[Dev-C++] Drawing Lines (Let's put an end to this thread)...

[David N. <dne...@mi...>]

OK, it's obvious that the person that coded:

> case WM_PAINT:
>         SetPixel(GetDC(hwnd),100,100,0x00FF0000);
>         SetPixel(GetDC(hwnd),101,100,0x00FF0000);
>         SetPixel(GetDC(hwnd),102,100,0x00FF0000);
>         SetPixel(GetDC(hwnd),103,100,0x00FF0000);
>         SetPixel(GetDC(hwnd),104,100,0x00FF0000);
>         break;

is really a newbie.  Multiple calls to GetDC() with no handle reuse, no =
ReleaseDC() calls, and trying to plot pixels rather than the =
MoveToEx()/LineTo() calls.

In case he's wondering, here's the code to do what he wanted:

case WM_PAINT:
    {
        HDC hdc;
        PAINTSTRUCT ps;
        HBRUSH hbr,oldBrush;

        hdc=3DBeginPaint(hwnd,&ps); // get the device context during a =
WM_PAINT message
        hbr =3D CreateSolidBrush(RGB(0,0,0xff)); // create a brush for =
drawing
        oldBrush =3D (HBRUSH) SelectObject(hdc,hbr); // select the brush =
into the DC
        MoveToEx(hdc,100,100,NULL); // Move to the specified position
        LineTo(hdc,104,100); // draw the line
        SelectObject(hdc,oldBrush); // select the old brush back to the =
dc
        DeleteObject(hbr); // delete our temporary brush
        EndPaint(hwnd,&ps); // end the paint session
    }
    break;

Now all of these functions are documented either in the Win32 SDK help =
file previously mentioned at =
ftp://ftp.cs.virginia.edu/pub/lcc-win32/win32hlp.exe site.

Of course there's always the definitive source at Microsoft's MSDN site: =
http://msdn.microsoft.com/library/ where you'll find all of the info =
from the Win32 help file and then some.

I would suggest that the person trying to figure out how to plot pixels =
should pick up an introductory book to programming Win32 in C/C++ =
(Charles Petzold did a marvelous job in Programming Windows 95; it's C & =
C++ (but avoids MFC), explains all about how to use the Windows API for =
drawing), and then come back when he runs into a problem...

Dave