🚀 go-pugleaf

A couple of days ago I posted an item asking for help on creating 
instance specific data for a window.  I am summarizing the responses I
have received so far:

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neil@bedford.pro suggested the following: 

>I think that there are two approaches.
>
>The first is to disable the menu item which allows the user to pull up another
>box when one is already up (& enable it when the box goes away).
>
>The other is that the WM_INITDIALOG message can give you an instance pointer
>which you can use to separate the incarnations.

Later he elaborated on another method:

>Set/Get WindowLong is perfect for storing a pointer to instance data.
>I don't think it will work for dialog boxes, however.  I think db are a
>different beast.

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sybase!juan@Sun.COM suggested the following:

>You can place any instance specific data in the Window extra bytes of your
>main application window. You can allocate the necessary memory and place
>either a HANDLE or a pointer in the window extra bytes. If you place a
>handle, you must use GetWindowWord()/SetWindowWord(). If you use a pointer
>you need to use GetWindowLong()/SetWindowLong() to retrieve the pointer.
>You must also remember to tell windows that you need this extra data bytes.

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There was also a post by Peter Haller indicating a similar approach.

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I finally did solve the problem, and I used the approach outlined by Juan.
Neil's initial suggestion of graying the appropriate menu item will also 
work as it prevents a second instance from being created.  However, since 
I wanted to allow multiple instances, that approach did not apply.

The [Set/Get]WindowWord approach required my setting the cbWndExtra field
to a non-zero number when registering the window class.  During the WM_CREATE
message,  I create the necessary child windows and store the handles in this
extra space using SetWindowWord().  When my window procedure receives a 
WM_COMMAND message, I simply retrieve the child window handles.  Of course,
as this was supposed to be a Directory Search function, I have to store the
current drive and directory as well.  But this can be (and was) achieved using
a similar approach.  The code worked for upto five windows, at which point I 
got sick of testing it.

Thanks to all those who replied to my post.

Santanu


-- 
Santanu
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:: cat flames > /nev/dull                     slahiri@magnus.acs.ohio-state.edu