The first possible syntax is a list of integers. Each element represents the number of pixels of a line segment. Only the odd segments are drawn using the “outline” color. The other segments are drawn transparent.
The second possible syntax is a character list containing only 5 possible characters “.,-_ ”. The space can be used to enlarge the space between other line elements, and can not occur in the first position of the string. Some examples:
-dash . = -dash {2 4}
-dash - = -dash {6 4}
-dash -. = -dash {6 4 2 4}
-dash -.. = -dash {6 4 2 4 2 4}
-dash {. } = -dash {2 8}
-dash , = -dash {4 4}
The main difference between this syntax and the numeric is that it is shape-conserving. This means that all values in the dash list will be multiplied by the line width before display. This ensures that “.” will always be displayed as a dot and “-” always as a dash regardless of the line width.
On systems where only a limited set of dash patterns, the dash pattern will be displayed as the most close dash pattern that is available. For example, on Windows only the first 4 of the above examples are available; the last 2 examples will be displayed identically to the first one.