FMExtensionProc info

The FMExtensionProc function is an application-defined callback function that processes menu commands and messages sent to a File Manager extension dynamic-link library (DLL).

LONG WINAPI FMExtensionProc(

HWND hwnd,	// handle to extension window
WORD wEvent,	// menu-item identifier, or message
LONG lParam	// additional message information
);

Parameters

hwnd

Identifies the File Manager window. An extension DLL should use this handle to specify the owner for any dialog box or message box that the DLL may display and to send request messages to File Manager.

wEvent

Specifies the message. This parameter can be one of the following values:

Value	Meaning
1-99	The user selected the menu item identified by this number.
FMEVENT_INITMENU	User selected the extension’s menu.
FMEVENT_LOAD	File Manager is loading the extension DLL.
FMEVENT_SELCHANGE	Selection changed in File Manager’s directory window or in Search Results window.
FMEVENT_UNLOAD	File Manager is unloading the extension DLL.
FMEVENT_USER_REFRESH	User chose the Refresh command from the Window menu.

lParam

Specifies 32 bits of additional message-specific information.

Return Values

The callback function should return the result of the message processing. The actual return value depends on the message processed.

Remarks

Whenever File Manager calls the FMExtensionProc function, it waits to refresh its directory windows (for changes in the file system) until after the function returns. This allows the extension to perform large numbers of file operations without excessive repainting by File Manager. It is not necessary for the extension to send the FM_REFRESH_WINDOWS message to notify File Manager to repaint its windows.