The extent is either the width or the height of the target, depending on the UltraSplitterUIElement.UltraSplitterUIElementDragInfoBase.SplitterOrientation. When the splitter orientation is vertical, the originalExtent represents the original width. When the splitter orientation is horizontal, the originalExtent represents the original height.
Target Platforms: Windows 10, Windows 8.1, Windows 8, Windows 7, Windows Server 2012, Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2