[This is preliminary documentation and subject to change.]
The IBroadcastFilter interface has three purposes: to perform the actual filtration of broadcast announcements, to provide a user interface to a filter, and to provide methods and properties necessary for the enabling, disabling, or deletion of a filter.
Every filter must support Automation and the IBroadcastFilter interface. Each filter supplies the functionality for the methods in the table following, which are called by Announcement Listener.
| Called by: | Announcement Listener |
|---|---|
| Interface definition: | Dual |
| Method | Description |
|---|---|
| Delete | Announcement Listener invokes this method to notify the filters of an announcement deletion message. |
| get_Enabled | Indicates whether Announcement Listener calls this filter. A filter may be disabled but still reside in the filter list. |
| get_Hidden | Returns a property that, if true, suppresses the display of the filter in the Filter Manager user interface. The filter still is accessible programmatically through the collection in the IDataListener. Hidden filters cannot be enabled, disabled, or removed by users. One use for a hidden filter is to listen for upgrades to the Broadcast Architecture software itself. |
| get_LastMatched | Property indicating the last time this filter selected an announcement. Used by the Filter Manager. |
| get_ListenAll | A property that, when true, causes all announcements to be presented to a filter, even if they have been matched previously by another filter. A filter with the ListenAll property set to TRUE receives all announcements, whether or not another filter has already registered to receive the associated broadcast data. This permits special filters to be created for monitoring or debugging. |
| get_Name | Returns the name of this instance of the filter. Used by the Filter Manager. |
| get_NumberMatched | The total number of announcements the filter has selected. Used by the Filter Manager. |
| GetDisposition | Returns to Announcement Listener the information it needs to schedule a future task to receive the data, including what application to launch, the working directory, the command line, and how far in advance of receipt of the data should the application be launched. |
| Match | Checks whether the announcement describes a data transmission that should be received, and if so, whether Announcement Listener should schedule a task to receive the data. Used by the Announcement Listener. |
| put_Enabled | Sets the Enabled property of the filter. |
| ShowProperties | Announcement Listener invokes this method to request the filter to display its properties (if any) in a dialog box. |