C / C++ / MFC

SimplCodr wrote:

I have solved this in non-wizard generated applications by creating a virtual window in CMAinWin::CMainWin just after Create() is called using CDC and CBitmap.

CMainWin::CMainWin()
{
	RECT r;
	r.top = 200;
	r.left = 300;
	r.bottom = 500;
	r.right = 700;

	Create(NULL, "COM View", WS_OVERLAPPEDWINDOW, r,
			NULL, "TextMenu");

	// Load accelerator table
	if(!LoadAccelTable("TextMenu"))
		MessageBox("Cannot load accelerator table.", "Error");



	
	// Setup virtual screen for storing the view
	m_X = m_Y = 0;

	maxX = GetSystemMetrics(SM_CXSCREEN);
	maxY = GetSystemMetrics(SM_CYSCREEN);

	CClientDC dc(this);

	m_memDC.CreateCompatibleDC(&dc);
	m_bmp.CreateCompatibleBitmap(&dc, maxX, maxY - 10);
	m_memDC.SelectObject(&m_bmp);

	m_bkbrush.CreateStockObject(WHITE_BRUSH);
	m_memDC.SelectObject(&m_bkbrush);

	m_memDC.PatBlt(0, 0, maxX, maxY, PATCOPY);

	m_AnsiVarFont.CreateStockObject(ANSI_VAR_FONT);
	m_SystemFont.CreateStockObject(SYSTEM_FONT);
}

afx_msg void CMainWin::OnPaint()
{
	CPaintDC dc(this);

	dc.BitBlt(0, 0, maxX, maxY, &m_memDC, 0, 0, SRCCOPY);
}

void CMainWin::OnLButtonDblClk(UINT nFlags, CPoint point)
{
	// TODO: Add your message handler code here and/or call default
	strcpy_s(str, "Hello World");
	m_memDC.TextOutA(point.x, point.y, str, strlen(str));
	InvalidateRect(NULL);
	OnPaint();
	CFrameWnd::OnLButtonDblClk(nFlags, point);
}

Header File Stuff

class CMainWin : public CFrameWnd
{
public:

	int m_X, m_Y;
	char m_str[255];
	DCB dcb;
	CDC m_memDC;
	CBitmap m_bmp;
	CBrush m_bkbrush;
	CFont m_SystemFont, m_AnsiVarFont;
	
	HANDLE Ser1;

	CMainWin();
	
	afx_msg void OnPaint();
	
	afx_msg void OnExit();

	DECLARE_MESSAGE_MAP()
	
public:
	afx_msg int OnCreate(LPCREATESTRUCT lpCreateStruct);
public:
	afx_msg void OnLButtonDblClk(UINT nFlags, CPoint point);
private:
	CToolBar m_wndToolBar;
	CStatusBar m_wndStatusBar;
};

SimplCodr wrote:

How can I create a pointer to the device context of the current view in VS2005 created MFC single document application?

CWnd* obj = new CWnd();
obj.Create(..);
obj.paint(..);

Source File Stuff

void Ccom_testView::OnLButtonDblClk(UINT nFlags, CPoint point)
{

	// Get the extents of the screen
	maxX = GetSystemMetrics(SM_CXSCREEN);
	maxY = GetSystemMetrics(SM_CYSCREEN);

	CClientDC dc(this);
	memDC.CreateCompatibleDC(&dc);

	if (m_bmp.m_hObject == NULL)
		m_bmp.CreateCompatibleBitmap(&dc, maxX, maxY);

	memDC.SelectObject(&m_bmp);


	// This does not do what it should. Expect a white background.
	// Program Still starts with a black background
	bkBrush.CreateStockObject(WHITE_BRUSH);
	memDC.SelectObject(&bkBrush);

	CBitmap* pOldBitmap = memDC.SelectObject(&m_bmp);
	CBrush* pOldbkBrush = memDC.SelectObject(&bkBrush);
	
	// Had to set text color manually
	memDC.SetTextColor(RGB(0, 200, 100));
	memDC.SetBkColor(RGB(0,0,0));	

	wsprintf(str, "Hello World");
	memDC.TextOutA(point.x, point.y, str, strlen(str));

	memDC.SelectObject(pOldbkBrush);

	memDC.SelectObject(pOldBitmap);
	memDC.DeleteDC();

	ShowIt();

	CView::OnLButtonDblClk(nFlags, point);
}

void Ccom_testView::OnPaint()
{
	CPaintDC dc(this); // device context for painting
	// TODO: Add your message handler code here
	ShowIt();
	
	//	dc.BitBlt(0, 0, maxX, maxY, &memDC, 0, 0, SRCCOPY);
	// Do not call CView::OnPaint() for painting messages
}

bool Ccom_testView::ShowIt(void)
{
//	CDC memDC;
	CClientDC dc(this);
	CBitmap* pbmOld = NULL;

	memDC.CreateCompatibleDC(&dc);
	pbmOld = memDC.SelectObject(&m_bmp);
	
	dc.BitBlt(0, 0, maxX, maxY, &memDC, 0, 0, SRCCOPY);

	memDC.SelectObject(pbmOld);
	memDC.DeleteDC();
	
	return false;
}


Header File Stuff

class Ccom_testView : public CView
{
public:
	CDC memDC;
	CBrush bkBrush;
	CBitmap m_bmp;
	CFont m_SystemFont, m_AnsiVarFont;

protected: // create from serialization only
	Ccom_testView();
	DECLARE_DYNCREATE(Ccom_testView)

// Attributes
public:
	Ccom_testDoc* GetDocument() const;

// Operations
public:

// Overrides
public:
	virtual void OnDraw(CDC* pDC);  // overridden to draw this view
	virtual BOOL PreCreateWindow(CREATESTRUCT& cs);
protected:
	virtual BOOL OnPreparePrinting(CPrintInfo* pInfo);
	virtual void OnBeginPrinting(CDC* pDC, CPrintInfo* pInfo);
	virtual void OnEndPrinting(CDC* pDC, CPrintInfo* pInfo);

// Implementation
public:
	virtual ~Ccom_testView();
#ifdef _DEBUG
	virtual void AssertValid() const;
	virtual void Dump(CDumpContext& dc) const;
#endif

protected:

// Generated message map functions
protected:
	DECLARE_MESSAGE_MAP()
public:
	afx_msg void OnLButtonDblClk(UINT nFlags, CPoint point);
public:
	afx_msg void OnPaint();
public:
	bool ShowIt(void);
};

bool Ccom_testView::ShowIt(void)
{
//	CDC memDC;

	CClientDC dc(this);
	CBitmap* pbmOld = NULL;

	memDC.CreateCompatibleDC(&dc);
CBitmap memBmp;
memBmp.CreateCompatibleBitmap(&dc);

	pbmOld = memDC.SelectObject(&membmp);
	
	dc.BitBlt(0, 0, maxX, maxY, &memDC, 0, 0, SRCCOPY);

	memDC.SelectObject(pbmOld);
memBmp.DeleteObject();
	memDC.DeleteDC();
	
	return false;
}

1. Properly erase the background (see [^]).
2. Make your painting function (i.e. ShowIt() ) accepting as argument, a CPaintDC instead of creating its own device context.
3. Never call directly your paint function (or other drawing code, use instead InvalidateRect and UpdateWindow to force the painting happen).
4. inside the button handler just set a flag (a member variable of the class) and use it to conditionally call your painting function inside OnPaint

void Ccom_testView::OnLButtonDblClk(UINT nFlags, CPoint point)
{
  // don't put drawing stuff here
  m_showit=true;
  // the following calls force the window re-paint
  InvalidateRect(NULL);
  UpdateWindow();
  //...
}

void Ccom_testView::OnPaint()
{	
  CPaintDC dc(this); // device context for painting
  if (m_showit) 
    ShowIt(dc);
  //...
}
void Ccom_testView::ShowIt(CPaintDC & dc)
{
  // use the passed dc for drawing
}

void CComViewView::OnDraw(CDC* /*pDC*/)
{
	CComViewDoc* pDoc = GetDocument();
	ASSERT_VALID(pDoc);
	if (!pDoc)
		return;

	// TODO: add draw code for native data here
	CPaintDC dc(this);

	if(m_show)
		ShowIt(dc);
}

void CComViewView::OnLButtonDblClk(UINT nFlags, CPoint point)
{
	// TODO: Add your message handler code here and/or call default
	pos = point;
	m_show = true;
	m_userIn = true;

	InvalidateRect(NULL);
	UpdateWindow();

	CView::OnLButtonDblClk(nFlags, point);
}

void CComViewView::ShowIt(CPaintDC & dc)
{
	if(!m_userIn)return;

	maxX = GetSystemMetrics(SM_CXSCREEN);
	maxY = GetSystemMetrics(SM_CYSCREEN);

	CDC memDC;
	CBitmap m_bmp;
	
	memDC.CreateCompatibleDC(&dc);
	m_bmp.CreateCompatibleBitmap(&dc, maxX, maxY);
	memDC.SelectObject(&m_bmp);

	memDC.SetTextColor(RGB(0, 200, 100));
	memDC.SetBkColor(RGB(0,0,0));	

	wsprintf(str, "Hello World");
	memDC.TextOutA(pos.x, pos.y, str, strlen(str));

	memDC.BitBlt(0, 0, maxX, maxY, &memDC, 0, 0, SRCCOPY);
	UpdateWindow();

	// Set this false to keep from executing draw code
	// on window update
	m_userIn = false;
}

SimplCodr wrote:

void CComViewView::OnDraw(CDC* /*pDC*/)
{
CComViewDoc* pDoc = GetDocument();
ASSERT_VALID(pDoc);
if (!pDoc)
return;

// TODO: add draw code for native data here
CPaintDC dc(this);

if(m_show)
ShowIt(dc);
}

void CComViewView::OnDraw(CDC* pDC)
{
CComViewDoc* pDoc = GetDocument();
ASSERT_VALID(pDoc);
if (!pDoc)
return;

if(m_show)
ShowIt(*pDC);
}

SimplCodr wrote:

memDC.BitBlt(0, 0, maxX, maxY, &memDC, 0, 0, SRCCOPY);

dc.BitBlt(0, 0, maxX, maxY, &memDC, 0, 0, SRCCOPY);