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The Function OnPrepareDC() |
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To draw graphics, we need to provide scale factors, and we need to change the
mapping mode from the default value, which is MM_TEXT. This can be done
in the CView::OnPrepareDC() function. The OnPrepareDC() function
is called for OnPaint(), for OnDraw(), and for OnPrint().
The OnPrepareDC() function is called in OnPaint() immediately before the call to
OnDraw(). The mapping mode is set before painting the view. If you are printing,
the same OnPrepareDC() function is called, this time immediately before the
application framework calls OnPrint(). The mapping mode is set before the
printing of the page. We want to change the mapping mode only if we are
printing, so we will call the CDC::IsPrinting() function and if we are printing,
we will then override the function and change the mapping mode. The function OnPrepareDC() has two parameters. The first is the device context. The second parameter is a pointer to a CPrintInfo structure, which is valid only if OnPrepareDC() is being called prior to printing. Test for this condition by calling the CDC function, IsPrinting(). |
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| RELATED TOPICS | |||
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Document-View
Architecture Message Routing PreCreateWindow() Function OnDraw() Function Document Template RUNTIME_CLASS Macro CView Class Print from the View Mapping Modes Serialization using CArchive class Diagnostic Helpers |
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