______________________________________________________________________________
Tk_GetDash − convert from string to valid dash structure.
#include <tk.h>
int
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. Must not be NULL. |
______________________________________________________________________________
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.
canvas(n), Tk_CreateItemType(3)
dash, conversion