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Two (2) questions that I need advise on at the same time.

I have been trying to put text to a screen buffer and then to bitblt the screen buffer to the screen. It works, but I would like some advice on it.

How I place the text to the screen buffer is my question.

Am I doing this correct?

(1) Is DrawText what I should be using?
I tried to get the handle of the front buffer from its HDC,
to use it here instead of the handle of the main window, which I use here:
RECT rc;
GetClientRect(Handle_of_MainWindow, &rc);

but all attempts have failed.
(2) How do I get the handle of the front buffer if all that I have its HDC, which has not worked for me?

What I have tried:

I have the following where I draw text to a previous buffer then bitblt from a buffer to the screen. It works, I think.

I am not certain if I am doing this correct. Would you please look at it and advise me?

void Draw_From_FRONT_BUFFER_001_To_MainWindow()
        Processing_A_Buffer_Update = 1;

        HDC_of_MainWindow = GetDC( Handle_of_MainWindow ) ;

/// current attempt

    // Created earlier and saved as a Global.
    // HDC_of_FRONT_BUFFER_001 = CreateCompatibleDC( HDC_of_MainWindow );
    // The FRONT_BUFFER_001 is the same size as the MainWindow, so I am using the MainWindow handle. But it could be a different size, so what do I do for that?


    RECT rc;
    GetClientRect(Handle_of_MainWindow, &rc);

    SetTextColor(HDC_of_FRONT_BUFFER_001, RGB(255, 0, 0));
    DrawText(HDC_of_FRONT_BUFFER_001, L"Red Text on Transparent Background!", -1, &rc, DT_CENTER|DT_VCENTER|DT_WORDBREAK);

/// current attempt

        // Now copy the FRONT_BUFFER_001 to the MainWindow.
                HDC_of_MainWindow,	// destination buffer, in this case the front buffer.
                0,                  // Horizontal start for drawing.
                0,	                // Vertical   start for drawing.
                FRONT_BUFFER_001_WIDTH,       // Width to draw.
                FRONT_BUFFER_001_HEIGHT,       // Height to draw.
                HDC_of_FRONT_BUFFER_001,  // SOURCE buffer.  We are taking from that back canvas.
                0,                  // Horizontal start copying from.
                0,		            // Vertical   start copying from.
                SRCCOPY             // Just want a straight copy.

        ReleaseDC( Handle_of_MainWindow, HDC_of_MainWindow ) ;

        Processing_A_Buffer_Update = 0;

I tried to use the handle of the FRONT_BUFFER_001 so that I could write text to that buffer in case I had used a different width or height than for the MainWindow but that did not work. Here is my attempt that did not work. No text shows up.
HWND Handle_of_FrontBuffer001 = WindowFromDC(HDC_of_FRONT_BUFFER_001);

    RECT rc;
    GetClientRect(Handle_of_FrontBuffer001, &rc);

That is why I am using the handle of the main window like this
RECT rc;
GetClientRect(Handle_of_MainWindow, &rc);

Please advise.

Thank you.
Updated 18-Mar-21 20:18pm
Richard MacCutchan 19-Mar-21 6:09am
You can only update the screen when responding to a WM_PAINT message. If you do it at any other time then it will be cleared as soon as a WM_PAINT message is sent. And if you do it properly you can write direct to the main Window, you do not need BitBlt.

1 solution

Please learn some basics like frome this GDI Drawing and Printing or / and this GDI tutorial and also use the naming conventions. This helps other people to understand your code.

some tips:
- use the standard naming conventions
- work ONLY at one HDC one time
- release EVERY resource when done
- read tutorials and documentations

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