fail to work correctly when the bug was eliminated. The bug was an error in the return value of the GetUpdateRect() function, whereby in certain situations (where the entire window was invalid) it would return the coördinates of the update rectangle in window coordinates, rather than in logical coordinates as it was supposed to. In Windows 3.1, it always returned the update rectangle in logical coordinates. The applications that worked around the bug would perform the coordinate transform themselves to work around the bug, and end up updating the wrong parts of their windows on Windows 3.1. One graphic band and use print escapesThis is bit #2 of the compatibility bits word, with hexadecimal value 0x4, known by the symbolic name GACF_ONELANDGRXBAND in . This flag causes Windows 3.1 to use a single graphics band when printing in Landscape mode, consuming as much memory as needed for that band, and discarding whatever content would not fit into the band. Subtract clip siblingsThis is bit #14 of the compatibility bits word, with hexadecimal value 0x4000, known by the symbolic name GACF_SUBTRACTCLIPSIBS in . This flag causes Windows 3.1 to handle window invalidation differently for top-level windows that do not have the WS_CLIPSIBLINGS window style set, and their child windows. (In other words: It affects dialogue boxes and the controls on them.) With the flag set, Windows would not invalidate sibling child windows underneath (in the z-order) other WS_CLIPSIBLINGS child windows. The main reason for the flag was applications such as Lotus Notes 2.1, which implemented its own combo boxes as child windows, rather than as top-level windows (the system default combo box implementation). With this flag set, odd display problems with such windows would disappear. Support multiple printing bandsThis is bit #5 of the compatibility bits word, with hexadecimal value 0x20, known by the symbolic name GACF_MULTIPLEBANDS in . This flag causes Windows 3.1 to always use multiple bands for printing, even when one band would be sufficient. This was to work around a problem in Freelance Graphics, which would assume that if only one band existed, and it was the entire page, it was the text band, and would not even attempt to print graphics. On Windows 3.1, the universal printer driver would sometimes be able to handle both text and graphics with a single band. By forcing the use of multiple bands, the problems that this would cause for