How do I repaint my CMainFrame window?

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I have an app that is doc/view in nature and uses CMDIFrameWndEx and CMDIChildWndEx respectively.

The app uses four different document template so I change things so that the new menu will be a popup menu from which one can choose which document to lunch.The implication of this is that the client area of the main window is plain and with black (or perhaps dark grey) in colour at lunch, that is before any childframe is lunched via new or open. (clicking new or superimposed the white background of the child fram on it as expected.)

I did not like this so I overrode OnPaint so that it will render a JPEG image to the client area of the main window.

The problem is that my override works but it is immediately overridene by another code that I have not been able to track.

I see the rendered JPEG image then subsequently the black initial black background returns and stays.

How do I prevent my OnPaint operation from being overriden?
Which function/program is most likely responsible for the override?
Is such an override-causing function/program overrideable?

Posted 31-Jul-15 16:50pm

Gbenbam

Updated 31-Jul-15 17:05pm

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Sergey Alexandrovich Kryukov · Answer 1 · 2015-07-31T18:14:00

Please see my past answers:
MFC Drawed lines is disappeared[^],
Zooming Panning 2D vector graphics C++[^].

They should explain your the mechanism. You can find MFC-specific wrappers of the Windows Invalidate* API yourself.

The part "How do I prevent my OnPaint operation from being overridden?" does not seem to make much practical sense, just don't override what you don't want to override, or allow the users of your class to override what they want, because it makes a lot of sense. At the same time, I guess you need to learn this: https://msdn.microsoft.com/en-us/library/0w2w91tf.aspx[^].

[EDIT — in response to the follow-up question]

Please see my comment below on flicker, WM_ERASEBKGND and double buffering.
This CodeProject article can help you to understand further detail: Flicker Free Drawing In MFC[^].

—SA