[fpc-devel] Streaming readonly properties

[Michael Van Canneyt]

On Wed, 13 Dec 2006, Vincent Snijders wrote:

> Michael Van Canneyt schreef:
> > 
> > On Wed, 13 Dec 2006, Vincent Snijders wrote:
> > 
> > > Michael Van Canneyt schreef:
> > > > On Wed, 13 Dec 2006, Vincent Snijders wrote:
> > > >
> > > > > Michael Van Canneyt schreef:
> > > > > > On Tue, 12 Dec 2006, vsnijders at quicknet.nl wrote:
> > > > > >
> > > > > > > As said in an earlier mail I have problems streaming the property
> > > > > > > EditLabel: TBoundLabel read FEditLabel;
> > > > > > > of a TLabeledEdit with fpc 2.1.1.
> > > > > > >
> > > > > > > Some discussion on #fpc led to the conclusion that streaming a
> > > > > > > readonly
> > > > > > > persistant should be allowed, because you write to the properties
> > > > > > > of
> > > > > > > the
> > > > > > > readonly persistant property.
> > > > > > >
> > > > > > > Attached is a proposal to fix it.
> > > > > > Delphi does not stream readonly properties. So we won't either.
> > > > > >
> > > > > > The proper solution for this is support for csSubComponent in
> > > > > > TComponent.
> > > > > Can you elaborate a bit, what you mean by that? What should be changed
> > > > > and
> > > > > where?
> > > > Delphi has a ComponentState csSubComponent. This flag should be set
> > > > if you publish a property of type TComponent, and the TComponent
> > > > instance
> > > > is 'owned' by the object that publishes it, i.e. it's NOT a reference to
> > > > an
> > > > other existing TComponent.
> > > >
> > > > The owned TComponent has 'csSubComponent' in it's componentstyle. This
> > > > tells
> > > > delphi to stream the component's properties as part of it's owning
> > > > component, and not just a reference to it.
> > > >
> > > > The IDE will need support for this, as well TComponent and the streaming
> > > > system. (The latter part is probably the easy part ;) )
> > > So far so good.
> > >
> > > The IDE supports this (no drop downbox in the IO, but you can expand to
> > > set
> > > the owned component's properties). The owned component has the
> > > csSubComponent
> > > in its component style:
> > >
> > >   Include(FEditLabel.ComponentStyle, csSubComponent);
> > >   Include(FEditLabel.ControlStyle, csNoDesignSelectable);
> > >
> > > So where should the streaming occur?
> > 
> > When EditLabel is encountered ?
> 
> I am not sure I understand your question.
> 
> EditLabel is a published property of TLabeledEdit.

I know that, but it was not a question, so read as

"When EditLabel is encountered."

:-)

When you do the streaming, I assume you'll have to set some
extra flag in the stream, probably you'll need to check Delphi 
streaming code for the value of this flag... (but I'm not sure)

Michael.