Inside Macintosh: QuickTime Components
Some video digitizer components can clip the output video image based on an arbitrary clipping region. Your application can determine whether a video digitizer component supports clipping by examining the digitizer information structure of the component. Specifically, if the digiOutDoesMask flag is set to 1 in the outputCapabilityFlags field of the appropriate digitizer information structure, the component supports clipping. See "The Digitizer Information Structure," for details. Your application can obtain a component's digitizer information structure by calling the VDGetDigitizerInfo function, which is described on VDGetDigitizerInfo . This section describes the functions provided to applications by components that support clipping.
Applications can use the VDSetClipState and VDGetClipState functions to enable and disable clipping, and to determine whether clipping is enabled. Applications can use the VDSetClipRgn and VDClearClipRgn functions to manipulate the clipping region. Applications can use these functions only during an active grab sequence. Applications set the initial clipping settings by calling either VDSetPlayThruDestination or VDSetPlayThruGlobalRect (described on VDSetPlayThruDestination and VDSetPlayThruGlobalRect , respectively).
The functions that manipulate clipping and clipping state operate on a clipping region in addition to the one specified by the mask passed by the VDSetPlayThruDestination and VDSetUpBuffers functions (described on VDSetPlayThruDestination and VDSetupBuffers , respectively). To determine the final clipping regions, intersect these two clippings.
The VDSetClipRgn function allows your application to define a clipping region.
pascal VideoDigitizerError VDSetClipRgn
(VideoDigitizerComponent ci,
RgnHandle clipRegion);
The VDClearClipRgn function allows your application to disable all or part of a clipping region that was previously set with the VDSetClipRgn function, which is described in the previous section.
pascal VideoDigitizerError VDClearClipRgn
(VideoDigitizerComponent ci,
RgnHandle clipRegion);
The VDSetClipState function allows applications to control whether clipping is enabled.
pascal VideoDigitizerError VDSetClipState
(VideoDigitizerComponent ci,
short clipEnable);
The VDGetClipState function allows applications to determine whether clipping is enabled.
pascal VideoDigitizerError VDGetClipState
(VideoDigitizerComponent ci,
short *clipEnable);