IResourceManager::SetFocus
| Microsoft DirectShow 9.0 |
IResourceManager::SetFocus
The SetFocus method notifies the resource manager that a specified object has been given the focus of the user.
Syntax
HRESULT SetFocus( IUnknown *pFocusObject );
Parameters
pFocusObject
[in] Pointer to the object that has been given the user's focus.
Return Value
Returns an HRESULT value that depends on the implementation. HRESULT can be one of the following standard constants, or other values not listed.
| Return code | Description |
| E_FAIL | Failure. |
| E_POINTER | Null pointer argument. |
| E_INVALIDARG | Invalid argument. |
| E_NOTIMPL | Method isn't supported. |
| S_OK or NOERROR | Success. |
Remarks
In DirectShow, the object given the user's focus is typically a video renderer whose window has received the focus. The resource manager gives priority to requests for resources in the following order:
- Requests made with the focus object specified in the pFocusObject parameter.
- Requests whose focus object shares a common source filter.
- Requests whose focus object shares a common filter graph.
- Requests in the same process as the focus.
After a focus has been set, the resource manager must maintain a focus object until ReleaseFocus is called. That is, after calling this method, you must use ReleaseFocus before the IUnknown interface of the focus object becomes invalid, unless you can guarantee that SetFocus is called by a different object in the meantime. No reference count is held on the focus object.
The resource manager will hold this pointer until replaced or canceled, and will use it to resolve resource contention. It will use QueryInterface for the IBaseFilter interface at least and, if found, will use methods on that interface. It calls methods on IBaseFilter to decide which audio renderer to use if there are two (it will choose the one with a source filter common to the focus object), and also to determine if the two objects are within the same filter graph.
Requirements
Header: Declared in Strmif.h; include Dshow.h.
Library: Use Strmiids.lib.
See Also