Explorer-Style Hook Procedures

You can customize an Explorer-style Open or Save As dialog box by providing a hook procedure, a custom template, or both. If you provide a hook procedure for an Explorer-style dialog box, the system creates a dialog box that is a child of the default dialog box. The hook procedure acts as the dialog procedure for the child dialog box. This child dialog box is based on the custom template, or on a default template if none is provided. For more information, see Explorer-Style Custom Templates.To enable a hook procedure for an Explorer-style Open or Save As dialog box, use the OPENFILENAME structure when you create the dialog box. Set the OFN_ENABLEHOOK and OFN_EXPLORER flags in the Flags member and specify the address of an OFNHookProc hook procedure in the lpfnHook member. If you provide a hook procedure and omit the OFN_EXPLORER flag, you must use an OFNHookProcOldStyle hook procedure and you will get the old-style user-interface. For more information, see Customizing Old-Style Dialog Boxes.

An Explorer-style hook procedure receives a variety of messages while the dialog box is open. These include the following:

·The WM_INITDIALOG message and other standard dialog box messages such as the WM_CTLCOLORDLG control color message.

·A set of WM_NOTIFY notification messages indicating actions taken by the user or other dialog box events.

·Messages for any additional controls that you defined by specifying a child dialog template.

In addition, there is a set of messages that you can send to an Explorer-style dialog box to get information or to control the behavior and appearance of the dialog box.

If you provide a hook procedure for an Explorer-style dialog box, the default dialog box procedure creates a child dialog box when the default dialog procedure is processing its WM_INITDIALOG message. The hook procedure acts as the dialog procedure for the child dialog box. At this time, the hook procedure receives its own WM_INITDIALOG message with the lParam parameter set to the address of the OPENFILENAME structure used to initialize the dialog box. After the child dialog finishes processing its own WM_INITDIALOG message, the default dialog procedure moves the standard controls, if necessary, to make room for any additional controls of the child dialog box. The default dialog procedure then sends the CDN_INITDONE notification message to the hook procedure.

The hook procedure receives WM_NOTIFY notification messages indicating actions taken by the user in the dialog box. You can use some of these messages to control the behavior of the dialog box. For example, the hook procedure receives the CDN_FILEOK message when the user chooses a filename and clicks the OK button. In response to this message, the hook procedure can use the SetWindowLong function to reject the selected name and force the dialog box to remain open.

The lParam parameter for each WM_NOTIFY message is a pointer to an OFNOTIFY structure that defines the action. The code member in the header for the OFNOTIFY structure contains one of the following notification codes.

These WM_NOTIFY messages supersede the FILEOKSTRING, LBSELCHSTRING, SHAREVISTRING, and HELPMSGSTRING registered messages used by previous versions of the Open and Save As dialog boxes. However, the hook procedure also receives the superseded message after the WM_NOTIFY message if the WM_NOTIFY processing does not use SetWindowLong to set a nonzero DWL_MSGRESULT value.

To retrieve information about the status of the dialog box or to control the behavior and appearance of the dialog box, the hook procedure can send the following messages to the dialog box.