Mfc onvscroll not getting called in MDI main frame class

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I have a c++ MFC MDI based project using visual studio 2013 community. Mainframe class is derived as class CMainFrame : public CMDIFrameWndEx

In mainframe class in pre-create, the scroll bar is set as below.

C++

cs.style |= WS_VSCROLL | WS_HSCROLL;

An OnVScroll call back function has been added to receive a call back whenever the main frame scroll bar is moved. ON_WM_VSCROLL() has been added to the message map in the mainframe. We find that OnVScroll never gets called. How do we enable callbacks on OnVScroll whenever the user moves the scrollbar. Any help will be very appreciated. Thanks & Regards, Rakesh

What I have tried:

I don't know what to do. I wanted to to call SetScrollSizes any where in the mainframe class.

Posted 25-Apr-18 7:01am

Member 11380615

Updated 25-Apr-18 10:26am

KarstenK

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Richard MacCutchan 25-Apr-18 13:19pm

Have you called SetScrollSizes, and does a scroll bar appear on your window?

Member 11380615 25-Apr-18 22:02pm

Thanks Richard, Yes a scroll bar appears on the main frame window. Whenever the number of child windows and their end to end extent go beyond the MDI client area and vertical and horizontal scroll bar automatically appears.
I was not able to call SetScrollSizes since the function is not available in the main frame class.

Richard MacCutchan 26-Apr-18 2:52am

That is because the scroll bars are associated with the View windows, not the MainFrame. You need to set the scroll sizes for each individual view.

Member 11380615 26-Apr-18 9:53am

Each individual view the scroll sizes have been set.

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Jochen Arndt · Answer 1 · 2018-04-25T10:27:00

That is because CFrameWnd based classes route those message to the active view and CMDIFrameWnd traps the WS_VSCROLL and WS_HSCROLL and styles:

TN021: Command and Message Routing[^]:
The CFrameWnd class provides management of the active view. The following messages are routed through the active view:
All command messages (the active view gets first access to them).

WM_HSCROLL and WM_VSCROLL messages from sibling scroll bars (see below).

WM_ACTIVATE (and WM_MDIACTIVATE for MDI) get turned into calls to the virtual function CView::OnActivateView.

...
On a side note, there are two CWnd derived classes where the scroll bar styles specified at create time are trapped and not passed to Windows.
...
For CMDIFrameWnd the scroll bar styles you pass in to Create or LoadFrame are used to create the MDICLIENT.

So you can't use scrollbars with CFrameWnd based classes. It would be only possible by implementing your own (CWnd based) classes that must provide all the necessary MDI functionality. Due to the relationship between the MFC document and view classes you might have to create a complete new document and view implementation.

Note also that frame windows are for hosting and organising the views and usually do not require scrollbars.