The Clipboard owner's OnHScrollClipboard member function is called by the Clipboard viewer when the Clipboard data has the CF_OWNERDISPLAY format and there is an event in the Clipboard viewer's horizontal scroll bar.
The owner should scroll the Clipboard image, invalidate the appropriate section, and update the scroll-bar values.
This member function is called by the framework to allow your application to handle a Windows message. The parameters passed to your function reflect the parameters received by the framework when the message was received. If you call the base-class implementation of this function, that implementation will use the parameters originally passed with the message and not the parameters you supply to the function.