[MFC] Notes for using CScrollView

CScrollView is generally used in the document view structure, which can contain pictures, tables, etc.

However, we often get confused when we start to use it.

For example, how to set the size? We know where to call SetScrollSizes? I used to call both OnInitialUpdate and OnUpdate to initialize an appropriate size in OnInitialUpdate (because SetScrollSizes is very fragile, an error occurs if the value is less than or equal to 0 ), then, adjust the View size when you open the image, that is, find the image size in OnUpdate and set it later.

I am confused about the running results, and the size has not changed! Later, it was found that OnUpdate was called by default in OnInitialUpdate, so it was changed in OnUpdate and then changed back. The effect was that SetScrollSizes in OnUpdate didn't seem to work at all.