LVCOLUMN.cchTextMax和LVITEM.cchTextMax的目的是什么？

Question

I have tried to set the values of LVCOLUMN.cchTextMax and LVITEM.cchTextMax to a random value (less than the corresponding string length) and it worked, did it work by mistake or these fields are not necessary to set?

I have also seen examples that do not use these fields, for example: http://www.codeproject.com/Articles/9148/C-functions-to-insert-columns-items-and-subitems-i

Answer 1

The documentation for the LVITEM structure has the following to say on the cchTextMax member:

This member is only used when the structure receives item attributes. It is ignored when the structure specifies item attributes. For example, cchTextMax is ignored during LVM_SETITEM and LVM_INSERTITEM . It is read-only during LVN_GETDISPINFO and other LVN_ notifications.

Unless you are using this structure to retrieve item information, this member is ignored. When receiving data you have to pass a pointer to a buffer to pszText , and communicate its size through the cchTextMax member.

This is a common pattern throughout the Windows API, where the same structure is used to set and query values. The semantics of the individual members depend on the direction. Other common structures, that are used in a similar fashion include TVITEM or MENUITEMINFO , for example.