Custom Control derived from CWnd won't paint inside CFormView Wind

=?Utf-8?B?amFzb24=?= <>
Fri, 24 Oct 2008 14:12:03 -0700
Hi all.

I'm wanting to use a CFormView in a Doc/View project that contains several
comboboxes, textboxes, and a custom control. The custom control is not
painting when I run the program.

Using the dialog resource editor, I have created a resource called
IDD_AZURE_FORM, and placed my common controls on it. In addition, I have
dropped a custom control on it, and set the following properties:

Class = CDualTreeViewerCtrl
Disabled = False
ExtendedStyle = 0x0
Group = False
Style = 0x50010000
Tabstop = True
Visible = True

Prior to this, I had created a CWnd derived window called CDualTree that
will be used for my custom control. The following code it the CDualTree

#pragma once

#define DUALTREEVIEWER_CLASSNAME _T("CDualTreeViewerCtrl")

class CDualTree : public CWnd

    virtual ~CDualTree();

    virtual void OnDraw(CDC* pDC);

    BOOL RegisterWindowClass();


The following file is the implementation file. Please note I'm registering
the window in the Constructor.




void CDualTree::OnDraw(CDC* pDC)
    // paint code omitted...

BOOL CDualTree::RegisterWindowClass()
    WNDCLASS wndcls;
    HINSTANCE hInst = AfxGetInstanceHandle();

    // Register Window Class on first time use.
    if (!(::GetClassInfo(hInst, DUALTREEVIEWER_CLASSNAME, &wndcls)))
        wndcls.lpfnWndProc = ::DefWindowProc;
        wndcls.cbClsExtra = wndcls.cbWndExtra = 0;
        wndcls.hInstance = hInst;
        wndcls.hIcon = NULL;
        wndcls.hCursor = AfxGetApp()->LoadStandardCursor(IDC_ARROW);
        wndcls.hbrBackground = (HBRUSH) (COLOR_3DFACE + 1);
        wndcls.lpszMenuName = NULL;
        wndcls.lpszClassName = DUALTREEVIEWER_CLASSNAME;

        if (!AfxRegisterClass(&wndcls))
            return FALSE;

    return TRUE;


Now, from what I have been able to find out online, the steps required to
sync these two up is the following:

From the resource editor, I generate a CFormView class using the class
wizard. I then add a member variable for my Custom Control using the Add
variable function.

The following class header for CAzureView is the result of those two actions:

#pragma once
#include "dualtree.h"

class CAzureView : public CFormView
protected: // create from serialization only

    enum{ IDD = IDD_AZURE_FORM };

// Attributes
    CAzureDoc* GetDocument() const;

// Operations

// Overrides
    virtual BOOL PreCreateWindow(CREATESTRUCT& cs);
    virtual void DoDataExchange(CDataExchange* pDX); // DDX/DDV support
    virtual void OnInitialUpdate(); // called first time after construct

// Implementation
    virtual ~CAzureView();
#ifdef _DEBUG
    virtual void AssertValid() const;
    virtual void Dump(CDumpContext& dc) const;


// Generated message map functions
    afx_msg void OnFilePrintPreview();
    afx_msg void OnRButtonUp(UINT nFlags, CPoint point);
    afx_msg void OnContextMenu(CWnd* pWnd, CPoint point);
    CDualTree m_dualTree;
    afx_msg int OnCreate(LPCREATESTRUCT lpCreateStruct);

#ifndef _DEBUG // debug version in AzureView.cpp
inline CAzureDoc* CAzureView::GetDocument() const
   { return reinterpret_cast<CAzureDoc*>(m_pDocument); }

Please note it's created the CDualTree m_dualTree member variable.

The following is the implementation file for the header:

#include "stdafx.h"
#include "Azure.h"

#include "AzureDoc.h"
#include "AzureView.h"

#ifdef _DEBUG
#define new DEBUG_NEW



// CAzureView construction/destruction

    : CFormView(CAzureView::IDD)


void CAzureView::DoDataExchange(CDataExchange* pDX)
    DDX_Control(pDX, IDC_DUALTREE, m_dualTree);

BOOL CAzureView::PreCreateWindow(CREATESTRUCT& cs)
    // TODO: Modify the Window class or styles here by modifying
    // the CREATESTRUCT cs

    return CFormView::PreCreateWindow(cs);

void CAzureView::OnInitialUpdate()

void CAzureView::OnRButtonUp(UINT nFlags, CPoint point)
    OnContextMenu(this, point);

void CAzureView::OnContextMenu(CWnd* pWnd, CPoint point)
    theApp.GetContextMenuManager()->ShowPopupMenu(IDR_POPUP_EDIT, point.x,
point.y, this, TRUE);

// CAzureView diagnostics

#ifdef _DEBUG
void CAzureView::AssertValid() const

void CAzureView::Dump(CDumpContext& dc) const

CAzureDoc* CAzureView::GetDocument() const // non-debug version is inline
    return (CAzureDoc*)m_pDocument;
#endif //_DEBUG

// CAzureView message handlers

int CAzureView::OnCreate(LPCREATESTRUCT lpCreateStruct)
    if (CFormView::OnCreate(lpCreateStruct) == -1)
        return -1;

    m_dualTree.Create(_T("CDualTreeViewerCtrl"), _T(""), WS_VISIBLE,
CRect(0,0,100,100), this, 1);

    return 0;

The code added is the called to m_dualTree.Create() in the ::OnCreate

Now, when I run the program, the view loads fine, but the CDualTree window
is not drawn in the middle of the CFormView. However, if I look at the window
with Spy++, it's actually there, it's just not being painted. A break point
on the OnDraw function is never hit.

The interesting thing is, if I remove the m_dualTree.Create call in
CAZureView::OnCreate, I still get the same behaviour, i.e. in Spy++ the
window is still there, just not being drawn.

I'm not sure if the ::OnCreate call is even needed, however I thought it was
required to set the correct styles, parent etc?

Any suggestions would be greatly appreciated!



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