Drawing text on a bitmap

[Salvadoravi]

Hi all,

I wrote a simple clock that shows the time over bitmap as follows:

void CMyClock::OnPaint()
{
    CRect rect;
    GetClientRect(&rect);

    CPaintDC dc(this); // device context for painting

    CDC memDC;
    memDC.CreateCompatibleDC(&dc);
    memDC.SelectObject(m_bmpMyPic);

    memDC.TextOut(10,5, m_szCurrentTime);

    dc.BitBlt(0, 0 , 130, 39, &memDC, 0,0, SRCCOPY);
}


void CMyClock::OnTimer(UINT nIDEvent)
{
    ....
    szCurrentTime = // The current time as a string
    Invalidate();       // Show the new time  
}

Everything works fine expect that I have white background border around my clock so I've modifyed the code (the change is bold):

void CMyClock::OnPaint()
{
    CRect rect;
    GetClientRect(&rect);

    CPaintDC dc(this); // device context for painting

    CDC memDC;
    memDC.CreateCompatibleDC(&dc);
    memDC.SelectObject(m_bmpMyPic);

     pDC->SetBkMode(TRANSPARENT); 
    memDC.TextOut(10,5, m_szCurrentTime);

    dc.BitBlt(0, 0 , 130, 39, &memDC, 0,0, SRCCOPY);
}

Now I got rid off the white border but everytime I draw a text it write on top of the previous text so after few seconds everything is a mess and the time is no longer readable.

Can anyone please tell me what am I doing wrong?

[D_Drmmr]

Now I got rid off the white border but everytime I draw a text it write on top of the previous text so after few seconds everything is a mess and the time is no longer readable.

Can anyone please tell me what am I doing wrong?

Draw the background before you draw the text. You can use something like memDC.FillSolidRect(...).

[cilu]

Well, it's a bitmap, so what would you expect? You have to "erase" the previous state before you draw the current one. So you have to do as D_Drmmr said, and repaint the rect where the text is drawn before you draw the text again.

[Salvadoravi]

Guys,

I've tried,

CRect rect;
GetClientRect(&rect);

CPaintDC dc(this); // device context for painting

CDC memDC;
memDC.CreateCompatibleDC(&dc);
memDC.FillSolidRect(rect, 0x0000FF);
memDC.SelectObject(m_bmpMyPic);

memDC.SetBkMode(TRANSPARENT); 
memDC.TextOut(10,5, szCurrentTime);

dc.BitBlt(0, 0 , 130, 39, &memDC, 0,0, SRCCOPY);

I get the same result.

CRect rect;
GetClientRect(&rect);

CPaintDC dc(this); // device context for painting

CDC memDC;
memDC.CreateCompatibleDC(&dc);
dc.FillSolidRect(rect, 0x0000FF);
memDC.SelectObject(m_bmpMyPic);

memDC.SetBkMode(TRANSPARENT); 
memDC.TextOut(10,5, szCurrentTime);

dc.BitBlt(0, 0 , 130, 39, &memDC, 0,0, SRCCOPY);

Same problem + very bad flickering.

CRect rect;
GetClientRect(&rect);

CPaintDC dc(this); // device context for painting

CDC memDC;
memDC.CreateCompatibleDC(&dc);
memDC.SelectObject(m_bmpMyPic);

memDC.SetBkMode(TRANSPARENT);
memDC.FillSolidRect(rect, 0x0000FF);
memDC.TextOut(10,5, szCurrentTime);

dc.BitBlt(0, 0 , 130, 39, &memDC, 0,0, SRCCOPY);

This one works but the background is red and not a bitmap.

Can you please guide me what goes wrong??

[D_Drmmr]

This one works but the background is red and not a bitmap.

Can you please guide me what goes wrong??

It's red, because you painted it red. Please explain what you want to do.

[Marc G]

You need to create another bitmap, something as follows:
- In your onpaint, create a temporary bitmap
- blit your m_bmpMyPic bitmap to this temporary bitmap
- draw the clock on this temporary bitmap
- blit the temporary bitmap to the CPaintDC