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# Executing Viewer Commands When MCI Finishes Playing

Article ID: 114557

Article Last Modified on 8/9/2004

APPLIES TO

- Microsoft Multimedia Viewer Publishing Toolkit 2.0a

This article was previously published under Q114557

## SUMMARY

The VWRHOOK sample contains code for a HOOKS.DLL which can be used to execute Viewer commands when an MCI file within a Viewer title finishes playing. The dynamic link library (DLL) will work with MCI files which have been included in the title with an {ewX MVMCI2, ViewerMCI...} statement.

## MORE INFORMATION

The following files are available for download from the Microsoft Download Center:

Vwrhook.exe

For additional information about how to download Microsoft Support files, click the following article number to view the article in the Microsoft Knowledge Base:

119591 How to Obtain Microsoft Support Files from Online Services

Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help to prevent any unauthorized changes to the file. The DLL accomplishes this by installing a task specific WH_GETMESSAGE hook for Viewer. When an MCI file in a Viewer title finishes playing, the hook procedure will receive a MM_MCINOTIFY message. The hook procedure processes this message by sending a command to Viewer using VwrCommand().
The DLL can be used by multiple instances of Viewer because it keeps track of which instances of Viewer have called it.
To use HOOKS.DLL with a Viewer title, the title should register the functions HookMCINotify() and ChangeCommand() in the [CONFIG] section of its .MVP file as follows:

       RegisterRoutine(`hooks.dll', `HookMCINotify', `i=U')
       RegisterRoutine(`hooks.dll', `ChangeCommand', `i=S')

HookMCINotify() sets the hook. Its only parameter is the internal hwndApp variable. It returns 1 if the hook was successfully installed, and 0 otherwise. Typically, a title would call HookMCINotify(hwndApp) from the [CONFIG] section of its .MVP file (after it has been registered).
ChangeCommand() is used to set the command which should be executed when any MCI file in the title finishes playing. This command can be called from the [CONFIG] section, as a topic entry command, as a group entry or exit command, or as a hotspot command. Note that the HOOKS.DLL keeps track of only the most recent command that was set. There is no default command, so this function must be called if any command is to be executed when the hook procedure gets the MM_MCINOTIFY message. This function should only be called after HookMCINotify() has been called. ChangeCommand() takes as its parameter a string with the command in it. The string can have multiple commands, separated by semicolons (;). ChangeCommand() returns 1 if it was successful, and 0 otherwise.
A Viewer title can also register UnhookMCINotify() if it will specifically unhook the hook. It should be registered as follows:

RegisterRoutine(`hooks.dll', `UnhookMCINotify', `')

It does not take any parameters. If a title does not call this function, HOOKS.DLL will unhook the hook when the instance of Viewer that called HookMCINotify() terminates.
The sample also includes the files necessary to build a sample title which uses the DLL.

Additional query words: KBFILE

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