Defines the type of the virtual data source callback called by SftTree/DLL to release information previously returned by the SFTTREE_VGETITEM callback.

typedef void (CALLBACK* LPFNSFTTREE_VRELEASEITEM)(
        HWND hwnd,
        SFTTREE_DWORD_PTR userData,
        int totCols,
        LONG index,
        LPSFTTREE_ITEM lpItem);

Parameters

hwnd

The window handle of the tree control.

userData

An application-specific value, as supplied in the call to VirtualInitialize using the SFTTREE_VIRTUALDEF structure.

totCols

The total number of columns defined for the tree control.

index

The zero-based index of the item to be released.

lpItem

A pointer to the SFTTREE_ITEM structure returned by the previous call to the SFTTREE_VGETITEM callback.

Comments

This callback is only used if a virtual data source has been defined using VirtualInitialize.  If items are added using AddString or InsertString, the callback is not used.

SftTree/DLL will always call SFTTREE_VRELEASEITEM before calling SFTTREE_VGETITEM for a new item, so an application can free any storage that was dynamically allocated by the callback. SFTTREE_VRELEASEITEM can be used to free any dynamically allocated memory.

The SFTTREE_ITEM structure was returned by SFTTREE_VGETITEM and can contain pointers to additional information. Any memory addressed by pointers returned in the structure must be in static memory or allocated dynamically.  All memory is managed by the called application and no memory is allocated or freed by SftTree/DLL.

This callback cannot modify the contents of the tree control in any way.  Updating the total number of items is not possible while the callback is called.

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