OpenEuphoria

Re: Inheriting win32 Handles

• Posted by Derek Parnell <ddparnell at bigpond.com> Feb 07, 2003
• 406 views

On Thu, 6 Feb 2003 23:27:53 -0000, <jordah at btopenworld.com> wrote:

>
> Hi all,
> I was just writing my own EUWIN. when i came across something funny. I
> wanted to Inherit win32 Handles to respond to basic events just as if 
> they
> were created by EUWIN. After doing that i just checked win32lib's
> subclasscontrol().
>
> I noticed in win32lib, you subclass a control by also assigning it a "new
> parent". How about the original parent of the control? What if the 
> original
> parent of the control is also a handle? This would mean getParent() would
> fail...and this would lead to other successive errors.
>
> Correct me if i'm wrong?

Okay, I'll give it a try.

Firstly, the routine subClassControl() is documented that it only applies 
to controls that Windows has created and win32lib does not know about. Such 
as the edit box area for a combo box. The routine is used to 'simulate' 
creating the edit box as if win32lib had created it. It does NOT change 
it's parentage in the strict Windows sense. The purpose of this routine is 
so that we can use the normal win32lib events and other routines on a 
control that Windows created. To do this, it just creates the structures 
inside win32lib to support it, It does not create a Windows control as that 
already exists.

Secondly, there is an undocumented use for this routine. This other use is 
just so that I don't have duplicated code hanging around. Internally I call 
the routine when win32lib has created a control in order to create the 
supporting internal structures.

Now, if you supply the 'parent' value as a hWnd type, you are doing the 
wrong thing. The documenation says that the parent value is an Id - that 
is: a value returned to you from a previous call to create().

-- 

cheers,
Derek Parnell