[Lazarus] TTabControl (d)evolution

[Hans-Peter Diettrich]

Felipe Monteiro de Carvalho schrieb:
> On Tue, Aug 2, 2011 at 11:29 PM, Hans-Peter Diettrich
> <DrDiettrich1 at aol.com> wrote:
>> I just tested a raw TCustomTabControl, and it worked immediately as a
>> TTabControl with the Win32 widgetset. After moving ChildClassAllowed into
>> TPageControl, it allows to add components of any type to its client area. If
>> you can verify this for the other widgetsets[1], the whole implementation of
>> TTabControl reduces to the handling (almost publishing) of the properties.
> 
> I am amazed that this worked in Carbon and in Qt, although I still
> have to test the much less reliable Gtk.

Fine :-)

I was very astonished myself, when I saw it working out-of-the-box. IMO 
  it should be made work with the remaining widgetsets, when there exist 
problems at all.


> But even if this works, TNewTabControl still lacks a designer, and I
> am not sure how one could design it. The pages will occupy all the
> client area, so it won't be possible to drop controls. Maybe one would
> need to create a new Sheet class for it and set it as invisible in the
> designer?

I see no need for an extra designer. The tabs should be handled either 
as implicit part of the component, like e.g. the borders of TGroupBox, 
or as a child component with Align accoding to the TabPosition.

Dropping controls should work by adding csAcceptControls, which is 
explicitly removed in the constructor (see according comment). This is 
another part that should be moved out of the base class, into TPageControl.


> This change seams correct in any case so I commited in rev 31849 the
> change to ChildClassAllowed and I ifdefed TNewTabControl with {$ifdef
> LCL_NEW_TABCONTROL} and added a registration for it so that you can
> set this define and test designing.

Okay, I'll restart immmmmediately :-)

The lessons from the preceding tries should help to make the move less 
painful...


>> More properties are missing, at least from the Win32 widgetset. The problem
>> is that in the current implementation all properties are passed to the
>> widgetsets in TCustomPage parameters, so that this class must be extended
>> with all currently unhandled properties, or dedicated methods have to be
>> added to TWSCustomTabControl. This can be done later, once we know how to
>> make TTabControl work at all, with all widgetsets.
> 
> It should not be a problem for TTabControl to have sheets if they are
> invisible in the designer and if you can drop components directly
> inside the main component. The existence of sheets seams to be
> indispensable for gtk for example, but they can be hidden enough so
> that they don't interfere with the expected usage of the control.

It may help to add the required page widgets in the gtk widgetsets only, 
and if they cannot be made invisible by omitting Show(), they possibly 
could have an zero extent, or can be moved outside the component bounds.

DoDi