Visual Basic Shell Programming
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9.2 Copy Hook Handler Interface: ICopyHook
Now that we are somewhat familiar with copy hook handlers, let's talk about ICopyHook . This interface is the only interface a copy hook handler needs to implement. It contains one method, CopyCallback . Don't let the simplicity fool you, though. Implementing a copy hook handler is much more difficult than it seems at first glance (as you will soon see). As Table 9.1 shows, ICopyHook contains one method called CopyCallback . This is the only method ever called on a copy hook handler.
Table9.1. ICopyHook
| Method | Description |
|---|---|
| CopyCallback | Determines whether the shell will be allowed to move, copy, delete, or rename a folder or printer object. |
The syntax of the CopyCallback method is as follows :
UINT CopyCallback( HWND hwnd , UINT wFunc , UINT wFlags , LPCSTR pszSrcFile , DWORD dwSrcAttribs , LPCSTR pszDestFile , DWORD dwDestAttribs );
Table 9.2 lists the parameters that the shell passes to the copy hook handler and their meaning.
Table9.2. CopyCallback Parameters
| Parameter | Datatype | Description |
|---|---|---|
| hwnd | HWND | Handle to a window that the copy hook handler should use to display any user -interface elements. |
| wFunc | UINT | Operation to be performed (see Table 9.3). |
| wFlags | UINT | This value can be ignored for copy hook handlers. |
| pszSrcFile | LPCSTR/LPCWSTR | Address of a string that contains the name of the source folder or printer. |
| dwSrcAttribs | DWORD | Attributes of the source folder or printer (see Table 9.3). |
| pszDestFile | LPCSTR/LPCWSTR | Address of a string that contains the name of the destination folder or printer. |
| dwDestAttribs | DWORD | Attributes of the source folder or printer. These can be any of the file attribute flags that begin with FILE_ATTRIBUTE_* and are available from the API Viewer. |
Table9.3. wFunc Values
| Name | Description |
|---|---|
| FO_COPY | Copy |
| FO_MOVE | Move |
| FO_DELETE | Delete |
| FO_RENAME | Rename |
CopyCallback can return one of three values:
- IDYES
-
The operation is allowed.
- IDNO
-
Prevents the operation on this folder. The shell can continue with any other operations that are pending.
- IDCANCEL
-
Prevents the current operation and cancels all pending operations.
The IDL listing for both ICopyHookA and ICopyHookW is shown in Example 9.1.
Example 9.1. ICopyHook Interface
typedef enum { FO_MOVE = 0x0001, FO_COPY = 0x0002, FO_DELETE = 0x0003, FO_RENAME = 0x0004 } FO; [ uuid(000214EF-0000-0000-C000-000000000046), helpstring("ICopyHookA Interface"), odl ] interface ICopyHookA : IUnknown { HRESULT CopyCallback([in] HWND hwnd, [in] UINT wFunc, [in] UINT wFlags, [in] LPCSTRVB pszSrcFile, [in] DWORD dwSrcAttribs, [in] LPCSTRVB pszDestFile, [in] DWORD dwDestAttribs); } [ uuid(000214FC-0000-0000-C000-000000000046), helpstring("ICopyHookW Interface"), odl ] interface ICopyHookW : IUnknown { HRESULT CopyCallback([in] HWND hwnd, [in] UINT wFunc, [in] UINT wFlags, [in] LPCWSTRVB pszSrcFile, [in] DWORD dwSrcAttribs, [in] LPCWSTRVB pszDestFile, [in] DWORD dwDestAttribs); }
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