Regarding Linux GTK3 T[Xxx]Dialog component issues

[energy]

Hello,

I am the lead developer of the Energy framework, which is a full set of API libraries for Golang based on the Laz LCL component library's encapsulation.

At present, I have encountered some issues while encapsulating the components.

Under Linux GTK3, because I need the functionality of Gtk3, which I know is still in the beta-testing stage and not yet perfected.

Currently under Gtk3, when encapsulating Dialog-related components, I found that they do not work normally. These include components (TSelectDirectoryDialog, TOpenDialog, TSaveDialog), and there may be others.
The problem occurs when executing the Execute function, and during the Debug tracking, an error appeared at "TGtk3WSOpenDialog.CreateHandle(const ACommonDialog: TCommonDialog): THandle;".
It occurred during the call to CreateOpenDialogHistory and CreateOpenDialogFilter.
Solution: I found that these functions used "virtual" modifier. After removing the "virtual" modifier, it can run normally.
I am not clear why the removal of the "virtual" modifier allows it to run normally. I am not sufficiently knowledgeable in this area.


Here is the code snippet：

  TGtk3WSOpenDialog = class(TWSOpenDialog)
  protected
    class function CreateOpenDialogFilter(OpenDialog: TOpenDialog; Chooser: PGtkFileChooser): string;// virtual;
    class procedure CreateOpenDialogHistory(OpenDialog: TOpenDialog; SelWidget: PGtkWidget);// virtual;
    class procedure CreatePreviewDialogControl(PreviewDialog: TPreviewFileDialog; Chooser: PGtkFileChooser);// virtual;
  published
    class function CreateHandle(const ACommonDialog: TCommonDialog): THandle; override;
  end;

Lazarus: 3.2
System: ubuntu 22
Energy Open source address: https://github.com/energye/energy

[jamie]

There must be a disruption in the force!

I didn't know a CLASS function could be virtual? also, I am trying to imagine how that would work?

I just did a compilation of a Class function returning a Boolean and it compiles and runs.

Strange things.

[energy]

code file: lazarus/3.2.0/lcl/interfaces/gtk3/gtk3wsdialogs.pp

method: TGtk3WSOpenDialog.CreateHandle

Here is the place where the function call occurs; errors are reported at both spots.

  // History List - a frame with an option menu
  CreateOpenDialogHistory(OpenDialog, Dlg.Widget);

  // Filter
  // InternalCreateOpenDialogFilter
  CreateOpenDialogFilter(OpenDialog, Chooser);

The error occurs during runtime when invoking the function. Removing the "virtual" keyword allows the function to run normally.

[jamie]

This is strange code however, it seems that class needs to be created first, even though all you see is class methods there.

The base Class however, I believe requires construction.

 The Dialog Handle in the windows widget is a class that needs to be constructed so it's my guess that maybe you are dealing with that?

[energy]

I directly dragged the TSelectDirectoryDialog component through the Laz IDE, and then triggered its "Execute" method using a TButton's Click event.

procedure TForm1.SelectDirDialogBtnClick(Sender: TObject);
begin
  SelectDirectoryDialog1.InitialDir := '/';
  SelectDirectoryDialog1.Execute;
end;

This is a very simple feature; just drag TSelectDirectoryDialog and a TButton onto the form, and trigger it inside the TButton. No additional operations are needed.

[AlexTP]

Create the smallest example, which shows the problem (error at runtime). It must be runtime error, not compile error. So you can post the bugreport with example.

[energy]

The attachment is an example program for Ubuntu 22, Lazarus 3.2.
Note: "LCLWidgetType:=gtk3"

[energy]

Attachments are GIF records of operations

[energy]

Dialog_success.gif is the removed 'virtual'

[AlexTP]

You have Access Violation so I guess it is a plain bug of Lazarus. I think you can post the bug report to GitLab.

But, delete 'lib' dir from your zip.

[jamie]

if you don't use forms, don't you need to use the "Interfaces" unit somewhere in your code to get the full widget initiated ?

[energy]

OK
delete lib dir
Send report to GitLab