IDirectManipulationManager::RegisterHitTestTarget method (directmanipulation.h)

Registers a dedicated thread for hit testing.

Syntax

HRESULT RegisterHitTestTarget(
  [in]           HWND                            window,
  [in, optional] HWND                            hitTestWindow,
  [in]           DIRECTMANIPULATION_HITTEST_TYPE type
);

Parameters

[in] window

The handle of the main app window (typically created from the UI thread).

[in, optional] hitTestWindow

The handle of the window in which hit testing is registered (should be created from the hit testing thread). Pass in nullptr to unregister a previously registered hit-test target.

[in] type

One of the values from DIRECTMANIPULATION_HITTEST_TYPE. Specifies whether the UI window or the hit testing window (or both) receives the hit testing WM_POINTERDOWN message , and in what order.

Return value

If the method succeeds, it returns S_OK. Otherwise, it returns an HRESULT error code.

Remarks

Hit testing is typically performed on the application UI thread. The application receives a WM_POINTERDOWN message on which hit-testing is performed. If a manipulation is required, SetContact is called on one or more viewports. An application can use the RegisterHitTestTarget method to delegate this hit-testing responsibility to a separate hit-testing thread.

Once a dedicated hit-test target is successfully registered, WM_POINTERDOWN messages are processed on the hit-testing thread. If a manipulation, such as pan or zoom, is required, SetContact is called from this thread.

If SetContact is not called from the hit-testing thread, WM_POINTERDOWN messages may be processed on the UI thread, depending on the DIRECTMANIPULATION_HITTEST_TYPE specified during registration.

If SetContact is not called by either the hit-test thread or the UI thread, Direct Manipulation ignores the input which is then handled on the UI thread.

Requirements

See also

IDirectManipulationManager