IP_SetGUIHandler

Cogent API and Utilities: Version 4.1
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# `IP_SetGUIHandler`

`IP_SetGUIHandler` -- sets callback functions for GUI events.

## Syntax

``int IP_SetGUIHandler`(IP_pfGUIFilter filter, IP_pfGUIHandler handler);`

## Arguments

`filter`

  A GUI filter function.

`handler`

  A GUI event handler function.

## Returns

`0`

## Description

This function sets the two callback functions required to deal with a GUI event through `IP_Receive`. These functions must match the following types:

        typedef int (*IP_pfGUIFilter)(int rcvid, void* msg, int length);
        typedef int (*IP_pfGUIHandler)(void* msg, int length);

The filter function returns `0` if the `rcvid`, `msg` and `length` do not represent a GUI message for this GUI, and returns non-zero if the given message is a GUI message.

The handler function must be able to process any message for which the filter function returns non-zero, routing the message to the appropriate GUI facility.

If the filter function returns non-zero, then the IP library functions will perform no further processing on that message, but will return from `IP_Receive` with a message type of `IP_GUI`. The programmer is not required to provide code for a message of type `IP_GUI`.

## See Also

Receiving Messages and Events, `IP_Receive`

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