• Li Jie (86/86) Apr 12 2007 I want to call XPCOM and write XPCOM component with D, but I have some p...
• Chris Nicholson-Sauls (7/111) Apr 12 2007 I would think a merge of options 3. and 4. would be good. Ie, add eithe...
• Li Jie (14/125) Apr 21 2007 My friend, h_rain has found a simple way, rename nsISupports to IUnknown...

Li Jie <cpunion gmail.com> writes:

I want to call XPCOM and write XPCOM component with D, but I have some problems.

This is COM object virtual table structure:






And this is XPCOM object virtual table:





extern(Windows) only compatible COM, because it added an offset, XPCOM do not
need this.
When call QueryInterface, it really call AddRef.
And I tried extern(C++) and extern(Pascal), no changes.

I think that there are 4 solutions:

1. Don't use interface, replace with struct, C style:




QueryInterface;  











Ugly! but it can works.


2. Modify XPCOM interface, remove QueryInterface method:















QueryInterface;  














It can works, replace nsISupports.QueryInterface with MyQueryInterface. But I
can't write XPCOM component with D, because no QueryInterface in interface.


3. Hack DMD:







Change to:






And add pointer to IUnknown:









I don't know whether it can work.

4. Hack DMD, add extern(XPCOM), I think it's very difficult to do.


Any ideas?

Chris Nicholson-Sauls <ibisbasenji gmail.com> writes:

Li Jie wrote:
 I want to call XPCOM and write XPCOM component with D, but I have some
problems.
 
 This is COM object virtual table structure:





 
 And this is XPCOM object virtual table:




 
 extern(Windows) only compatible COM, because it added an offset, XPCOM do not
need this.
 When call QueryInterface, it really call AddRef.
 And I tried extern(C++) and extern(Pascal), no changes.
 
 I think that there are 4 solutions:
 
 1. Don't use interface, replace with struct, C style:




QueryInterface;  










 
 Ugly! but it can works.
 
 
 2. Modify XPCOM interface, remove QueryInterface method:















QueryInterface;  













 
 It can works, replace nsISupports.QueryInterface with MyQueryInterface. But I
can't write XPCOM component with D, because no QueryInterface in interface.
 
 
 3. Hack DMD:






 
 Change to:
 




 
 And add pointer to IUnknown:








 
 I don't know whether it can work.
 
 4. Hack DMD, add extern(XPCOM), I think it's very difficult to do.
 
 
 Any ideas?

I would think a merge of options 3. and 4. would be good.  Ie, add either a
second 
interface (IXPUnknown perhaps) or an extern(XPCOM), and modify DMD's 
InterfaceDeclaration::vtblOffset to know about the special case.  It'd be
Walter's choice, 
and I'm not so sure XPCOM would be anywhere near the top of his priority list.

*ponder ponder*

-- Chris Nicholson-Sauls

Li Jie <cpunion gmail.com> writes:

Chris Nicholson-Sauls дµ½:

 
 Li Jie wrote:
 I want to call XPCOM and write XPCOM component with D, but I have some
problems.
 
 This is COM object virtual table structure:





 
 And this is XPCOM object virtual table:




 
 extern(Windows) only compatible COM, because it added an offset, XPCOM do not
need this.
 When call QueryInterface, it really call AddRef.
 And I tried extern(C++) and extern(Pascal), no changes.
 
 I think that there are 4 solutions:
 
 1. Don't use interface, replace with struct, C style:




QueryInterface;  










 
 Ugly! but it can works.
 
 
 2. Modify XPCOM interface, remove QueryInterface method:















QueryInterface;  













 
 It can works, replace nsISupports.QueryInterface with MyQueryInterface. But I
can't write XPCOM component with D, because no QueryInterface in interface.
 
 
 3. Hack DMD:






 
 Change to:
 




 
 And add pointer to IUnknown:








 
 I don't know whether it can work.
 
 4. Hack DMD, add extern(XPCOM), I think it's very difficult to do.
 
 
 Any ideas?

 
 I would think a merge of options 3. and 4. would be good.  Ie, add either a
second 
 interface (IXPUnknown perhaps) or an extern(XPCOM), and modify DMD's 
 InterfaceDeclaration::vtblOffset to know about the special case.  It'd be
Walter's choice, 
 and I'm not so sure XPCOM would be anywhere near the top of his priority list.

My friend, h_rain has found a simple way, rename nsISupports to IUnknown, like
this:

---------------------------------------
extern(Windows)
interface IUnknown {
  // some methods
}

alias IUnknown nsISupports;

extern(Windows)
interface nsIFile : nsISupports {
  // some methods
}
---------------------------------------

It works fine, and it is beautiful.