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Subclassing dynamically created control (No ID)

Posted on 1998-12-24
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Last Modified: 2013-11-20
When creating variable numbers of controls at run-time, I generally give them an ID of NULL. However, if I wish to sub-class these controls, then they need to have an ID. Is there any way to generate a unique ID at runtime?
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Question by:murrayc
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Answers2000 earned 30 total points
ID: 1326672
Say CWnd * (or your derived class from CWnd) to the control, called pWnd

Change the id using

SetWindowLong( pWnd->m_hWnd, GWL_ID, _id_value_here ) ;

Doing this is no different from using CreateWindow with a valid id in the first place.


Now if the question is how to work out the id, they are at least 3 methods :-

Either
(a) Reserve a range of IDs that are never used for normal dialog controls( say 10000 to 10999)
Then use these up sequential.  Remember you can start again from the lowest value when the control is destroyed.

or
(b) On the Window, using EnumChildWindows to find all the other controls.  Get their id's using GetWindowLong.  Store these in a map or array.  Then set your ids to values not in the array/map

or
(c) If all your controls are dynamically created
Assign numbers sequential to your controls as they are created.  If you are worried that you might eventually run out of possible values, then keep a list of used (or unused) id's in a map (and when a windows is created/destroyed update the map), and then you re-use values when you need em.



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by:murrayc
ID: 1326673
b) Is the kind of thing I'm looking for, but what range of IDs will be acceptable?
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by:Answers2000
ID: 1326674
Anything you're not using.

Lookup at the values in resource.h

I suggest you pick a very high value, then it's easy to ensure the resource.h always uses values less than that
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