[Lazarus] TControl.Click?
Mattias Gaertner
nc-gaertnma at netcologne.de
Sat Oct 1 08:53:31 CEST 2011
On Sat, 01 Oct 2011 03:04:56 +0200
Hans-Peter Diettrich <DrDiettrich1 at aol.com> wrote:
> I don't understand the logic behind TControl.Click:
>
> procedure TControl.Click;
> begin
> //DebugLn(['TControl.Click ',DbgSName(Self)]);
> if (not (csDesigning in ComponentState)) and (ActionLink <> nil) and
> ((Action=nil) or (@FOnClick <> @Action.OnExecute) or
> Assigned(FOnClick)) then
> ActionLink.Execute(Self)
> else
> if Assigned(FOnClick) then
> FOnClick(Self);
> end;
>
> This IMO will invoke ActionLink.Execute if (a different) FOnClick is
> assigned - so far okay. But FOnClick will *not* be invoked then (even if
> different), and it will be invoked *always* in design state.
>
> Is it really okay to invoke an user-supplied OnClick handler in design
> state?
No.
User supplied OnClick handlers are fake methods and that's why
"Assigned" is used instead of "FOnClick<>nil". Thus user handlers are
*not* invoked.
Only real methods are invoked. That means custom component handlers are
invoked.
> What about something like this:
>
> if (csDesigning in ComponentState) then
> exit; //nothing called in design state
> if (ActionLink <> nil)
> and ((Action=nil) or (@FOnClick <> @Action.OnExecute) then
> ActionLink.Execute(Self); //only if different from FOnClick
> if Assigned(FOnClick) then //eventually also: if not handled?
> FOnClick(Self); //always if assigned
> end;
>
> I also wonder what's the difference or relationship between Action and
> ActionLink - can somebody explain? Does ActionLink (when assigned) take
> precedence over Action?
See TControl.GetAction.
Then lol.
Mattias
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