CreateWindow

The OS/2 version of CreateWindow differs from the Windows NT version where negative client areas are concerned. In Windows NT, if the client area has negative height or width, the window is drawn as though that height or width is zero. In OS/2, the absolute value of the negative space is subtracted from the surrounding border, title bar, and so on.

For example, assume that a window is to be created, and according to the parameters passed into CreateWindow:

• The bottom of the window's client area is located at 100 (device coordinates)
  
• The top of the caption is at 72 (device coordinates)

This would place the bottom of the client area at 95, depending on the height of the caption in device coordinates. In other words, the bottom of the client area is five pixels above the top.

With the same parameters, in Windows NT, a complete caption nonetheless appears on-screen when the window is created. In contrast, in OS/2, the bottom of the caption is clipped off.