BOOL
VC_SetOverlayOffset(
VCUSER_HANDLE vh,
PRECT prc
);
The VC_SetOverlayOffset function requests a kernel-mode video capture driver to set the overlay offset rectangle. This rectangle defines which portion of the frame buffer appears in the overlay window.
Parameters
vh
Handle to the kernel-mode driver, obtained from VC_OpenDevice.
prc
Pointer to a RECT structure containing screen coordinates that describe the offset rectangle. (The RECT structure is described in the Win32 SDK.)
Return Value
Returns TRUE if the operation succeeds. Otherwise, returns FALSE.
Comments
User-mode drivers using VCUser.lib typically call VC_SetOverlayOffset when a client sends the DVM_SRC_RECT message for the VIDEO_EXTERNALOUT channel. If the source image is larger than the overlay window, the client typically provides scroll bars to allow the user to pan across the source image, and sends DVM_SRC_RECT messages when the user scrolls the view.
The prc parameter specifies the portion of the frame buffer to send to the overlay window. The kernel-mode driver should display the top left corner of the specified offset rectangle in the top left corner of the overlay window.
The VC_SetOverlayOffset function calls DeviceIoControl (described in the Win32 SDK) to send an IOCTL_VIDC_OVERLAY_OFFSET control code to the specified kernel-mode driver. When a kernel-mode driver using VCKernel.lib receives this control code, its SetOverlayOffsetFunc function is called.