MFC, Subclassing in MFC

Subclassing in MFC

Author	Message
Peter Aspe #1 / 5	Subclassing in MFC Is there any (legal) way of subclassing a window that is attached to a (CWnd-derived) MFC object? I was hoping to subclass a toolbar control (based on CToolbar and embedded in a CFrameWnd) in order to intercept notification messages from a child ComboBox, but evidently the mechanism provided by CWnd::SubclassWindow does not allow for subclassing a window that is already attached to an MFC object. Is this definitely impossible, or is there another way? If subclassing is not possible, is there another recommended approach (in MFC context) to picking up the notification messages from a ComboBox (or any other child control) sitting on a toolbar? Thanks Peter
Wed, 13 Jul 2005 18:54:40 GMT

Jeff Partc #2 / 5	Subclassing in MFC Quote: > Is there any (legal) way of subclassing a window that is attached to a > (CWnd-derived) MFC object? > I was hoping to subclass a toolbar control (based on CToolbar and embedded > in a CFrameWnd) in order to intercept notification messages from a child > ComboBox, but evidently the mechanism provided by CWnd::SubclassWindow does > not allow for subclassing a window that is already attached to an MFC > object. > Is this definitely impossible, or is there another way? If subclassing is > not possible, is there another recommended approach (in MFC context) to > picking up the notification messages from a ComboBox (or any other child > control) sitting on a toolbar? Well, there's SetWindowLongPtr/GWLP_WNDPROC, and MSJ columnist Paul DiLascia has a helper class called CSubclassWnd that he's been using since circa 1997. As good a starting point for it as any is this URL to his June 1997 C++ Q&A column... http://www.microsoft.com/msj/defaultframe.asp?page=/msj/0697/c++0697.htm -- Jeff Partch [VC++ MVP]
Wed, 13 Jul 2005 19:56:48 GMT

Ajay Kalr #3 / 5	Subclassing in MFC You should not have to subclass the toolbar for this. I think you should be able to handle the notification in mainframe or any of the CCmdTarget derived objects in routing chain. -- Ajay Kalra [MVP - VC++] Quote: > Is there any (legal) way of subclassing a window that is attached to a > (CWnd-derived) MFC object? > I was hoping to subclass a toolbar control (based on CToolbar and embedded > in a CFrameWnd) in order to intercept notification messages from a child > ComboBox, but evidently the mechanism provided by CWnd::SubclassWindow does > not allow for subclassing a window that is already attached to an MFC > object. > Is this definitely impossible, or is there another way? If subclassing is > not possible, is there another recommended approach (in MFC context) to > picking up the notification messages from a ComboBox (or any other child > control) sitting on a toolbar? > Thanks > Peter
Thu, 14 Jul 2005 07:14:50 GMT

Joseph M. Newcome #4 / 5	Subclassing in MFC Well, in addition to the other solutions proposed, you could just change the class name of the variable in the CFrameWnd. joe Quote: >Is there any (legal) way of subclassing a window that is attached to a >(CWnd-derived) MFC object? >I was hoping to subclass a toolbar control (based on CToolbar and embedded >in a CFrameWnd) in order to intercept notification messages from a child >ComboBox, but evidently the mechanism provided by CWnd::SubclassWindow does >not allow for subclassing a window that is already attached to an MFC >object. >Is this definitely impossible, or is there another way? If subclassing is >not possible, is there another recommended approach (in MFC context) to >picking up the notification messages from a ComboBox (or any other child >control) sitting on a toolbar? >Thanks >Peter Joseph M. Newcomer [MVP] Web: http://www3.pgh.net/~newcomer MVP Tips: http://www3.pgh.net/~newcomer/mvp_tips.htm
Thu, 14 Jul 2005 08:07:44 GMT

Peter Aspe #5 / 5	Subclassing in MFC Hi all Thanks for the tips. I have derived my own class from CToolBar and overridden its WindowProc. That works in any case. (Is that what Joe meant?) But then Ajay had a point too. Indeed, when I tried his suggestion, it worked! It hadn't occurred to me that MFC's message-routing mechanism would take care of it automatically. It just meant manually adding the message map entry and handler as the wizard didn't recognise this event in this context. Thanks one and all! Peter Quote: > Is there any (legal) way of subclassing a window that is attached to a > (CWnd-derived) MFC object? > I was hoping to subclass a toolbar control (based on CToolbar and embedded > in a CFrameWnd) in order to intercept notification messages from a child > ComboBox, but evidently the mechanism provided by CWnd::SubclassWindow does > not allow for subclassing a window that is already attached to an MFC > object. > Is this definitely impossible, or is there another way? If subclassing is > not possible, is there another recommended approach (in MFC context) to > picking up the notification messages from a ComboBox (or any other child > control) sitting on a toolbar? > Thanks > Peter
Thu, 14 Jul 2005 15:13:41 GMT

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