Hi,

What is the correct way to clone programmatically a component, ie assign all its properties to another component of the same class (like the IDE designer's copy/paste)?

The code below used to work in Delphi but does not with Lazarus (result
is nil).
     RegisterClass(TMyComponent);
     Clipboard.SetComponent(MyComponent);
     Result:= TMyComponent(Clipboard.GetComponent(Self, Self));

Stephano

It should work in Lazarus too.

Mattias

It does not. It seems due to the fact that TClipboard.GetComponent uses pcfComponent while TClipboard.SetComponent uses pcfCustomData instead. Substituting pcfCustomData by pcfComponent did the job, but then the copied (original) component seems to lose its events. I will test further and report.

Stephano

The copied (original) component's events are fine. However, it is the clone's events which are not as desired. Its methods code+data are equal to the original component's methods code+data whereas the data part should point to the clone itself for proper operation of the clone. Any ideas on how this should be handled?

Stephano

I have gathered the following presumed bugs:

1- TClipboard.GetComponent uses pcfComponent while TClipboard.SetComponent uses pcfCustomData instead.

2- Clipboard.SetComponent/GetComponent do not save/restore events. Events are nil. This is the clipboard text of a button with an assigned OnClick event (note the missing OnClick):
object Button1: TButton
Left = 24
Height = 25
Top = 16
Width = 139
Caption = 'Button1'
Font.Height = -20
Font.Name = 'Sans'
ParentFont = False
TabOrder = 0
end

Stephano

I don't think that the clipboard should contain pointers, which become invalid as soon as the referenced form is closed.

The data pointer should refer to the *form* containing the cloned component. When that form doesn't have the named method, the handler reference may be cleared.

DoDi

The lfm stream does not contain pointers.
The reader has just the wrong root component.

The data pointer should refer to the *form* containing the cloned component. When that form doesn't have the named method, the handler reference may be cleared.

Mattias

Please report this bug.

Are you sure that Delphi SetComponent writes events?

Mattias

Done: http://bugs.freepascal.org/view.php?id=23060

No. But I was assuming that events would be written as is the case with lfm's:
object Button1: TButton
Left = 68
Height = 25
Top = 29
Width = 75
Caption = 'Button1'
OnClick = Button1Click <---------
TabOrder = 0

   end

Stephano

patspiper hat am 5. Oktober 2012 um 09:56 geschrieben:

The Button1Click is a method of the form or a nested frame, not the Button1. The streaming need some extra params to handle events.

Mattias