Tk_GetDash(3tk) Tk Library Procedures Tk_GetDash(3tk)
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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 pat-
tern 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 repre-
sents the number of pixels of a line segment. Only the odd segments are
drawn using the “outline” color. The other segments are drawn transpar-
ent.
The second possible syntax is a character list containing only 5 possi-
ble characters “.,-_ ”. The space can be used to enlarge the space be-
tween 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 avail-
able; the last 2 examples will be displayed identically to the first
one.
SEE ALSO
canvas(3tk), Tk_CreateItemType(3tk)
KEYWORDS
dash, conversion
Tk 8.3 Tk_GetDash(3tk)
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