Appendix C Sec3

GKS LINE BUNDLES

GKS employees the concept of line bundles, where lines may be referred to by an index; the index determines the three characteristics of plotted lines, namely, line type, thickness, and color. Line type means whether the line is solid, dotted, dashed, dashed-dotted, etc. Thickness is measured in units beginning with one; two is twice as thick as one, followed by three, three times as thick. Colors are selected using a color index; the color associated with an index can be set using the PPL+ COLOR command.

The values of these characteristics together determine the line representation. One result of bundle use is that the same line bundle index may be defined to have different representations on different devices.

On X Windows devices color is usually used to distinguish lines; in that case the line type is always solid. When Postscript hard copy is made from PPL+ metafiles, lines may be rendered as color, but on monochrome printers the only available color is black. Consequently, when output is to a monochrome printer, gksm2ps uses differing line types to distinguish lines instead of color. Lines of differing thickness are available in both PPL+ X Window output and hard copy.

The table below presents the line thickness, color index and associated default color for color devices (assuming a white background), and line type for monochrome devices, for the 19 line bundles in PPL+. On color devices, the default color of line index 1 is black if the background is white, and white if the background is black; line bundle index 19 is the background color (the color index is 0).