Tcl8.5.19/Tk8.5.19 Documentation > TkLib > GetDash



Tk_GetDash - convert from string to valid dash structure.


#include <tk.h>
Tk_GetDash(interp, string, dashPtr)


Tcl_Interp *interp (in)
Interpreter to use for error reporting.

const char * string (in)
Textual value to be converted.

Tk_Dash *dashPtr (out)
Points to place to store the dash pattern value converted from string.


These procedure parses the string and fills in the result in the Tk_Dash structure. The string can be a list of integers or a character string containing only “.,-_” or spaces. If all goes well, TCL_OK is returned. If string does not have the proper syntax then TCL_ERROR is returned, an error message is left in the interpreter's result, and nothing is stored at *dashPtr.

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 as the first position in 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 of this syntax with the previous 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 assures 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 as the first one.


dash, conversion