Derived From:
Mix-in Classes:
Declared In:add-ons/input_server/InputServerFilter.h
Allocation:By the Input Server only
Class Overview

Constructor and Destructor



Creates a new BInputServerFilter object. You can initialize the object—set initial values, spawn threads, etc.—either here or in the InitCheck() function, which is called immediately after the constructor.



Deletes the BInputServerFilter object. The destructor is invoked by the Input Server only—you never delete a BInputServerFilter object from your own code. If this object has spawned its own threads or allocated memory on the heap, it must clean up after itself here.

Hook Functions


virtual filter_result Filter(BMessagemessage,

The Filter() hook function is invoked by the Input Server to filter the in-coming message. You can discard the message, allow it to pass downstream (as is or modified), or replace it with one or more other messages:

  • To discard message, implement Filter() to return B_SKIP_MESSAGE (don't delete the BMessage yourself—it's owned by the Input Server).

  • If you implement Filter() to return B_DISPATCH_MESSAGE (and if you leave outList unchanged), message is allowed to continue downstream. You're allowed to modify (but not destroy or replace) message.

  • To replace message, place one or more BMessage in outList and return B_DISPATCH_MESSAGE. message is discarded; the messages in outList are passed downstream in the order that they appear in the list. The Input Server owns all of the messages you pass back in outList, so don't delete them yourself. Note that if you want to include message in outList, you must copy the object before adding it to the list.

The default implementation returns B_DISPATCH_MESSAGE without modifying the message.


virtual status_t InitCheck();

Invoked by the Input Server immediately after the object is constructed to test the validity of the initialization. If the object is properly initialized (i.e. all required resources are located or allocated), this function should return B_OK. If the object returns non-B_OK, the object is deleted and the add-on is unloaded.

The default implementation returns B_OK.

Member Functions


status_t GetScreenRegion(BRegionregion) const;

The GetScreenRegion() function returns the screen's region in region. This is the most efficient way for an input filter to get the screen's region. The system screen saver's input filter uses this for its "sleep now"/"sleep never" corners.

GetScreenRegion() returns B_OK.

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