[Lazarus] Custom Form design time rendering problem

[Horacio Jamilis]

Hi,

I am migrating a Delphi system to Lazarus.

Each object of the system is represented in a TFrame.

The declaration of TSystemObject (base object/frame) is:

{$ifdef BASE_SYSTEMOBJECT_ON_OBJECT}
   TSystemObject = class(TObject)
{$else}
   TSystemObject = class(TFrame)
{$endif}
   public
     constructor Create(AOwner : {$ifdef 
BASE_SYSTEMOBJECT_ON_OBJECT}TObject{$else}TComponent{$endif}); {$ifdef 
BASE_SYSTEMOBJECT_ON_OBJECT}virtual;{$endif}
     constructor CreateObject(aOwner : {$ifdef 
BASE_SYSTEMOBJECT_ON_OBJECT}TObject{$else}TComponent{$endif}{; const 
aSystemData : TSystemData = nil}); virtual;
   end;

The conditional BASE_SYSTEMOBJECT_ON_OBJECT make it act as a frame at 
design time, and as a TObject at runtime. Then at runtime I create the 
designed frame by code when required.
In Delphi (any version) it works. In Lazarus, I can not see the 
components at design time (I don't know at runtime because I did not 
finished the porting and does not compile yet).

I registered it with 
FormEditingHook.RegisterDesignerBaseClass(TSystemObject);
The registration went well! I installed the package ok. The properties 
of the TSystemObject are on the object inspector as expected.

When I open a unit with a SystemObject created in Delphi, it opens, but 
the components inside it (in the frame) are not rendered at design time.
I can select them with a mouse clic, and the properties of them are ok 
in the object inspector, but the component is not visible on the form.
Even if I add a TButton, it is not visible.

What could be wrong?

Using .dfm in place of .lfm could be a problem?

Then I changed the base class to TForm (in place of TFrame), and 
registered it as in the custom form example with 
RegisterCustomForm(TSystemObject,'SystemObject');
This worked as it appears in the new menu dialog. How to do this with 
TFrame?

Thank you!

Horacio Jamilis
Buenos Aires, Argentina