI things don't work, in fact lazarus doesn't recognize the fpGetEnv() and fpSetEnv() functions

Gemini propose this:

Code: Pascal  [Select][+][-]

1. program YourAppName;
2.  
3. {$mode objfpc}{$H+}
4.  
5. uses
6.   {$IFDEF LINUX}
7.   Unix, // Required for fpGetEnv and fpSetEnv
8.   {$ENDIF}
9.   Interfaces, // Initializes the Lazarus widgetset
10.   Forms,
11.   Unit1;
12.  
13. {$IFDEF LINUX}
14. procedure CheckAndForceXCB;
15. var
16.   SessionType: String;
17. begin
18.   // Retrieve the current desktop session type
19.   SessionType := LowerCase(fpGetEnv('XDG_SESSION_TYPE'));
20.  
21.   // If running on Wayland, force Qt to fallback to XCB (via XWayland)
22.   if SessionType = 'wayland' then
23.   begin
24.     fpSetEnv('QT_QPA_PLATFORM', 'xcb', 1);
25.   end;
26. end;
27. {$ENDIF}
28.  
29. begin
30.   {$IFDEF LINUX}
31.   // This must execute before the Interfaces unit initializes Qt
32.   CheckAndForceXCB;
33.   {$ENDIF}
34.  
35.   Application.Initialize;
36.   Application.CreateForm(TForm1, Form1);
37.   Application.Run;
38. end.
39.