SetTextColor is an output call.)
For example, the framework uses these two device contexts to
implement a CMetaFileDC object that will send output to a metafile
while reading attributes from a physical device. Print preview is
implemented in the framework in a similar fashion. You can also use
the two device contexts in a similar way in your application-specific
code.
2 CClietDC 类
The CClientDC class is derived from CDC and takes care of calling the
Windows functions GetDC at construction time and ReleaseDC at
destruction time. This means that the device context associated with a
CClientDC object is the client area of a window.
3 CPaintDC 类
The CPaintDC class is a device-context class derived from CDC. It
performs a CWnd::BeginPaint at construction time and
CWnd::EndPaint at destruction time. A CPaintDC object can only be
used when responding to a WM_PAINT message, usually in your
OnPaint message-handler member function.
4 CWindowDC 类
The CWindowDC class is derived from CDC. It calls the Windows
functions GetWindowDC at construction time and ReleaseDC at
destruction time. This means that a CWindowDC object accesses the
entire screen area of a CWnd (both client and nonclient areas).
5 CMetaFileDC 类
A Windows metafile contains a sequence of graphics device interface
(GDI) commands that you can replay to create a desired image or text.
To implement a Windows metafile, first create a CMetaFileDC object.
Invoke the CMetaFileDC constructor, then call the Create member
function, which creates a Windows metafile device context and attaches
it to the CMetaFileDC object.



Next send the CMetaFileDC object the sequence of CDC GDI
commands that you intend for it to replay. Only those GDI commands
that create output, such as MoveTo and LineTo, can be used.

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