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Notify The System Of Changes

Notify The System Of Changes

A new Windows 95-only API call notifies the system that you’ve changedsomething it should know about. The call, SHChangeNotify, is very handyin a number of cases. You might make this call in twenty different cases.This tip covers a few of the most important. The call itself has only fourparameters:

  • wEventId contains the flag identifying what has changed, such as: 
     SHCNE_ASSOCCHANGED Changed a file type association. SHCNE_ATTRIBUTES Changed a file's attributes.SHCNE_CREATE Created a file.SHCNE_DELETE Deleted a file.SHCNE_MKDIR Created a new directory.SHCNE_RENAMEFOLDER Renamed a folder.SHCNE_RENAMEITEM Renamed an item in afolder.SHCNE_RMDIR Removed a directory.SHCNE_UPDATEDIR Updated the contents of a directory.SHCNE_UPDATEITEM Changed the properties of a printeror file.

    These flags let Explorer know that something it is showing on screenmight have changed and it needs to update its display.

  • uFlags indicates what the next two parameters contain. Generally, you’ll want to pass SHCNF_FLUSH so that the function doesn’treturn until it has processed the call. Instead, you may want to pass SHCNF_FLUSHNOWAITso that the call returns immediately but the system continues to processthe call in the background.
  • dwItem1 is event specific, but for the flags you can pass null forboth of these items.
  • dwItem2 is event specific.

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