Re: [gtkmm] Passing a pointer to a class using D&D

[Vladislav Grinchenko <3rdshift comcast net>]

Ryan,

why bother - if you dnd in the same application, you can keep
all info you want in a temp object visible to both source and 
target. I tried it all a couple of weeks ago and discovered that
passing casted pointers to anything is clearly dangerous.
String are fine but that's about it.

Here's what I ended up with -
source -
http://cvs.sourceforge.net/viewcvs.py/granule/granule/src/DeckList.cpp?rev=1.10&view=auto
(on_drag_begin(), on_drag_data_get())

target -
http://cvs.sourceforge.net/viewcvs.py/granule/granule/src/CardBox.cpp?rev=1.35&view=auto
(on_deck_dropped_cb())

hope this helps,
-Vlad


On Thu, 2004-08-05 at 09:12, Miller, Ryan D wrote:
> Greetings everyone,
> 
> Another question for the great readers of gtkmm list.  I need to access
> several fields of information from a class after a user performs a drag
> from that class onto another one.  (Both classes are derived from
> EventBoxes).  I figured out how to pass a single value, such as a
> string, based on the examples by casting the string into a guchar* and
> then using get_data_as_string on the receiving end.  In order to pass
> more than one thing, I was hoping to pass the address of the passing and
> then create a pointer to the passing class on the receiving end and use
> that to access what I need.  Is this a feasible way to do this?  In a
> more concise manner: I would like to pass a pointer to "this" using D&D.
> The code I have right now is below, but I end up with different values
> for the addresses on both ends.  Does anyone know how to do this?
> 
> In drag_data_get(..) in my passing class:
> 
>   Selection_data.set( selection_data.get_target(), 8, (const guint8
> *)this, sizeof(this));
> 
> In drag_data_received(..) in my receiving class (templateBoxTarget):
> 
>   templateBoxTarget *t = (templateBoxTarget *)
> selection_data.get_data();
> 
> And I have also tried something like this as a shot in the dark, but got
> the same results:
>   void *pVoid = (void *)selection_data.get_data();
>   templateBoxTarget *t = static_cast<templateBoxTarget *> (pVoid);
> 
> Thanks!,
> Ryan
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-- 
_____________________________________________________________
Vladislav Grinchenko       http://home.comcast.net/~3rdshift/
                                 e-mail: 3rdshift comcast net
                                                   
      Focus on quality, and productivity will follow.
_____________________________________________________________