Re: [paragui-users] the dll low down

[Alexander Pipelka]

Hmm,...

There's one thing that came to my mind after your last email:
Are you linking your dll's statically to ParaGUI (I think i read this in
your CWproject readme) ?

It won't work this way.

Why ?

Because ParaGUI hold a whole bunch of static variables (the globall app
object, widgetlists, messagemaps,...).
If you link it statically every dll will be a seperate ParaGUI instance.

Solution ?
Create a ParaGUI dll and link it with your main app and your "plugin"
dlls.

Alex

Am Die, 2002-06-04 um 17.29 schrieb Keith Swyer:
> ok, i'll geive you some nice details.....
> 
> - i am using a base class that all the dlls are based from
> 
> class Area{
> public:
>     virtual void FillArea(void *data, void *data2) = 0;
> private:
>     friend class dll_object_ref<Area>;
>     virtual void destroy()=0;
> };
> 
> - in the dlls i create i use the Area base class, then call a macro
> FACTORY_ENTRY(newclass, name)
> which then calls this....  allowing us to have a clean way to access the
> names without the c++ mangled crap.
> (externc is a macro for extern "c" and dllfunc is just the export )
> #define FACTORYFUNC( base , the_class , prefix , classid ) \
>   EXTERNC DLLFUNC base* DLLCALL prefix##classid( void )    \
>     { return new the_class; }
> 
> - these are the DLL support classes: dll_sentinel, dll_object_ref, and
> dll_object_ptr.
> Class dll_sentinel is responsible for ensuring that the DLL is resident
> during the sentinel's lifetime. It keeps track of both the DLL name and the
> handle to that DLL. The first time a dll_sentinel is created, it asks the OS
> to load the DLL, and the OS sets the DLL's reference count to one. Every
> time another dll_sentinel loads the same DLL, the OS increments that DLL's
> reference count. When each dll_sentinel is destroyed, it asks the OS to
> close the DLL. The OS actually just decrements the DLL's reference count,
> and unloads the DLL only when that count reaches zero.
> dll_object_ref contains a dll_sentinel, a pointer to an object residing in
> the DLL, and a reference count. When a dll_object_ref is constructed, it
> finds the appropriate function in the DLL and uses it to initialize its
> pointer. When the dll_object_ref is destroyed, it deletes the object pointed
> to.
> 
> dll_object_ptr is similar to std::auto_ptr, except that its ownership
> semantics are slightly different. Copying one dll_object_ptr to another does
> not cause one of them to become invalidated or to lose ownership of the
> underlying object. Because dll_object_ptr takes advantage of
> dll_object_ref's reference counting scheme, the underlying object gets
> destroyed only when all of its dll_object_ptrs are destroyed.
> 
> Now that i hopefully have you all confused  :)  i don't have a way that each
> dll instanciates themselves automatically yet, but right now my factory
> template allows you to instantiate by referring to the name of the
> class.....anyway, this all works fine and i can call _object->FillArea
> fine, but inside of that function in the dll i cannot use any of the paragui
> functions.
> 
> 
> 
> well, i hope this isn't too much to wrap your heads around as i know i'm
> getting a litte off paragui specific (but i am planing to add this somehow
> to pg) any help would be great. I know this isn't probably the best way to
> do what i'm doing, but i've had to figure this all out by looking around the
> net, and i'm only new to using and making dlls...   :)
> 
> 
> 
> --Keith
> 
> 
> 
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