Win32：使用cchTextMax在树视图中设置文本长度

Question

Is it possible to define text length that would be displayed in the node of Tree View control in Win32 application?

For example we have string "text|2". Then I want to store pointer to this string in the node, but display only "text" without "|2".

I thought that cchTextMax field is responsible for this, but the next code won't work:

TV_INSERTSTRUCT tvinsert;
tvinsert.item.mask = TVIF_TEXT;
tvinsert.item.pszText = "text|2";
tvinsert.item.cchTextMax= 4;
SendDlgItemMessage(hDlg,IDD_TREE,TVM_INSERTITEM,0,(LPARAM)&tvinsert);

Node strill displays full text "text|2".

One solution was to copy required text to new pointer, and then use it. But this solution not satisfied me, since I need to store last part of string with node too.

Answer 1

Here is from MSDN documentation of TVITEM :

cchTextMax
Size of the buffer pointed to by the pszText member, in characters. If this structure is being used to set item attributes, this member is ignored.

So this member is only valid when you are retrieving an items attribute and ignored when you are setting it(as in adding a new item to a tree-view control). Your other solution of copying required text to new pointer, and then using is one option.

Answer 2

Strings in C are null terminated char arrays, that is, Windows will display any chars up to the first '\\0' it met, there is no way to specify length. In order to do what you want, you have to create a new string:

const char *s = "text|2";
const char str_to_display[5] = {'\0'};
strncpy(str_to_display, s, 4);

Answer 3

I would extend fluter's answer, and to insert that '\\0' right in place of the separator. A typical use of this is multi-string, where you have a set of 0-terminated string together, terminated with double '\\0' .

As a side benefit, you can use strtok() to parse your string; the (sometimes undesirable) effect of it is insertion of zeroes in place of separators.