Tk_GetDash(3) Tk Library Procedures Tk_GetDash(3)

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NAME

Tk_GetDash - convert from string to valid dash structure.

SYNOPSIS

#include <tk.h>

int
Tk_GetDash(interp, string, dashPtr)

ARGUMENTS

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.
Must not be NULL.
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DESCRIPTION

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 ".,-_" and spaces. If all goes well,
TCL_OK is returned and a dash descriptor is stored in the variable
pointed to by dashPtr. 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 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.

SEE ALSO

canvas(n), Tk_CreateItemType(3)

KEYWORDS

dash, conversion

Tk 8.3 Tk_GetDash(3)