DOCERR: Region Functions Documented Incorrectly

The information in this article applies to:

• Microsoft Windows Software Development Kit (SDK) for Windows version 3.1

SUMMARY

The Microsoft Windows graphics device interface (GDI) uses two major categories of coordinates units: device units and logical units. The documentation of many GDI functions in the "Microsoft Windows Software Development Kit: Programmer's Reference, Volume 2: Functions" manual is inconsistent with regard to type of coordinates required by the functions that specify positions. This article lists these functions and the units they use.

MORE INFORMATION

The documentation for the CreateEllipticRgn (page 97), CreateEllipticRgnIndirect (pages 97 and 98), CreateRectRgn (pages 122 and 123), CreateRectRgnIndirect (pages 123 and 124), and CreateRoundRectRgn (pages 124 and 125) functions states that the parameters to each function are in logical coordinates. However, because none of these functions takes a device context (DC) as a parameter, the parameters have no units. The units are provided by the function that uses the region created.

The documentation for CreatePolygonRgn (pages 118 and 119) and CreatePolyPolygonRgn (pages 119 through 121) do not mention units; these functions are also unitless.

The documentation for the FillRgn (page 302), FrameRgn (pages 314 and 315), InvertRgn (pages 544 and 545), and PaintRgn (pages 735 and 736) functions state that the functions require device coordinates. However, these functions use logical coordinates.

The coordinates for a region used with the SelectClipRgn function must be in device units as stated in its documentation (pages 808 and 809).