Redrawing/refreshing a displayed bitmap in MFC?

through this post, I've managed to make pictures show up in a dialog box (great info there).

However, if I move another window over and then off of my displayed image, the displayed image doesn't redraw. Is there a way to force a redraw when it needs it? How do you determine when it needs it?

I'll post code if necessary, it just doesn't seem so in this case.

....I'm finally beginning to get up to speed with Windows programming - it ain't so bad when you get used to it.

Thanks.

The original code I posted works properly. The OnPaint() method is called whenever the window needs updating.

Post you OnPaint() code and we'll go from there.

gg

both the init and the paint:

Code:

BOOL CFloatingDlg::OnInitDialog()
{
	CDialog::OnInitDialog();
	
	SetWindowPos(NULL, 
			0, 0,
			960, 540,
			SWP_NOMOVE | SWP_NOZORDER); 

	return TRUE;  // return TRUE  unless you set the focus to a control
}

void CFloatingDlg::OnPaint()
{
	// CPaintDC dc(this); // device context for painting
	// TODO: Add your message handler code here
	// Do not call CDialog::OnPaint() for painting messages
	if (IsIconic())
	{
		CPaintDC dc(this); // device context for painting

		SendMessage(WM_ICONERASEBKGND, (WPARAM) dc.GetSafeHdc(), 0);

		// Center icon in client rectangle
		int cxIcon = GetSystemMetrics(SM_CXICON);
		int cyIcon = GetSystemMetrics(SM_CYICON);
		CRect rect;
		GetClientRect(&rect);

		int x = (rect.Width() - cxIcon + 1) / 2;
		int y = (rect.Height() - cyIcon + 1) / 2;
	}
	else
	{
        // our paint DC
        CPaintDC dc(this);

        // load up our bitmap into bmME
        CBitmap cbmME;
        
        // for resources use:
        //    cbmME.LoadBitmap(IDB_BITMAP_ME);

        // for files use this:
		HBITMAP hBmp = (HBITMAP)::LoadImage(NULL, "preview.bmp", IMAGE_BITMAP,
                                            960, 540, LR_LOADFROMFILE | LR_CREATEDIBSECTION);
        if (hBmp == NULL)
        {
			TRACE0("::LoadImage('preview.bmp') failed");
            return;
        }//if
       
	    cbmME.Attach(hBmp);
        
        // draw to dialog
        CRect framerect;
	this->GetWindowRect(framerect);
        ScreenToClient(framerect);

        // create a memory DC
        CDC dcMem;
	    dcMem.CreateCompatibleDC(&dc);

        // select the bitmap into the memory dc
        CBitmap *old = dcMem.SelectObject(&cbmME);

        // get the raw bitmap for access to its attributes
        BITMAP bm;
        cbmME.GetBitmap(&bm);

        // blit it
        dc.BitBlt(framerect.left, framerect.top, 
                  bm.bmWidth, bm.bmHeight, 
                  &dcMem, 0, 0, SRCCOPY);

        dcMem.SelectObject(old);
        ::DeleteObject(hBmp);

		CDialog::OnPaint();
	}
}

note that I changed your code so that it was no longer attaching the bitmap to the static frame, but to the dialog itself. Maybe this is the problem? (I was just noticing your use of cbmMe which is not defined in my code)... hmm.... looking at it, I have no idea what cbmME is.

Is it the title bar of the dialog that isn't redrawing properly?

gg

Originally Posted by Codeplug

Is it the title bar of the dialog that isn't redrawing properly?

gg

no, the image itself. It's rather large and resized (in half). If I drag a window over it, it does not redraw completly. see attached

Damn, is that a 6 meg bitmap I see?
You're gonna want to optimize that drawing code a bit

Add the following as member variables of the dialog:
CBitmap cbmME;
HBITMAP hBmp;
CDC dcMem;
CBitmap *old;
int bmWidth, bmHeight;

Do all the setup work in OnInitDialog(). When you call CreateCompatibleDC(x), call GetDC() for the x parameter (followed by a ReleaseDC()).

The OnPaint() should then only have to a bitblt.

Don't forget to release resources in the dialogs destructor (or OnDestroy()).

gg

Originally Posted by Codeplug

Damn, is that a 6 meg bitmap I see?
You're gonna want to optimize that drawing code a bit

Yeah, you should see the 16 bit per channel (48 bit per pixel) floating point image before it gets moved down to 8 bit per channel (24 bit per pixel) bitmap. Them's are clost to 16 MB per image & I have to deal with literally thousands of them. It's not what I'd call quick.

Thanks a ton for the info. I'll give it a try when I get back to the office.

btw, where is this info coming from? Is it just experience and/or can you recommend some online tutorials or a good book on the subject?

My first MFC book was this.
Identifying areas for optimization comes somewhat from experience.

gg